View source for Child development

{{Short description|Stages in the development of children}}
{{About|the developmental process|the journal|Child Development (journal){{!}}''Child Development'' (journal)}}

[[File:Walter de Maria Vertikaler Erdkilometer.jpg|thumb|A child using fingers to make a small, circular hole in the [[sand]], 1997]]
'''Child development''' involves the [[Human development (biology)|biological]], [[psychological]] and [[emotion]]al changes that occur in human beings between birth and the conclusion of [[adolescence]]. It is—particularly from birth to five years— a foundation for a prosperous and sustainable [[society]].<ref name=":0">Center on the Developing Child (2007). The Science of Early Childhood Development (InBrief). Retrieved from www.developingchild.harvard.edu.</ref>

[[Child]]hood is divided into three stages of life which include [[early childhood]], middle childhood, and late childhood ([[preadolescence]]).<ref name="Collins_1984">{{Cite book |title=Development During Middle Childhood: The Years From Six to Twelve. |collaboration=National Research Council (US) Panel to Review the Status of Basic Research on School-Age Children |date=1984 |publisher=National Academies Press (US) |veditors=Collins WA |language=en |chapter=Introduction |chapter-url=https://www.ncbi.nlm.nih.gov/books/NBK216770/}}</ref> Early childhood typically ranges from infancy to the age of 6 years old. [[Early childhood development|During this period, development]] is significant, as many of life's milestones happen during this time period such as first words, learning to crawl, and learning to walk. Middle childhood/preadolescence or ages 6–12 universally mark a distinctive period between major developmental transition points.<ref name="Collins_1984" /> Adolescence is the stage of life that typically starts around the major onset of [[puberty]], with markers such as menarche and spermarche, typically occurring at 12–14 years of age.<ref>{{Cite web |date=23 September 2021 |title=Child Development: Young Teens (12-14 years old) |url=https://www.cdc.gov/ncbddd/childdevelopment/positiveparenting/adolescence.html |website=U.S. Centers for Disease Control and Prevention (CDC)}}</ref> It has been defined as ages 10 to 24 years old by the World Happiness Report WHR.<ref name=":0" /> [[Child development stages|In the course of development]], the individual [[human]] progresses from dependency to increasing [[autonomy]]. It is a continuous process with a predictable sequence, yet has a unique course for every child. It does not always progress at the same rate and each stage is affected by the preceding developmental experiences. As genetic factors and events during prenatal life may strongly influence developmental changes, [[genetics]] and [[prenatal development]] usually form a part of the study of child development. Related terms include [[developmental psychology]], referring to development from birth to death, and [[pediatrics]], the branch of medicine relating to the care of children.

Developmental change may occur as a result of genetically controlled processes, known as [[Developmental biology|maturation]],<ref name="Toga 2006">{{Cite journal |vauthors=Toga AW, Thompson PM, Sowell ER |date=March 2006 |title=Mapping brain maturation |journal=Trends in Neurosciences |volume=29 |issue=3 |pages=148–159 |doi=10.1016/j.tins.2006.01.007 |pmc=3113697 |pmid=16472876}}</ref> or environmental factors and learning, but most commonly involves an interaction between the two. Development may also occur as a result of human nature and of human ability to learn from the environment.

There are various definitions of the periods in a child's development, since each period is a continuum with individual differences regarding starting and ending. Some age-related development periods with defined intervals include: [[newborn]] (ages 0 – 2 months); [[infant]] (ages 3 – 11 months); [[toddler]] (ages 1 – 2 years); [[preschooler]] (ages 3 – 4 years); [https://choc.org/primary-care/ages-stages/6-to-12-years/ school-aged child] (ages 5 – 12 years); [https://dictionary.cambridge.org/dictionary/english/teens#:~:text=A%20person's%20teens%20are%20the,daughters%20are%20in%20their%20teens. teens] (ages 13 – 19 years); [https://www.csap.cam.ac.uk/news/article-adolescent-brain-development/ adolescence] (ages 10 - 25 years); [https://nces.ed.gov/programs/coe/indicator/cpb/college-enrollment-rate college age] (ages 18 - 25 years).

Parents play a large role in a child's activities, socialization, and development; having multiple parents can add stability to a child's life and therefore encourage healthy development.<ref>{{Cite web |title=Parents Can Play Vital Role in Encouraging Children's Active, Healthy Lifestyles |url= https://www.cdc.gov/youthcampaign/pressroom/PDF/6.2.07-ParentsPlayRoleBG.pdf |archive-url= https://web.archive.org/web/20170620185534/https://www.cdc.gov/youthcampaign/pressroom/PDF/6.2.07-ParentsPlayRoleBG.pdf |archive-date=20 June 2017 |website=U.S. Centers for Disease Control and Prevention}}</ref> A parent-child relationship with a stable foundation creates room for a child to feel both supported and safe. This environment established to express emotions is a building block that leads to children effectively regulating emotions and furthering their development.<ref>{{Cite journal |last=Morris |first=Amanda S. |last2=Criss |first2=Michael M. |last3=Silk |first3=Jennifer S. |last4=Houltberg |first4=Benjamin J. |date=2017 |title=The Impact of Parenting on Emotion Regulation During Childhood and Adolescence |url=https://srcd.onlinelibrary.wiley.com/doi/10.1111/cdep.12238 |journal=Child Development Perspectives |language=en |volume=11 |issue=4 |pages=233–238 |doi=10.1111/cdep.12238 |issn=1750-8606|url-access=subscription }}</ref> Another influential factor in children's development is the quality of their care. [[Child-care]] programs may be beneficial for childhood development such as learning capabilities and social skills.<ref>{{cite journal | vauthors = Brundavani V, Murthy SR, Kurpad AV | title = Estimation of deep-abdominal-adipose-tissue (DAAT) accumulation from simple anthropometric measurements in Indian men and women | journal = European Journal of Clinical Nutrition | volume = 60 | issue = 5 | pages = 658–666 | date = May 2006 | pmid = 16391572 | doi = 10.2307/1602366 | jstor = 1602366 }}</ref>

The optimal development of children is considered vital to society and it is important to understand the social, cognitive, emotional, and educational development of children. Increased research and interest in this field has resulted in new theories and strategies, especially with regard to practices that promote development within the school systems. Some theories seek to describe a sequence of states that compose child development.

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== Theories ==

===Ecological systems===
{{Main|Ecological systems theory}}
Also called "development in context" or "[[human ecology]]" theory, ecological systems theory was originally formulated by [[Urie Bronfenbrenner]]. It specifies four types of nested environmental systems, with bi-directional influences within and between the systems; they are the microsystem, mesosystem, exosystem, and macrosystem. Each system contains roles, norms, and rules that can powerfully shape development. Since its publication in 1979, Bronfenbrenner's major statement of this theory, ''The Ecology of Human Development,''<ref>{{Cite book |title=The ecology of human development: experiments by nature and design |vauthors=Bronfenbrenner U |publisher=Harvard University Press |year=1979 |isbn=978-0-674-22456-8 |location=Cambridge |oclc=4515541}}</ref> has had widespread influence on the way psychologists and others approach the study of human beings and their environments. As a result of this influential conceptualization of development, these environments – from the family to economic and political structures – have come to be viewed as part of the life course from childhood through adulthood.<ref name="Smith, Cowie, Blades, 2011">{{Cite book |title=Understanding Children's Development |vauthors=Blades M, Smith PK, Cowie H |publisher=Wiley-Blackwell |year=2011 |isbn=978-1-4051-7601-9 |oclc=620124946}}</ref>

===Piaget===
{{Main|Jean Piaget|Piaget's theory of cognitive development }}
Jean Piaget was a Swiss scholar who began his studies in [[Cognitive development|intellectual development]] in the 1920s. Interested in the ways animals adapt to their environments, his first scientific article was published when he was 10 years old, and he pursued a Ph.D. in zoology, where he became interested in epistemology.<ref name="SHAFFER">{{Cite book |title=Social and personality development |vauthors=Shaffer DR |publisher=Wadsworth |year=2009 |isbn=978-0-495-60038-1 |edition=6th |location=Australia}}</ref> [[Epistemology]] branches off from philosophy and deals with the origin of knowledge, which Piaget believed came from Psychology. After travelling to Paris, he began working on the first "standardized intelligence test" at Alfred Binet laboratories, which influenced his career greatly. During this intelligence testing he began developing a profound interest in the way children's intellectualism works. As a result, he developed his own laboratory, where he spent years recording children's intellectual growth and attempting to find out how children develop through various stages of thinking. This led Piaget to develop four important stages of cognitive development: sensorimotor stage (birth to age 2), preoperational stage (age 2 to 7), concrete-operational stage (ages 7 to 12), and formal-operational stage (ages 11 to 12, and thereafter).<ref name="SHAFFER" /> Piaget concluded that adaption to an environment  (behaviour) is managed through [[Jean Piaget#Schema|schemas]] and adaption occurs through ''assimilation'' and ''accommodation''.<ref>{{Cite journal |vauthors=Huitt W, Hummel J |date=July 2003 |title=Piaget's theory of cognitive development. |url=https://www.academia.edu/download/49688242/Piagets_Theory_of_Cognitive_Development.pdf |journal=Educational Psychology Interactive |volume=3 |issue=2 |pages=1–5}}</ref>

====Stages====
{{Main article|Child development stages}}
'''Sensory Motor:''' (birth to about age 2)

In the first stage in Piaget's theory, infants have the following basic senses: vision, hearing, and motor skills. In this stage, knowledge of the world is limited but is constantly developing due to the child's experiences and interactions.<ref>{{Cite encyclopedia |title=Cognitive Development - stages, meaning, average, Definition, Description, Common problems |encyclopedia=Encyclopedia of Children's Health |url=http://www.healthofchildren.com/C/Cognitive-Development.html}}</ref> According to Piaget, when an infant reaches about 7–9 months of age they begin to develop what he called [[object permanence]], meaning the child now has the ability to understand that objects keep existing even when they cannot be seen. An example of this would be hiding the child's favorite toy under a blanket, and although the child cannot physically see it they still know to look under the blanket.<ref>{{Cite book | vauthors = Stangor C, Walinga J |date=2014-10-17 | chapter = 7.2 Infancy and Childhood: Exploring and Learning | chapter-url = https://opentextbc.ca/introductiontopsychology/chapter/6-2-infancy-and-childhood-exploring-and-learning/ | title = Introduction to Psychology | edition = 1st Canadian | publisher = BCcampus |language=en }}</ref>

'''Preoperational:''' (begins about the time the child starts to talk, around age 2)

During this stage, young children begin analyzing their environment using mental symbols, including words and images; the child will begin to apply these in their everyday lives as they come across different objects, events, and situations.<ref name="SHAFFER" /> However, Piaget's main focus on this stage, and the reason why he named it "preoperational," is that children at this point are not able to apply specific cognitive operations, such as [[Mental calculation|mental math]]. In addition to symbolism, children start to engage in [[Make believe|pretend play]], pretending to be people they are not, for example teachers or superheroes; they sometimes use different props to make this pretend play more real.<ref name="SHAFFER" /> Some weaknesses in this stage are that children who are about 3–4 years old often display what is called [[egocentrism]], meaning the child is not able to see someone else's point of view, and they feel as if every other person is experiencing the same events and feelings that they are. However, at about 7, thought processes of children are no longer egocentric and are more [[Intuition|intuitive]], meaning they now think about the way something looks, though they do not yet use [[Rationality|rational thinking.]]<ref name="SHAFFER" />

'''Concrete:''' (about first grade to early adolescence)

In this stage, children between the age of 7 and 11 use appropriate logic to develop cognitive operations and begin applying this new way of  thinking to different events they encounter.<ref name="SHAFFER" /> Children in this stage incorporate [[inductive reasoning]], which involves drawing conclusions from other observations in order to make a generalization.<ref>{{Cite web |title=Deduction & Induction |url=http://www.socialresearchmethods.net/kb/dedind.php |access-date=2017-01-24 |website=www.socialresearchmethods.net}}</ref> Unlike in the preoperational stage, children can now change and rearrange mental images and symbols to form a logical thought, an example of this is "reversibility," where the child now knows to reverse an action by doing the opposite.<ref name="SHAFFER" />

'''Formal operations:''' (around early adolescence to mid/late adolescence)

The final stage of [[Piaget's theory of cognitive development|Piaget's cognitive development]] defines a child as now having the ability to "think more rationally and systematically about abstract concepts and hypothetical events".<ref name="SHAFFER" /> Some strengths during this time are that the child or adolescent begins forming their identity and begins understanding why people behave the way they behave. While some weaknesses include the child or adolescent developing some egocentric thoughts, including the [[imaginary audience]] and the [[personal fable]].<ref name="SHAFFER" /> An imaginary audience is when an adolescent feels that the world is just as concerned and judgemental of anything the adolescent does as they themselves are; an adolescent may feel as if they are "on stage" and everyone is a critic and they are the ones being critiqued.<ref name="SHAFFER" /> A personal fable is when the adolescent feels that he or she is a unique person and everything they do is unique. They feel as if they are the only ones that have ever experienced what they are experiencing and that they are invincible and nothing bad will happen to them, bad things only happen to other people.<ref name="SHAFFER" />

===Vygotsky===
{{Main|Lev Vygotsky|Cultural-historical psychology}}
Vygotsky, a Russian theorist, proposed the sociocultural theory of child development. During the 1920s–1930s, while Piaget was developing his own theory, Vygotsky was an active scholar and at that time his theory was said to be "recent" because it was translated out of Russian and began influencing Western thinking.<ref name="SHAFFER" /> He posited that children learn through hands-on experience, as Piaget suggested. However, unlike Piaget, he claimed that timely and sensitive intervention by adults when a child is on the edge of learning a new task (called the [[zone of proximal development]]) could help children learn new tasks. This technique, called "scaffolding," builds new knowledge onto the knowledge children already have to help the child learn.<ref name="Vygotsky, 1930; Cole, 1978">{{Cite book |url=https://archive.org/details/mindinsocietydev00vygo |title=Mind in society: the development of higher psychological processes |vauthors=Cole M, Vygotskiĭ LS |publisher=Harvard University Press |year=1978 |isbn=978-0-674-57628-5 |location=Cambridge |oclc=3517053 |url-access=registration |orig-year=Published originally in Russian in 1930}}</ref> An example of this might be when a parent "helps" an infant clap or roll their hands to the [[pat-a-cake]] rhyme, until they can clap and roll their hands themself.<ref name="Vygotsky 1962 Expanded">{{Cite book |title=Thought and Language |vauthors=Kozulin A, Vygotsky LS |publisher=The MIT Press |year=2012 |isbn=978-0-262-51771-3 |location=Cambridge, Mass |oclc=768728899}}</ref><ref name="Wertsch, 1985">{{Cite book |title=Culture, communication, and cognition: Vygotskian perspectives |vauthors=Wertsch JV |publisher=Cambridge University Press |year=1985 |isbn=978-0-521-33830-1 |location=Cambridge, UK |oclc=715955821}}</ref>

Vygotsky was strongly focused on the role of culture in determining the child's pattern of development.<ref name="Vygotsky, 1930; Cole, 1978" /> He argued that "Every function in the child's cultural development appears twice: first, on the social level, and later, on the individual level; first, between people (interpsychological) and then inside the child (intrapsychological). This applies equally to voluntary attention, to logical memory, and to the formation of concepts. All the higher functions originate as actual relationships between individuals."<ref name="Vygotsky, 1930; Cole, 1978" />

Vygotsky felt that development was a process, and saw that during periods of crisis there was a qualitative transformation in the child's mental functioning.<ref name="Vygotsky, 1998">{{Cite book |title=The collected works of L. S. Vygotsky. 5, Child psychology |vauthors=Carton AS, Vygotskiĭ LS, Rieber RW |publisher=Plenum Press |year=1987 |isbn=978-0-306-45707-4 |location=New York |oclc=312913751}}</ref>

===Attachment===
{{Main|Attachment theory}}
Attachment theory, originating in the work of [[John Bowlby]] and developed by [[Mary Ainsworth]], is a [[psychological]], [[evolution]]ary and [[Ethology|ethological]] theory that provides a descriptive and explanatory framework for understanding [[interpersonal relationship]]s. Bowlby's observations led him to believe that close emotional bonds or "attachments" between an infant and their primary caregiver were an important requirement for forming "normal social and emotional development".<ref name="SHAFFER" />

===Erik Erikson===
{{Main|Erik Erikson|Psychosocial development}}
[[Erik Erikson|Erikson]], a follower of Freud, synthesized his theories with Freud's to create what is known as the [[Psychosocial development|"psychosocial"]] stages of human development. Spanning from birth to death, they focus on "tasks" at each stage that must be accomplished to successfully navigate life's challenges.<ref name="Wood, Wood, Boyd, 2010">{{Cite book |title=Mastering the World of Psychology, Books a la Carte Edition |vauthors=Boyd D, Wood SH, Wood EM |publisher=Prentice Hall |year=2010 |isbn=978-0-205-00505-5 |edition=4th |location=Englewood Cliffs, N.J |oclc=660087952}}</ref>

Erikson's eight stages consist of the following:<ref>{{Cite journal |vauthors=Manning ML |date=September 1988 |title=Erikson's Psychosocial Theories Help Explain Early Adolescence |journal=NASSP Bulletin |volume=72 |issue=509 |pages=95–100 |doi=10.1177/019263658807250914 |s2cid=144082864}}</ref>
*Trust vs. mistrust (infant)
*Autonomy vs. shame (toddlerhood)
*Initiative vs. guilt (preschooler)
*Industry vs. inferiority (young adolescent)
*Identity vs. role confusion (adolescent)
*Intimacy vs. isolation (young adulthood)
*Generativity vs. stagnation (middle adulthood)
*Ego integrity vs. despair (old age)

===Behavioral===
{{Main|Behavior analysis of child development}}
[[John B. Watson]]'s [[behaviorism]] theory forms the foundation of the [[Child development in behavior analytic theory|behavioral model of development]].<ref>{{Cite book |title=Psychologies of 1925 |vauthors=Watson JB |publisher=Clark University Press |year=1926 |veditors=Murchison E |location=Clark University, Worcester, MA, US |pages=1–35 |chapter=What the nursery has to say about instincts. |doi=10.1037/11020-001}}</ref> Watson explained human psychology through the process of [[classical conditioning]], and he believed that all individual differences in behavior were due to different learning experiences.<ref>{{Cite journal |vauthors=Watson JB, Rayner R |date=February 1920 |title=Conditioned emotional reactions. |url=http://psychclassics.yorku.ca/Watson/emotion.htm |journal=Journal of Experimental Psychology |volume=3 |issue=1 |pages=1–14 |doi=10.1037/h0069608|hdl=21.11116/0000-0001-9171-B |hdl-access=free }}</ref> He wrote extensively on child development and conducted research, such as the [[Little Albert experiment]], which showed that a phobia could be created by classical conditioning. Watson was instrumental in the modification of [[William James]]' stream of consciousness approach to construct [[Learning theory (education)|behavior theory]].<ref name="hergenhahn-2013">{{Cite book |url=https://books.google.com/books?id=6-FchL0K_ioC&q=%22stream%20of%20behavior%22%20watson&pg=PA398 |title=An Introduction to the History of Psychology |vauthors=Hergenhahn BR, Henley T |date=2013-03-01 |publisher=Cengage Learning |isbn=978-1-133-95809-3 |pages=398 |language=en}}</ref> He also helped bring a natural science perspective to child psychology by introducing objective research methods based on observable and measurable behavior.<ref name="hergenhahn-2013" /> Following Watson's lead, [[B.F. Skinner]] further extended this model to cover [[operant conditioning]] and [[verbal behavior]].<ref>{{Cite journal |vauthors=Skinner BF |date=August 1963 |title=Operant behavior. |journal=American Psychologist |volume=18 |issue=8 |pages=503–515 |doi=10.1037/h0045185 |issn=1935-990X |s2cid=51796099}}</ref> Skinner used the [[operant chamber]], or [[Skinner box]], to observe the behavior of animals in a controlled situation and proved that behaviors are influenced by the environment. Furthermore, he used reinforcement and punishment to shape the desired behavior. Children's behavior can strongly depend on their psychological development.

===Freud===
[[Sigmund Freud]] divided development, from infancy onward, into five stages.<ref>{{Cite book |title=Personality and personal growth |vauthors=Frager R, Fadiman J |date=2005 |publisher=Pearson Prentice Hall |isbn=978-0-13-144451-5 |edition=6th |location=Upper Saddle River, N.J. |oclc=57168823}}</ref> In accordance with his view that the sexual drive is a basic human motivation,<ref>{{Cite book |title=Introductory Guide to Critical Theory |vauthors=Felluga D |date=2012-12-11 |publisher=Purdue University |chapter=Modules on Freud: On Psychosexual Development |access-date=2020-12-08 |chapter-url=http://www.cla.purdue.edu/english/theory/psychoanalysis/freud.html |archive-url=https://archive.today/20121211085920/http://www.cla.purdue.edu/english/theory/psychoanalysis/freud.html |archive-date=2012-12-11 |url-status=dead}}</ref> each stage centered around the gratification of the libido within a particular area, or erogenous zone, of the body.<ref>{{Cite web |title=Freud and the Psychodynamic Perspective {{!}} Introduction to Psychology |url=https://courses.lumenlearning.com/atd-bhcc-intropsych/chapter/freud-and-the-psychodynamic-perspective/ |access-date=2020-12-08 |website=courses.lumenlearning.com}}</ref> He argued that as humans develop, they become fixated on different and specific objects throughout their stages of development.<ref>{{Cite web |title=Definition: Fixation |url=https://cla.purdue.edu/academic/english/theory/psychoanalysis/definitions/fixation.html |access-date=2020-12-08 |website=Introduction to Psychoanalysis |publisher=Purdue University |vauthors=Felluga D}}</ref><ref>{{Cite book |title=Psychoanalytic theories of development : an integration |vauthors=Tyson P, Tyson RL |date=1990 |publisher=Yale University Press |isbn=978-0-300-04578-9 |location=New Haven, CT |oclc=21197269}}</ref> Each stage contains conflict which requires resolution to enable the child to develop.<ref name="Lemma, 2007">{{Cite book |title=Handbook of individual therapy |vauthors=Lemma A |publisher=Sage |year=2002 |isbn=978-0-7619-6943-3 |veditors=Dryden W |location=Thousand Oaks, Calif |chapter=Psychodynamic Therapy: The Freudian Approach |oclc=50279223}}</ref>

===Other===
The use of [[dynamical systems theory]] as a framework for the consideration of development began in the early 1990s and has continued into the present.<ref>{{Cite book |title=A Dynamic systems approach to development applications |vauthors=Aslin RN |publisher=MIT Press |year=1993 |isbn=978-0-585-03867-4 |veditors=Thelen E, Smith LC |location=Cambridge, Mass |chapter=Commentary : the strange attractiveness of dynamic systems to development |oclc=42854628}}</ref> This theory stresses nonlinear connections (e.g., between earlier and later social assertiveness) and the capacity of a system to reorganize as a phase shift that is stage-like in nature. Another useful concept for developmentalists is the attractor state, a condition (such as teething or stranger anxiety) that helps to determine apparently unrelated behaviors as well as related ones.<ref>{{Cite book |title=Chaos: Making a New Science |vauthors=Gleick J |publisher=Penguin Books |year=1987}}</ref> Dynamic systems theory has been applied extensively to the study of motor development; the theory also has strong associations with some of Bowlby's views about attachment systems. Dynamic systems theory also relates to the concept of the transactional process,<ref>{{Cite book |title=Minimizing high-risk parenting: a review of what is known and consideration of appropriate preventive intervention |vauthors=Sameroff A |publisher=Johnson & Johnson Baby Products Company pediatric round table series |year=1983 |isbn=978-0-931562-07-5 |veditors=Hoekelman RA, Sasserath V |location=Radnor, Pa |chapter=Factors in predicting successful parenting. |oclc=8689673 |chapter-url=https://archive.org/details/minimizinghighri0000unse |chapter-url-access=registration}}</ref> a mutually interactive process in which children and parents simultaneously influence each other, producing developmental change in both over time.<ref>{{Cite journal |vauthors=Thelen E |date=2005-04-15 |title=Dynamic Systems Theory and the Complexity of Change |journal=Psychoanalytic Dialogues |volume=15 |issue=2 |pages=255–283 |doi=10.1080/10481881509348831 |issn=1048-1885 |s2cid=1327081}}</ref>

The "core knowledge perspective" is an evolutionary theory in child development that proposes "infants begin life with innate, special-purpose knowledge systems referred to as core domains of thought".<ref name="berk-2009">{{Cite book |url=https://archive.org/details/childdevelopment02berk |title=Child development |vauthors=Berk LE |publisher=Pearson Education/Allyn & Bacon |year=2009 |isbn=978-0-205-61559-9 |location=Boston |oclc=232605723 |url-access=registration}}</ref> These five domains are each crucial for survival, and prepare us to develop key aspects of early cognition, they are: physical, numerical, linguistic, psychological, and biological.<ref name="berk-2009" />

== Beginning of cognition ==

The most influential theories emphasize social interaction's essential contribution to child development from birth (e.g., the theories of Bronfenbrenner,<ref name="Smith, Cowie, Blades, 2011" /> Piaget,<ref name="SHAFFER" /> Vygotsky<ref name="Vygotsky, 1930; Cole, 1978" />). It means that organisms with simple reflexes begin to cognize the environment in collaboration with caregivers. However, different viewpoints on this issue - the [[binding problem]]<ref name="pmid10677031">{{cite journal | vauthors = Treisman A | title = Solutions to the binding problem: progress through controversy and convergence | journal = Neuron | volume = 24 | issue = 1 | pages = 105–10, 111–25 | date = September 1999 | pmid = 10677031 | doi = 10.1016/s0896-6273(00)80826-0 | doi-access = free }}</ref> and the primary data entry problem<ref name="Val Danilov 2023 Theoretical Grounds">{{cite journal |title=Theoretical Grounds of Shared Intentionality for Neuroscience in Developing Bioengineering Systems |first=Igor |last=Val Danilov |journal=OBM Neurobiology |url= https://www.lidsen.com/journals/neurobiology/neurobiology-07-01-156 |date=2023-02-17 |volume=7 |issue=1 |page=156 |doi=10.21926/obm.neurobiol.2301156|doi-access=free }}</ref><ref>Val Danilov, Igor. (2022). Smartphone in Detecting Developmental Disability in Infancy: A Theoretical Approach to Shared Intentionality for Assessment Tool of Cognitive Decline and e-Learning. K. Arai (Ed.): Proceedings of the SAI 2022, LNNS 508, pp. 1–11, 2022. Springer Nature Switzerland AG 2022 DOI: https://doi.org/10.1007/978-3-031-10467-1_19</ref> - challenge the ability of children in this stage of development to meaningfully interact with the environment.<ref name="Val_Danilov_2023">{{Cite journal | vauthors = Val Danilov I |date= 2023|title=Low-Frequency Oscillations for Nonlocal Neuronal Coupling in Shared Intentionality Before and After Birth: Toward the Origin of Perception |url=https://www.lidsen.com/journals/neurobiology/neurobiology-07-04-192 |journal=OBM Neurobiology |language=en |volume=7 |issue=4 |pages=1–17 |doi=10.21926/obm.neurobiol.2304192|doi-access=free }}</ref><ref>{{cite journal | vauthors = Val Danilov I, Mihailova S | title = A New Perspective on Assessing Cognition in Children through Estimating Shared Intentionality | journal = Journal of Intelligence | volume = 10 | issue = 2 | pages = 21 | date = March 2022 | pmid = 35466234 | pmc = 9036231 | doi = 10.3390/jintelligence10020021 | doi-access = free }}</ref>

Recent advances in neuroscience and wisdom from physiology and physics studies reconsider the knowledge gap on how social interaction provides cognition in newborns and infants. Developmental psychologist [[Michael Tomasello]] contributed to knowledge about the origins of social cognition in children by developing the notion of [[Shared intentionality]].<ref name="Tomasello_2019">{{cite book | vauthors = Tomasello M | date = 2019 | title = Becoming human: A theory of ontogeny. | location = Cambridge, Massachusetts, USA | publisher = [[Harvard University Press]] }}</ref> He posed ideas about unaware processes during social learning after birth to explain processes in shaping [[Intentionality]].<ref name="Tomasello_2019" /> Other researchers developed the notion, by observing this collaborative interaction in psychophysiological research.<ref>{{cite journal | vauthors = Val Danilov I, Mihailova S | title = Empirical Evidence of Shared Intentionality: Towards Bioengineering Systems Development. | journal = OBM Neurobiology | date = April 2023 | volume = 7 | issue = 2 | pages = 1–20 | doi = 10.21926/obm.neurobiol.2302167 | doi-access = free }}</ref><ref name="pmid28931743">{{cite journal | vauthors = McClung JS, Placì S, Bangerter A, Clément F, Bshary R | title = The language of cooperation: shared intentionality drives variation in helping as a function of group membership | journal = Proceedings. Biological Sciences | volume = 284 | issue = 1863 | pages = 20171682 | date = September 2017 | pmid = 28931743 | pmc = 5627217 | doi = 10.1098/rspb.2017.1682  }}</ref><ref>{{cite journal | vauthors = Shteynberg G, Galinsky AD | title = Implicit coordination: Sharing goals with similar others intensifies goal pursuit. | journal = Journal of Experimental Social Psychology | date = November 2011 | volume = 47 | issue = 6 | pages = 1291–1294 | doi = 10.1016/j.jesp.2011.04.012 }}.</ref>

This concept has been expanded to the intrauterine period. Research professor in bioengineering at [https://www.liepu.lv/en Liepaja University] Igor Val Danilov developed the idea of Michael Tomasello by introducing a Mother-Fetus Neurocognitive model:<ref>Val Danilov I (2024). "Child Cognitive Development with the Maternal Heartbeat: A Mother-Fetus Neurocognitive Model and Architecture for Bioengineering Systems". In: Ben Ahmed M, Boudhir AA, Abd Elhamid Attia HF, Eštoková A, Zelenáková M. (eds) ''Information Systems and Technological Advances for Sustainable Development. DATA 2024. Lecture Notes in Information Systems and Organisation,'' vol 71. Springer, Cham. https://doi.org/10.1007/978-3-031-75329-9_24 </ref> a hypothesis of neurophysiological processes occurring during [[Shared intentionality]].<ref name="Val Danilov 2023 Theoretical Grounds" /><ref name="Val_Danilov_2023" /><ref>{{Cite journal | vauthors = Val Danilov I |date= 2023|title=Shared Intentionality Modulation at the Cell Level: Low-Frequency Oscillations for Temporal Coordination in Bioengineering Systems |url=https://www.lidsen.com/journals/neurobiology/neurobiology-07-04-185 |journal=OBM Neurobiology |language=en |volume=7 |issue=4 |pages=1–17 |doi=10.21926/obm.neurobiol.2304185|doi-access=free }}</ref> It explains the onset of childhood development, describing this cooperative interaction at different levels of bio-system complexity, from interpersonal dynamics to neuronal interactions.<ref name="Val_Danilov_2023" /> The [[Shared intentionality]] hypothesis argues that nervous system synchronization provides non-local neuronal coupling in a mother-child pair, contributing to the proper development of the child's nervous system from the embryo onward.<ref name="Val_Danilov_2023" /> From the cognitive development perspective, this non-local neuronal coupling enables the mother to indicate the relevant sensory stimulus of an actual cognitive problem to the child, helping the child to grasp the perception of the object.<ref name="Val_Danilov_2023" /> This prerequisite of Shared intentionality, the pre-perceptual multimodal integration, succeeds owing to neuronal coherence in the mother-fetus biosystem beginning from pregnancy.<ref name="Reflexes Cognition" >Val Danilov I, Mihailova S (2025). "Reflexes and Shared Intentionality in the Origins of Emotions Development: A Scoping Review of Studies on Blinking in Infants". ''OBM Neurobiology'' 2025; 9(1): 263; doi:10.21926/obm.neurobiol.2501263 , https://www.lidsen.com/journals/neurobiology/neurobiology-09-01-263.</ref> These cognitive-reflex and emotion-reflex stimuli conjunctions further form innate neuronal assemblies, shaping the cognitive and emotional neuronal patterns in statistical learning that, as empirical evidence has shown, are continuously connected with the neuronal pathways of reflexes.<ref name="Reflexes Cognition" /> The natural neurostimulation of the mother's heart on the embryonal nervous system ensures the balanced architecture of the nervous system with the necessary cognitive functions corresponding to the ecological context.<ref name="Val Danilov Origin Neurostimulation_2024">Val Danilov I (2024). "The Origin of Natural Neurostimulation: A Narrative Review of Noninvasive Brain Stimulation Techniques". ''OBM Neurobiology'' 2024; 8(4): 260; doi:10.21926/obm.neurobiol.2404260 , https://www.lidsen.com/journals/neurobiology/neurobiology-08-04-260 .</ref> Electromagnetic properties of the mother's heart and its interaction with the mother's own and fetal nervous system (physical laws of electromagnetic interference) form neuronal coherence in the mother-fetus bio-system, providing the template beginning from pregnancy.<ref name="Reflexes Cognition" />

A growing body of evidence in neuroscience supports the [[Shared intentionality]] approach. Hyperscanning research studies show inter-brain coordinated activity under conditions without communication in pairs while subjects are solving a shared cognitive task<ref name="pmid37563301">{{cite journal | vauthors = Liu J, Zhang R, Xie E, Lin Y, Chen D, Liu Y, Li K, Chen M, Li Y, Wang G, Li X | display-authors = 6 | title = Shared intentionality modulates interpersonal neural synchronization at the establishment of communication system | journal = Communications Biology | volume = 6 | issue = 1 | pages = 832 | date = August 2023 | pmid = 37563301 | pmc = 10415255 | doi = 10.1038/s42003-023-05197-z }}</ref><ref name="pmid34188170">{{cite journal | vauthors = Painter DR, Kim JJ, Renton AI, Mattingley JB | title = Joint control of visually guided actions involves concordant increases in behavioural and neural coupling | journal = Communications Biology | volume = 4 | issue = 1 | pages = 816 | date = June 2021 | pmid = 34188170 | pmc = 8242020 | doi = 10.1038/s42003-021-02319-3 }}</ref><ref name="pmid29292232">{{cite journal | vauthors = Hu Y, Pan Y, Shi X, Cai Q, Li X, Cheng X | title = Inter-brain synchrony and cooperation context in interactive decision making | journal = Biological Psychology | volume = 133 | issue =  | pages = 54–62 | date = March 2018 | pmid = 29292232 | doi = 10.1016/j.biopsycho.2017.12.005 | s2cid = 46859640 }}</ref><ref name="pmid30060130">{{cite journal | vauthors = Fishburn FA, Murty VP, Hlutkowsky CO, MacGillivray CE, Bemis LM, Murphy ME, Huppert TJ, Perlman SB | display-authors = 6 | title = Putting our heads together: interpersonal neural synchronization as a biological mechanism for shared intentionality | journal = Social Cognitive and Affective Neuroscience | volume = 13 | issue = 8 | pages = 841–849 | date = September 2018 | pmid = 30060130 | pmc = 6123517 | doi = 10.1093/scan/nsy060 }}</ref><ref name="pmid28284802">{{cite journal | vauthors = Szymanski C, Pesquita A, Brennan AA, Perdikis D, Enns JT, Brick TR, Müller V, Lindenberger U | display-authors = 6 | title = Teams on the same wavelength perform better: Inter-brain phase synchronization constitutes a neural substrate for social facilitation | journal = NeuroImage | volume = 152 | issue =  | pages = 425–436 | date = May 2017 | pmid = 28284802 | doi = 10.1016/j.neuroimage.2017.03.013 | hdl = 11858/00-001M-0000-002D-059A-1 | s2cid = 3807834 | hdl-access = free }}</ref><ref name="pmid20480221">{{cite journal | vauthors = Astolfi L, Toppi J, De Vico Fallani F, Vecchiato G, Salinari S, Mattia D, Cincotti F, Babiloni F | display-authors = 6 | title = Neuroelectrical hyperscanning measures simultaneous brain activity in humans | journal = Brain Topography | volume = 23 | issue = 3 | pages = 243–256 | date = September 2010 | pmid = 20480221 | doi = 10.1007/s10548-010-0147-9 | s2cid = 3488268 }}</ref> This increased inter-brain activity is observed in pairs, which differs from the result in the condition where subjects solve a similar task alone. The significance of this knowledge is that although [[Shared intentionality]] enables social cooperation to be achieved in the unaware condition (unconsciously), it constitutes society. While this social interaction modality facilitates child development, it also contributes to grasping social norms and shaping individual values in children.<ref>"David E. Rumelhart Prize". CognitiveScienceSociety.org. Cognitive Science Society. 2022. [https://cognitivesciencesociety.org/rumelhart-prize/ "2022 Recipient – Michael Tomasello"] section. Retrieved 12 January 2024.</ref>

== Continuity and discontinuity ==

Although the identification of developmental milestones is of interest to researchers and caregivers, many aspects of development are continuous and do not display noticeable milestones.<ref name="Patterson, 2008">{{Cite book |url=https://archive.org/details/childdevelopment0000patt |title=Child development |vauthors=Patterson C |publisher=McGraw-Hill Higher Education |year=2008 |isbn=978-0-07-234795-1 |location=Boston |oclc=179102376 |url-access=registration}}</ref> Continuous changes, like growth in stature, involve fairly gradual and predictable progress toward adult characteristics. When developmental change is discontinuous, however, researchers may identify not only milestones of development, but related age periods often called stages. These stages are periods of time, often associated with known age ranges, during which a behavior or physical characteristic is qualitatively different from what it is at other ages. When an age period is referred to as a stage, the term implies not only this qualitative difference, but also a predictable sequence of developmental events, such that each stage is preceded and followed by specific other periods associated with characteristic behavioral or physical qualities.<ref name="gross">{{Cite book |title=Introducing Erik Erikson |vauthors=Gross J |date=1987 |publisher=University Press of America |isbn=978-0-8191-5788-1 |location=Lanham, MD}}</ref>

Stages of development may overlap or be associated with specific other aspects of development, such as speech or movement. Even within a particular developmental area, transition into a stage may not mean that the previous stage is completely finished. For example, in Erikson's  stages, he suggests that a lifetime is spent in reworking issues that were originally characteristic of a childhood stage.<ref name="Erikson, 1968">{{Cite book |url=https://archive.org/details/identityyouthcri00erik |title=Identity: youth, and crisis |vauthors=Erikson EH |publisher=W.W. Norton |year=1968 |isbn=978-0-393-31144-0 |location=New York |oclc=750885788 |url-access=registration}}</ref> Similarly, the theorist of cognitive development, [[Piaget's theory of cognitive development|Piaget]], described situations in which children could solve one type of problem using mature thinking skills, but could not accomplish this for less familiar problems, a phenomenon he called horizontal decalage.<ref name="mercer">{{Cite book |url=https://archive.org/details/infantdevelopmen0000merc |title=Infant Development: A Multidisciplinary Introduction |vauthors=Mercer J |publisher=Brooks/Cole |year=1998 |isbn=978-0-534-33977-7 |location=Pacific Grove, CA}}</ref>

=== Mechanisms ===
[[File:Guilianamoreno.jpg|thumb|200 px| [[Girl]] playing in a playground]]
{{See also|Nature versus nurture}}
Although developmental change runs parallel with chronological age,<ref name="feldman">{{Cite book |title=Development across the life span |vauthors=Feldman RS |date=2011 |publisher=Prentice Hall |isbn=978-0-205-80591-4 |edition=6th |location=Upper Saddle River, NJ}}</ref> age itself cannot cause development.<ref name="feldman" /> The basic causes for developmental change are genetic and environmental factors.<ref>{{Cite journal |vauthors=Plomin R, Asbury K |year=2005 |title=Nature and Nurture: Genetic and Environmental Influences on Behavior |journal=Annals of the American Academy of Political and Social Science |volume=600 |pages=86–98 |doi=10.1177/0002716205277184 |jstor=25046112 |s2cid=20315503}}</ref> Genetic factors are responsible for cellular changes like overall growth, changes in proportion of body and brain parts,<ref name="Tau 2010">{{Cite journal |vauthors=Tau GZ, Peterson BS |date=January 2010 |title=Normal development of brain circuits |journal=Neuropsychopharmacology |volume=35 |issue=1 |pages=147–168 |doi=10.1038/npp.2009.115 |pmc=3055433 |pmid=19794405}}</ref> and the maturation of aspects of function such as vision and dietary needs.<ref name="feldman" /> Because genes can be "turned off" and "turned on",<ref name="feldman" /> the individual's initial genotype may change in function over time, giving rise to further developmental change. Environmental factors affecting development may include both diet and disease exposure, as well as social, emotional, and cognitive experiences.<ref name="feldman" /> However, examination of environmental factors also shows that children can survive a fairly broad range of environmental experiences.<ref name="mercer" />

Rather than acting as independent mechanisms, genetic and environmental factors often interact to cause developmental change.<ref name="feldman" /> Some aspects of child development are notable for their [[Neuroplasticity|plasticity]], or the extent to which the direction of development is guided by environmental factors as well as initiated by genetic factors.<ref name="feldman" /> When an aspect of development is strongly affected by early experience, it is said to show a high degree of [[Neuroplasticity|plasticity]]; when the genetic make-up is the primary cause of development, plasticity is said to be low.<ref name="buchwald">{{Cite book |title=Infant Stimulation |vauthors=Buchwald J |publisher=Johnson & Johnson |year=1987 |isbn=978-0-931562-15-0 |veditors=Gunzenhauser N |location=Skillman NJ |chapter=A comparison of plasticity in sensory and cognitive processing systems}}</ref> Plasticity may involve guidance by endogenous factors like [[hormone]]s as well as by exogenous factors like infection.<ref name="feldman" /> [[File:Soapbubbles-SteveEF.jpg|thumb|left|Child playing with bubbles]]

One way the environment guides development is through experience-dependent plasticity, in which behavior is altered as a result of learning from the environment. Plasticity of this type can occur throughout the lifespan and involve many kinds of behavior, including some emotional reactions.<ref name="feldman" /> A second type of plasticity, experience-expectant plasticity, involves the strong effect of specific experiences during limited sensitive periods of development.<ref name="feldman" /> For example, the coordinated use of two eyes, and the experience of a single three-dimensional image rather than the two-dimensional images created by each eye, depends on experiences with vision during the second half of the first year of life.<ref name="feldman" /> Experience-expectant plasticity works to fine-tune aspects of development that cannot proceed to optimum outcomes as a result of genetic factors alone.<ref name="Greenoug, 1987">{{Cite journal |vauthors=Greenough WT, Black JE, Wallace CS |date=June 1987 |title=Experience and brain development |url=http://tm.ermarian.net/Academic%20Junk/Psychology/Neuroscience/Learning/Greenough,%20W.,%20Black,%20J.,%20Wallace%20C.%20%281987%29%20-%20Experience%20and%20Brain%20Development.pdf |url-status=dead |journal=Child Development |volume=58 |issue=3 |pages=539–559 |doi=10.2307/1130197 |jstor=1130197 |pmid=3038480 |archive-url=https://web.archive.org/web/20170810053121/http://tm.ermarian.net/Academic%20Junk/Psychology/Neuroscience/Learning/Greenough,%20W.,%20Black,%20J.,%20Wallace%20C.%20(1987)%20-%20Experience%20and%20Brain%20Development.pdf |archive-date=2017-08-10 |access-date=2012-08-04}}</ref><ref name="Johnson, 1993">{{Cite book |chapter-url=https://archive.org/details/braindevelopment0000unse/page/319 |title=Brain Development and Cognition |vauthors=Greenough W, Black J, Wallace C |publisher=Blackwell |year=1993 |isbn=978-0-631-18222-1 |veditors=Johnson M |location=Oxford |pages=[https://archive.org/details/braindevelopment0000unse/page/319 319–322] |chapter=Experience and brain development |oclc=25874371}}</ref>

In addition to plasticity, genetic-environmental correlations may function in several ways to determine the mature characteristics of the individual. Genetic-environmental correlations are circumstances in which genetic factors interact with the environment to make certain experiences more likely to occur.<ref name="feldman" /> In passive genetic-environmental correlation, a child is likely to experience a particular environment because his or her parents' genetic make-up makes them likely to choose or create such an environment.<ref name="feldman" /> In evocative genetic-environmental correlation, the child's genetically produced characteristics cause other people to respond in certain ways, providing a different environment than might occur for a genetically different child;<ref name="feldman" /> for instance, a child with [[Down syndrome]] may be protected more and challenged less than a child without Down syndrome.<ref name="feldman" /> Finally, an active genetic-environmental correlation is one in which the child chooses experiences that in turn have their effect,<ref name="feldman" /> for instance, a muscular, active child may choose after-school sports experiences that increase athletic skills, but may forgo music lessons. In all of these cases, it becomes difficult to know whether the child's characteristics were shaped by genetic factors, by experiences, or by a combination of the two.<ref name="berk">{{Cite book |url=https://archive.org/details/infantschildrena00berk_0 |title=Infants, Children, and Adolescents |vauthors=Berk L |publisher=Allyn & Bacons |year=2005 |isbn=978-0205511389 |location=Boston}}</ref>

=== Asynchronous development ===
Asynchronous development occurs in cases when a child's cognitive, physical, and/or emotional development occur at different rates. This is common for gifted children when their cognitive development outpaces their physical and/or emotional maturity, such as when a child is academically advanced and skipping school grade levels yet still cries over childish matters and/or still looks their age. Asynchronous development presents challenges for schools, parents, siblings, peers, and the children themselves, such as making it hard for the child to fit in or frustrating adults who have become accustomed to the child's advancement in other areas.<ref>{{Cite journal |vauthors=Rubenstein LD, Schelling N, Wilczynski SM, Hooks EN |date=October 2015 |title=Lived experiences of parents of gifted students with autism spectrum disorder: The struggle to find appropriate educational experiences. |journal=Gifted Child Quarterly |volume=59 |issue=4 |pages=283–298 |doi=10.1177/0016986215592193 |s2cid=146380252}}</ref>

== Research issues and methods ==
Research questions include:
# What develops? What relevant aspects of the individual change over a period of time?
# What are the rate and speed of development?
# What are the mechanisms of development – what aspects of experience and heredity cause developmental change?
# Are there typical individual differences in the relevant developmental changes?
# Are there population differences in this aspect of development (for example, differences in the development of boys and of girls)?

[[Empirical research]] that attempts to answer these questions may follow a number of patterns. Initially, [[Observational techniques|observational research]] in naturalistic conditions may be needed to develop a narrative describing and defining an aspect of developmental change, such as changes in reflex reactions in the first year.<ref>{{Cite web |title=Newborn Reflexes |url=https://www.healthychildren.org/English/ages-stages/baby/Pages/Newborn-Reflexes.aspx |access-date=2017-01-24 |website=HealthyChildren.org}}</ref> Observational research may be followed by [[correlation]]al studies, which collect information about chronological age and some type of development, such as increasing vocabulary; such studies examine the characteristics of children at different ages.<ref>{{Cite book |title=Research in psychology: Methods and design |vauthors=Goodwin CJ |publisher=Wiley |year=2009}}</ref> Other methods may include [[Longitudinal study|longitudinal studies]], in which a group of children is re-examined on a number of occasions as they get older; [[Cross-sectional study|cross-sectional studies]], where groups of children of different ages are tested once and compared with each other; or there may be a combination of these approaches. Some child development studies that examine the effects of experience or heredity by comparing characteristics of different groups of children cannot use a [[Randomized controlled trial|randomized design]]; while other studies use randomized designs to compare outcomes for groups of children who receive different interventions or educational treatments.<ref name="mercer" />

=== Infant research methods ===
When conducting psychological research on infants and children, certain key aspects need to be considered.<ref name="siegler-2020">{{Cite book |url=https://www.worldcat.org/oclc/1137233012 |title=How children develop |vauthors=Siegler RS, Gershoff ET, Saffran J, Eisenberg N, Leaper C |date=2020 |isbn=978-1-319-18456-8 |edition=Sixth |location=New York, New York | publisher = Worth Publishers, Macmillan Learning |oclc=1137233012}}</ref> These include that infants cannot talk, have a limited behavioral repertoire, cannot follow instructions, have a short attention span, and that, due to how rapidly infants develop, methods need to be updated for different ages and developmental stages.<ref name="siegler-2020" />

High-amplitude sucking technique (HAS) is a common way to explore infants' preferences, and is appropriate from birth to four months since it takes advantage of infants' [[sucking reflex]].<ref>{{Cite encyclopedia |encyclopedia=Encyclopedia of Language Development |publisher=SAGE Publications, Inc. |location=Thousand Oaks |url=http://swbplus.bsz-bw.de/bsz409129410inh.htm |access-date=2022-05-08 |date=2014 |pages=263–264 |doi=10.4135/9781483346441 |isbn=978-1-4522-5876-8 |vauthors=Byers-Heinlein K |chapter=High-Amplitude Sucking Procedure |chapter-url=https://sk.sagepub.com/reference/encyclopedia-of-language-development/n83.xml}}</ref> When this is being measured, researchers will code a baseline sucking rate for each baby before exposing them to the item of interest. A common finding of HAS shows a relaxed, natural sucking rate when exposed to something the infant is familiar with, like their mother's voice, compared to an increased sucking rate around novel stimuli.<ref>{{Cite journal |vauthors=Butler SC, O'Sullivan LP, Shah BL, Berthier NE |date=November 2014 |title=Preference for infant-directed speech in preterm infants |journal=Infant Behavior & Development |volume=37 |issue=4 |pages=505–511 |doi=10.1016/j.infbeh.2014.06.007 |pmid=25009957}}</ref>

The [[Preferential looking|preferential-looking technique]] was a breakthrough made by [[Robert L. Fantz]] in 1961.<ref name="siegler-2020" /> In his experiments, he would show the infants in his study two different stimuli. If an infant looks at one image longer than the other, there are two things that can be inferred: the infant can see that they are two different images and that the infant is showing preference to one image in some capacity. Depending on the experiment, infants may prefer to look at the novel and more interesting stimulus or they may look at the more comforting and familiar image.<ref>{{Cite journal |vauthors=Matsuda YT, Okamoto Y, Ida M, Okanoya K, Myowa-Yamakoshi M |date=October 2012 |title=Infants prefer the faces of strangers or mothers to morphed faces: an uncanny valley between social novelty and familiarity |journal=Biology Letters |volume=8 |issue=5 |pages=725–728 |doi=10.1098/rsbl.2012.0346 |pmc=3440980 |pmid=22696289}}</ref>

[[Eye tracking]] is a straightforward way of looking at infants' preferences. Using an eye tracking software, it is possible to see if infants understand commonly used nouns by tracking their eyes after they are cued with the target word.<ref>{{Cite journal |vauthors=Bergelson E, Swingley D |date=February 2012 |title=At 6-9 months, human infants know the meanings of many common nouns |journal=Proceedings of the National Academy of Sciences of the United States of America |volume=109 |issue=9 |pages=3253–3258 |bibcode=2012PNAS..109.3253B |doi=10.1073/pnas.1113380109 |jstor=41506937 |pmc=3295309 |pmid=22331874 |doi-access=free}}</ref>[[File:Yancey_Habituation.png|thumb|Typical pattern of habituation]]
Another unique way to study infants' cognition is through [[habituation]], which is the process of repeatedly showing a stimulus to an infant until they give no response.<ref name="daum-2017">{{Cite book |title=Cognitive development during infancy |vauthors=Daum MM |publisher=Cambridge University Press |year=2017 |veditors=Hopkins B, Geangu E, Linkenauger S |pages=277–287}}</ref> Then, when infants are presented with a novel stimulus, they show a response, which reveals patterns of cognition and perception.<ref name="daum-2017" /> Using this study method, many different cognitive and perceptual ideas can be studied. Looking time, a common measure of habituation, is studied by recording how long an infant looks at a stimulus before they are habituated to it. Then, researchers record if an infant becomes [[Dishabituation|dishabituated]] to a novel stimulus. This method can be used to measure preferences infants, including preferences for colors,<ref>{{Cite journal |vauthors=Skelton AE, Franklin A |date=February 2020 |title=Infants look longer at colours that adults like when colours are highly saturated |journal=Psychonomic Bulletin & Review |volume=27 |issue=1 |pages=78–85 |doi=10.3758/s13423-019-01688-5 |pmc=7000485 |pmid=31848908 |s2cid=209407243}}</ref> and other discriminatory tasks, such as auditory discrimination between different musical excerpts.<ref>{{Cite journal |vauthors=Flom R, Pick AD |date=December 2012 |title=Dynamics of infant habituation: infants' discrimination of musical excerpts |journal=Infant Behavior & Development |volume=35 |issue=4 |pages=697–704 |doi=10.1016/j.infbeh.2012.07.022 |pmid=22982268}}</ref>

Another way of studying children is through brain imaging technology, such as [[Magnetic Resonance Imaging]] (MRI), [[electroencephalography]] (EEG). MRI can be used to track brain activity, growth, and connectivity in children,<ref>{{Cite book |title=Magnetic resonance imaging (MRI) |vauthors=Thomason ME |publisher=Cambridge University Press |year=2017 |veditors=Hopkins B, Geangu E, Linkenauger S |edition=2nd |pages=121–128}}</ref> and can track brain development from when a child is a fetus.<ref>{{Cite journal |vauthors=Giedd JN, Raznahan A, Alexander-Bloch A, Schmitt E, Gogtay N, Rapoport JL |date=January 2015 |title=Child psychiatry branch of the National Institute of Mental Health longitudinal structural magnetic resonance imaging study of human brain development |journal=Neuropsychopharmacology |volume=40 |issue=1 |pages=43–49 |doi=10.1038/npp.2014.236 |pmc=4262916 |pmid=25195638}}</ref> EEG can be used to diagnose seizures and encephalopathy, but the conceptual age of the infant must be considered when analyzing the results.<ref>{{Cite book |url=https://www.ncbi.nlm.nih.gov/books/NBK390356/ |title=The Developmental EEG: Premature, Neonatal, Infant, and Children |vauthors=Britton JW, Frey LC, Hopp JL, Korb P, Koubeissi MZ, Lievens WE, Pestana-Knight EM |date=2016 |publisher=American Epilepsy Society |veditors=St Louis EK, Frey LC |language=en |display-authors=6}}</ref>

=== Ethical considerations ===
Most of the [[Medical ethics|ethical challenges]] that exist in studies with adults also exist in studying children, with some notable differences.<ref name="aldridge-2015">{{Cite book |title=Participatory research: Working with vulnerable groups in research and practice |vauthors=Aldridge J |publisher=Bristol University Press |year=2015 |pages=31–64}}</ref><ref>{{Cite conference |date=2018 |title=Ethical Challenges in Researching with Children: An Application Adopting a Mixed Method Approach |conference=Second International Symposium on Qualitative Research (ISQR 2017) |series=Advances in Intelligent Systems and Computing |volume=621 |pages=91–100 |doi=10.1007/978-3-319-61121-1_8 |isbn=978-3-319-61120-4 |vauthors=Barbosa B, Brito PQ |book-title=Computer Supported Qualitative Research}}</ref> Namely [[informed consent]], as while it is important that children consent to participate in research, they cannot give legal consent; parents must give informed consent for their children. Children can informally consent though, and their continued agreement should be reliably checked for by both verbal and nonverbal cues throughout their participation. Also, due to the inherent power structure in most research settings, researchers must consider study designs that protect children from feeling coerced.<ref name="aldridge-2015" />

== Milestones ==
{{See also|Child development stages}}

Milestones are changes in specific physical and mental abilities (such as walking and understanding language) that mark the end of one developmental period and the beginning of another;<ref name="CDC">{{Cite web |date=February 15, 2017 |title=Child Development |url=https://www.cdc.gov/ncbddd/childdevelopment/facts.html |access-date=February 14, 2018 |publisher=[[Centers for Disease Control and Prevention]] (CDC)}}</ref> for stage theories, milestones indicate a stage transition. These milestones, and the chronological age at which they typically occur, have been established via study of when various developmental tasks are accomplished. However, there is considerable variation in when milestones are reached, even between children developing within the typical range. Some milestones are more variable than others; for example, receptive speech indicators do not show much variation among children with typical hearing, but expressive speech milestones can be quite variable.<ref>{{cite journal |last1=Kover |first1=Sara T. |last2=Edmunds |first2=Sarah R. |last3=Ellis Weismer |first3=Susan |title=Brief Report: Ages of Language Milestones as Predictors of Developmental Trajectories in Young Children with Autism Spectrum Disorder |journal=Journal of Autism and Developmental Disorders |date=July 2016 |volume=46 |issue=7 |pages=2501–2507 |doi=10.1007/s10803-016-2756-y |pmid=26936159 |pmc=4903886 }}</ref>

A common concern in child development is [[Global developmental delay|delayed development]] of age-specific developmental milestones. Preventing, and intervening early, in developmental delays is a significant topic in the study of child development. Developmental delays are characterized by comparison with age variability of a milestone, not with respect to average age at achievement.<ref>{{cite book | vauthors = Khan I, Leventhal BL |title=StatPearls |date=2023 |publisher=StatPearls Publishing |url=https://www.ncbi.nlm.nih.gov/books/NBK562231/ |access-date=25 September 2023 |chapter=Developmental Delay|pmid=32965902 }}</ref>

==Physical aspects of development==

===Physical growth===
{{anchor|growth}}

{| class="wikitable center" 
|- 
! colspan=2 | For North American, Indo-Iranian (India, Iran), and European ...
|-
! girls 
! boys 
|- 
|  
*[[Thelarche]] (breast development) 10.5y (8y–13y) 
*[[Pubarche]] (pubic hair) 11y (8.5y–13.5y) 
*Growth spurt 11.25y (10y–12.5y) 
*[[Menarche]] (first menstrual bleeding) 12.5y (10.5y–14.5y) 
*Wisdom tooth eruption 15.5y (14y-17y)
*Adult height reached 15.5y (14y–17y) 
|  
*[[Gonadarche]] (testicular enlargement) 11.5y (9.5y–13.5y) 
*[[Pubarche]] (pubic hair) 12y (10y–14y) 
*Growth spurt 13y (11y–15y) 
*[[Spermarche]] (first ejaculation) 13.5y (11.5y–15.5y) 
*Wisdom tooth eruption 17y (15y-19y)
*Completion of growth 17y (15y–19y) 
|}

Physical growth in [[Human height|stature]] and weight occurs for 15–20 years following birth, as the individual changes from the average weight of {{Convert|3.5|kg|lb|abbr=on}} and length of {{Convert|50|cm|in|abbr=on}} at [[full term]] birth to their final adult size. As stature and weight increase, [[Proportionality (mathematics)|proportion]]s also change, from the relatively large head and small [[torso]] and [[limb (anatomy)|limb]]s of the [[infant|neonate]], to the adult's relatively small head and long torso and limbs.<ref name="tanner">{{Cite book |title=Fetus into Man |vauthors=Tanner JM |publisher=Harvard University Press |year=1990 |isbn=978-0674306929 |location=Cambridge MA}}</ref> In a book directed toward pediatricians it says a child's pattern of growth is in a head-to-toe direction, or cephalocaudal, and in an inward to outward pattern (center of the body to the peripheral) called proximodistal.<ref>{{Cite book |author1=Kristine M. Ruggiero |url=https://books.google.com/books?id=6j7ZDwAAQBAJ&dq=cephalocaudal+and+proximodistal+development+in+children&pg=PA9 |title=Fast Facts Handbook for Pediatric Primary Care: A Guide for Nurse Practitioners and Physician Assistants |author2=Michael Ruggiero |date=2020-09-14 |publisher=Springer Publishing Company |isbn=978-0-8261-5184-1 |language=en}}</ref>

{{multiple image
 | width = 500
 | align = center
 | header = Development from childhood to the end of puberty, from The Adolescent Period
 | image1 = Adolescent Period Average boy 10 to 17 yo.jpg
 | caption1 = Development of a boy from 10 to 17 years old
 | image2 = Adolescent Period Average girl 4 to 16 yo.jpg
 | caption2 =  Development of a girl from 4 to 16 years old
 }}

==== Speed and pattern ====
The speed of physical growth is rapid in the months after birth, then slows, so birth weight is doubled in the first four months, tripled by 1 year, but not quadrupled until 2 years.<ref>{{Cite web | vauthors = Graber EG |title=Physical Growth of Infants and Children - Children's Health Issues |url=https://www.merckmanuals.com/home/children-s-health-issues/growth-and-development/physical-growth-of-infants-and-children |access-date=2020-11-14 |website=Merck Manuals Consumer Version |language=en-US}}</ref> Growth then proceeds at a slow rate until a period of rapid growth occurs shortly before puberty (between
about 9 and 15 years of age).<ref>{{Cite web |title=Puberty Definition, Stages, Duration, Signs for Boys & Girls |url=https://www.medicinenet.com/puberty/article.htm |access-date=2020-11-14 |website=MedicineNet |language=en}}</ref>
Growth is not uniform in rate and timing across all parts of the body. At birth, head size is already relatively near that of an adult, but the lower parts of the body are much smaller than adult size. Thus during development, the head grows relatively little, while the torso and limbs undergo a great deal of growth.<ref name="tanner" />

==== Mechanisms of change ====
Genetic factors play a major role in determining the growth rate, particularly in the characteristic changes in proportions during early human development. However, genetic factors can produce maximum growth only if environmental conditions are adequate, as poor nutrition, frequent injury, or disease can reduce the individual's adult stature; though even the best environment cannot cause growth to a greater stature than is determined by heredity.<ref name="tanner" />

==== Individual variation versus disease ====
Individual differences in height and weight during childhood can be considerable. Some of these differences are due to genetic or environmental factors, but individual differences in reproductive maturation strongly influence development at some points.<ref name="tanner" /> For individuals falling outside these typical variations, the [[Endocrinology#Professional organizations|American Association of Clinical Endocrinologists]] defines [[short stature]] as height more than 2 [[standard deviation]]s below the [[mean (statistics)|mean]] for age and gender, which corresponds to the shortest 2.3% of individuals.<ref name="urlFDA Approves Humatrope for Short Stature">{{Cite web |date=2003-07-25 |title=FDA Approves Humatrope for Short Stature |url=https://www.fda.gov/bbs/topics/ANSWERS/2003/ANS01242.html |url-status=dead |archive-url=https://web.archive.org/web/20050214024746/https://www.fda.gov/bbs/topics/ANSWERS/2003/ANS01242.html |archive-date=February 14, 2005 |access-date=2009-01-13 |publisher=[[U.S. Food and Drug Administration]]}}</ref> In contrast, [[failure to thrive]] is usually defined in terms of [[weight]], and can be evaluated either by a low weight for the child's age, or by a low rate of weight gain.<ref name="urlFailure to Thrive: Miscellaneous Disorders in Infants and Children: Merck Manual Professional">{{Cite web | vauthors = Palumbo EJ |title=Failure to Thrive: Miscellaneous Disorders in Infants and Children | work = Merck Manual Professional | publisher = Merck Sharp & Dohme Corp. |url=http://155.91.16.2/mmpe/sec19/ch286/ch286b.html |url-status=dead |archive-url=https://archive.today/20121129003957/http://155.91.16.2/mmpe/sec19/ch286/ch286b.html |archive-date=2012-11-29 |access-date=2010-03-23 }}</ref> A similar term, [[stunted growth]], generally refers to reduced growth rate as a manifestation of [[malnutrition]] in early childhood.<ref>{{cite web |title=Stunting in a nutshell |url=https://www.who.int/news/item/19-11-2015-stunting-in-a-nutshell |website=www.who.int |access-date=28 September 2023 |language=en}}</ref>

===Motor skills===
[[File:Early toddler.jpg|thumb|right|A child learning to walk]]
Physical abilities change through childhood from the largely reflexive (unlearned, involuntary) movement young infants to the highly skilled voluntary movements characteristic of later childhood and adolescence.

====Definition====
"Motor learning refers to the increasing spatial and temporal accuracy of movements with practice".<ref name="Willingham 1999">{{Cite journal |vauthors=Willingham DB |year=1999 |title=The Neural Basis of Motor-Skill Learning |journal=Current Directions in Psychological Science |volume=8 |issue=6 |pages=178–182 |doi=10.1111/1467-8721.00042 |s2cid=143942008}}</ref>
[[Motor skills]] can be divided into two categories: basic skills necessary for everyday life and recreational skills, including skills for employment or interest based skills.

====Speed and pattern====
The speed of motor development is rapid in early life, as many of the reflexes of the newborn alter or disappear within the first year, and slows later. Like physical growth, motor development shows predictable patterns of cephalocaudal (head to foot) and proximodistal ([[torso]] to extremities) development, with movements at the head and in the more central areas coming under control before those of the lower part of the body or the hands and feet.<ref>{{Cite book | vauthors = Lang D |title=Individual and Family Development, Health, and Well-being |date=August 1, 2022 |publisher=Iowa State University Digital Press|doi=10.31274/isudp.2022.122 }}</ref> Movement ability develops in stage-like sequences,<ref name="Bayley 2005">{{Cite book |title=Bayley Scales of Infant and Toddler Development |vauthors=Bayley N |publisher=Harcourt Assessment |year=2005}}</ref> for example: locomotion at 6–8 months involves creeping on all fours, then proceeds to pulling to stand, "cruising" while holding on to an object, [[walking]] while holding an adult's hand, and finally walking independently.<ref name="Bayley 2005" /> By middle childhood and adolescence, new motor skills are acquired by instruction or observation rather than in a predictable sequence.<ref name="Patterson, 2008" /> There are [[executive functions]] of the brain (working memory, timed inhibition and switching), which are generally considered essential to motor skills, though some{{who|date=June 2024}} argue the reverse dependence—that motor skills are actually precursors to executive function.<ref>{{cite journal |last1=Fathirezaie |first1=Zahra |last2=Matos |first2=Sérgio |last3=Khodadadeh |first3=Elham |last4=Clemente |first4=Filipe Manuel |last5=Badicu |first5=Georgian |last6=Silva |first6=Ana Filipa |last7=Zamani Sani |first7=Seyed Hojjat |last8=Nahravani |first8=Samaneh |title=The Relationship between Executive Functions and Gross Motor Skills in Rural Children Aged 8–10 Years |journal=Healthcare |date=25 March 2022 |volume=10 |issue=4 |pages=616 |doi=10.3390/healthcare10040616 |doi-access=free |pmid=35455794 |pmc=9026807 }}</ref><ref>{{cite journal |last1=Cameron |first1=Claire E. |last2=Brock |first2=Laura L. |last3=Murrah |first3=William M. |last4=Bell |first4=Lindsay H. |last5=Worzalla |first5=Samantha L. |last6=Grissmer |first6=David |last7=Morrison |first7=Frederick J. |title=Fine Motor Skills and Executive Function Both Contribute to Kindergarten Achievement |journal=Child Development |date=July 2012 |volume=83 |issue=4 |pages=1229–1244 |doi=10.1111/j.1467-8624.2012.01768.x |pmid=22537276 |pmc=3399936 |hdl=2027.42/92367 |hdl-access=free }}</ref>

====Mechanisms====
The mechanisms involved in motor development involve some genetic components that determine aspects of muscle and bone strength, as well as the physical size of body parts at a given age. The main areas of the brain involved in motor skills are the [[frontal cortex]], [[parietal cortex]] and [[basal ganglia]]. The [[Prefrontal cortex#Subdivisions|dorsolateral frontal cortex]] is responsible for strategic processing, the parietal cortex is important in controlling perceptual-motor integration and the basal ganglia and supplementary [[motor cortex]] are responsible for motor sequences.<ref>{{cite journal |last1=Hertrich |first1=Ingo |last2=Dietrich |first2=Susanne |last3=Blum |first3=Corinna |last4=Ackermann |first4=Hermann |title=The Role of the Dorsolateral Prefrontal Cortex for Speech and Language Processing |journal=Frontiers in Human Neuroscience |date=17 May 2021 |volume=15 |doi=10.3389/fnhum.2021.645209 |doi-access=free |pmid=34079444 |pmc=8165195 }}</ref><ref>{{cite journal |last1=Ferrandez |first1=A.M |last2=Hugueville |first2=L |last3=Lehéricy |first3=S |last4=Poline |first4=J.B |last5=Marsault |first5=C |last6=Pouthas |first6=V |title=Basal ganglia and supplementary motor area subtend duration perception: an fMRI study |journal=NeuroImage |date=August 2003 |volume=19 |issue=4 |pages=1532–1544 |doi=10.1016/S1053-8119(03)00159-9 |pmid=12948709 }}</ref>

According to a study showing the relationship between coordination and limb growth in infants, genetic components have a huge impact on motor development.<ref name="Piek_2002" /> Intra-limb correlations, like the distance between hip and knee joints, were studied and proved to affect the way an infant will walk. There are also genetic factors like the tendency to use the left or right side of the body more (which allows for early prediction of the dominant hand early). Sample [[Student's t-test|t-tests]] showed that, for female babies, there was a significant difference between the left and right sides at 18 weeks and that the right side was usually dominant.<ref name="Piek_2002" /> Some factors are biological constraints that we cannot control, like male infants tending to have larger and longer arms, yet have an influence on measures like when an infant's reach. Overall, there are both sociological and genetic factors that influence motor development.<ref name="Piek_2002">{{Cite journal |vauthors=Piek JP, Gasson N, Barrett N, Case I |date=December 2002 |title=Limb and gender differences in the development of coordination in early infancy |journal=Human Movement Science |volume=21 |issue=5–6 |pages=621–39 |doi=10.1016/s0167-9457(02)00172-0 |pmid=12620715}}</ref>

Nutrition and exercise also determine strength, flexibility, and the ease and accuracy with which a body part can be moved.<ref name="Patterson, 2008" /><ref>{{Cite web |date=14 June 2011 |title=Flexibility diets |url=http://www.livestrong.com/article/307952-flexibility-diets/ |archive-url=https://web.archive.org/web/20180628072328/http://www.livestrong.com/article/307952-flexibility-diets/ |archive-date=28 June 2018 |website=livestrong.com |vauthors=Bell S}}</ref> It has also been shown that the [[frontal lobe]] develops posterio-anteriorally (from back to front), which is significant in motor development because the hind portion of the frontal lobe is known to control motor functions. This form of development (known as "Proportional Development") explains why motor functions typically develop relatively quickly during childhood, while logic, which is controlled by the middle and front portions of the frontal lobe, usually will not develop until late childhood or early adolescence.<ref name="Soska 2010">{{Cite journal |vauthors=Soska KC, Adolph KE, Johnson SP |date=January 2010 |title=Systems in development: motor skill acquisition facilitates three-dimensional object completion |journal=Developmental Psychology |volume=46 |issue=1 |pages=129–138 |doi=10.1037/a0014618 |pmc=2805173 |pmid=20053012}}</ref> Opportunities to carry out movements help establish the abilities to flex (move toward the trunk) and extend body parts; both capacities are necessary for good motor ability. Skilled voluntary movements such as passing objects from hand to hand develop as a result of practice and learning.<ref name="Patterson, 2008" /> Mastery Climates are autonomy-supportive climates that a teacher can adopt to as a suggested successful learning environment for children to promote and reinforce motor skills by their own motivation. This promotes participation and active learning in children, which [[Piaget's theory of cognitive development]] says is extremely important in early childhood.<ref>{{Cite journal | vauthors = Rudisill ME, Johnson JL |date=2018-07-24 |title=Mastery Motivational Climates in Early Childhood Physical Education: What Have We Learned over the Years? |url=https://www.tandfonline.com/doi/full/10.1080/07303084.2018.1476940 |journal=Journal of Physical Education, Recreation & Dance |language=en |volume=89 |issue=6 |pages=26–32 |doi=10.1080/07303084.2018.1476940 |s2cid=150213725 |issn=0730-3084 |url-access=subscription}}</ref>

====Individual differences====
Individual differences in motor ability are common and depend partly on the child's weight and build. Infants with smaller, slimmer, and more mature builds (proportionally) tend to crawl and crawl earlier than infants with larger builds.<ref name="Piek_2002" /> Infants with more motor experience have been shown to belly crawl and crawl sooner. Not all infants belly crawl; however, those who skip stage this are not as proficient in their ability to crawl on their hands and knees.<ref name="Adolph_1998">{{Cite journal |vauthors=Adolph KE, Vereijken B, Denny MA |date=October 1998 |title=Learning to crawl |journal=Child Development |volume=69 |issue=5 |pages=1299–312 |doi=10.2307/1132267 |jstor=1132267 |pmid=9839417}}</ref> After the infant period, individual differences are strongly affected by opportunities to practice, observe, and be instructed on specific movements. Atypical motor development such as persistent [[primitive reflex]]es beyond 4–6 months, or delayed walking may be an indication of [[Global developmental delay|developmental delays]] or conditions such as [[autism]], [[cerebral palsy]], or [[down syndrome]].<ref name="Patterson, 2008" /> Lower motor coordination results in difficulties with speed accuracy and with trade-off in complex tasks. Encouraging children to participate in activities that cater to their unique personalities is an effective way to help them develop new skills and grow in different environments. Children can learn valuable discipline, dedication, and socialization lessons by challenging themselves to try new things. For example, a naturally shy child may benefit from participating in a drama club, where they can learn to express themselves confidently in front of others. Similarly, a naturally competitive child may thrive in a sports team where they can understand the value of teamwork and sportsmanship. By embracing their individual personalities and interests, children can develop into well-rounded, confident individuals with diverse skills and experiences.
Organized sports can provide a child numerous opportunities to develop essential life skills, such as leadership and teamwork. By being a part of a team, a child can learn the value of working together towards a common goal and understand that individual success is not the sole focus. They can practice thinking beyond themselves and learn the importance of considering the needs of others. Through playing sports, children can develop a strong sense of responsibility, accountability, and respect for their teammates, coaches, and opponents. Overall, organized sports can offer a fun and enriching experience while helping children build character and valuable life skills they can carry into adulthood.
Based on personal experience, working during adolescence provided an opportunity to develop time management skills and accountability. Balancing schoolwork and employment required effective time allocation and punctuality while being responsible enough to communicate with managers regarding school-related conflicts. These essential practices have influenced numerous people in how they are shaped in adulthood.

====Children with disabilities====
Children with [[Down syndrome]] or [[developmental coordination disorder]] are late to reach major motor skills milestones like sucking, grasping, rolling, sitting up and walking, [[developmental verbal dyspraxia|talking]]. Children with Down syndrome sometimes have heart problems, [[Otitis media|frequent ear infections]], [[hypotonia]], or undeveloped muscle mass. Children can also be diagnosed with a [[Learning disabilities|learning disability]], which are disabilities in any of the areas related to language, reading, and mathematics, with basic reading skills being the most common learning disability. The definition of a learning disability focuses on the difference between a child's academic achievement and their apparent capacity to learn.<ref>{{Cite web |title=The Future of Children |url=http://futureofchildren.org/publications/journals/article/index.xml?journalid=57&articleid=340 |url-status=dead |archive-url=https://web.archive.org/web/20160604030230/http://futureofchildren.org/publications/journals/article/index.xml?journalid=57&articleid=340 |archive-date=2016-06-04 |access-date=2016-05-05 |website=futureofchildren.org |publisher=Princeton University}}</ref>

====Population differences====
Regardless of the culture a baby is born into, they are born with a few core domains of knowledge which allow them to make sense of their environment and learn upon previous experience by using motor skills such as grasping or crawling. There are some population differences in motor development, with girls showing some advantages in small muscle usage, including [[articulation (phonetics)|articulation]] of sounds with lips and tongue. Ethnic differences in reflex movements of newborn infants have been reported, suggesting that some biological factor is at work. Cultural differences may encourage learning of motor skills like using the left hand only for sanitary purposes and the right hand for all other uses, producing a population difference.<ref>{{Cite journal |vauthors=Scharoun SM, Bryden PJ |date=2014-02-18 |title=Hand preference, performance abilities, and hand selection in children |journal=Frontiers in Psychology |volume=5 |pages=82 |doi=10.3389/fpsyg.2014.00082 |pmc=3927078 |pmid=24600414 |doi-access=free}}</ref> Cultural factors are play a role in practiced voluntary movements, such as the use of the foot to dribble a soccer ball or the hand to dribble a basketball.<ref name="Patterson, 2008" />

==Mental and emotional aspects of development==
===Cognitive/intellectual===

[[Cognitive development]] is primarily concerned with ways in which young children acquire, develop, and use internal mental capabilities such as [[problem-solving]], [[working memory|memory]], and [[language]].<ref>{{Cite web |title=Cognitive Development Domain - Child Development (CA Dept of Education) |url=https://www.cde.ca.gov/sp/cd/re/itf09cogdev.asp |access-date=2024-01-09 |website=www.cde.ca.gov}}</ref>

====Mechanisms====
[[Cognitive development]] has [[genetics|genetic]] and other biological mechanisms, as is seen in the many genetic causes of [[intellectual disability]]. Environmental factors including food and [[nutrition]], the responsiveness of parents, love, daily experiences, and physical activity can influence early brain development of children.<ref>{{Cite web |date=April 2005 |title=Understanding Brain Development in Young Children |url=http://www.ag.ndsu.edu/pubs/yf/famsci/fs609.pdf |archive-url=https://web.archive.org/web/20141114054024/http://www.ag.ndsu.edu/pubs/yf/famsci/fs609.pdf |archive-date=14 November 2014 |publisher=NDSU Extension Service |vauthors=Brotherson SE |location=Fargo, ND}}</ref> However, although it is assumed that the [[brain]] causes cognition, it is not yet possible to measure specific brain changes and show the cognitive changes they cause. Developmental advances in [[cognition]] are also related to experience and learning, especially for higher-level abilities like abstraction, which depend to a considerable extent on formal education.<ref name="Patterson, 2008" />

====Speed and pattern====
The ability to learn temporal patterns in sequenced actions was investigated in elementary-school-age children. [[temporal logic|Temporal learning]] depends upon a process of integrating timing patterns with action sequences. Children ages 6–13 and young adults performed a serial response time task in which a response and a timing sequence were presented repeatedly in a phase-matched manner, allowing for [[multisensory integration|integrative learning]]. The degree of integrative learning was measured as the slowing in performance that resulted when phase-shifting the sequences. Learning was similar for the children and adults on average but increased with age for the children. Executive function measured by [[Wisconsin Card Sorting Test|Wisconsin Card Sorting Test (WCST)]] performance as well as a measure of response speed also improved with age. Finally, WCST performance and response speed predicted temporal learning. Taken together, the results indicate that temporal learning continues to develop in pre-adolescents and that maturing executive function or processing speed may play an important role in acquiring temporal patterns in sequenced actions and the development of this ability.<ref name="Shin 2011">{{Cite journal |vauthors=Shin JC |date=June 2011 |title=The development of temporal coordination in children |journal=Brain and Cognition |volume=76 |issue=1 |pages=106–114 |doi=10.1016/j.bandc.2011.02.011 |pmid=21463915 |s2cid=20708124}}</ref>{{Primary source inline|date=July 2023|reason=Entire paragraph is a summary of this one study, which may make it a synthesis in violation of WP:NOR}}

====Individual differences====
There are typical individual differences in the ages at which specific cognitive abilities are achieved, but schooling for children in industrialized countries is based on the assumption that there are no large differences.<ref name="Patterson, 2008" /> Delays in cognitive development are problematic for children in cultures that demand advanced cognitive skills for work and for independent living.<ref name="Patterson, 2008" /> Everyday cognitive skills include problem-solving, reasoning, and abstract thinking among many others.<ref>{{Cite web |title=default - Stanford Medicine Children's Health |url=https://www.stanfordchildrens.org/en/topic/default?id=cognitive-development-90-P01594 |access-date=2023-04-13 |website=www.stanfordchildrens.org}}</ref> In the absence of these [[life skills]], children may struggle to complete work in a timely manner or understand certain tasks they are asked to do. If a delay is noticed screenings can possibly find the source of the issue;<ref name="Developmental Delay in Children">{{Cite web |title=Developmental Delay in Children |url=https://my.clevelandclinic.org/health/diseases/14814-developmental-delay-in-children |access-date=2023-04-13 |website=Cleveland Clinic |language=en}}</ref> if there is no underlying issue it is important to help aid the child by reading with them, playing games with them, or reaching out to professionals that can help.'''<ref name="Developmental Delay in Children"/>'''

====Population differences====
There are few population differences in cognitive development: boys and girls show some differences in their skills and preferences, but there is a great deal of overlap between them.<ref name="Patterson, 2008" /> Some differences are seen in fluid reasoning and visual processing, as until about the age of four girls outperform boys in tests of these skills, but by about six or seven boys and girls score similarly. This is also true of [[Intelligence quotient|IQ tests]] where girls tend to outscore boys, but again, as they age the gap lessens.<ref>{{cite journal | vauthors = Buczyłowska D, Ronniger P, Melzer J, Petermann F | title = Sex Similarities and Differences in Intelligence in Children Aged Two to Eight: Analysis of SON-R 2-8 Scores | journal = Journal of Intelligence | volume = 7 | issue = 2 | pages = 11 | date = May 2019 | pmid = 31162390 | pmc = 6630280 | doi = 10.3390/jintelligence7020011 | doi-access = free }}</ref> Differences in cognitive achievement between different ethnic groups appears to result from cultural or other environmental factors.<ref name="Patterson, 2008" />

===Social-emotional===
{{main|Social emotional development}}

====Factor====
Newborn infants do not seem to experience fear or have preferences for contact with any specific people. In the first few months they only experience happiness, sadness, and anger.<ref>{{cite book | vauthors = Gu J, Bourne PE |title=Structural Bioinformatics |date=2009 |publisher=Wiley-Blackwell |location=Hoboken (N.J.) |isbn=978-0-470-18105-8 |edition=2nd}}</ref><ref>{{cite web |title=Infant Emotion: Lifespan Development | work = Open Education Resource |url=https://courses.lumenlearning.com/suny-lifespandevelopment/chapter/infant-emotions/ | publisher = Lumen Learning |access-date=3 October 2023}}</ref> A baby's first smile usually occurs between 6 and 10 weeks, as this usually occurs during social interactions it is called a "social smile".<ref>{{Cite journal |vauthors=Mendes DM, Seidl-de-Moura ML |date=November 2014 |title=Different kinds of infants' smiles in the first six months and contingency to maternal affective behavior |journal=The Spanish Journal of Psychology |volume=17 |pages=E80 |doi=10.1017/sjp.2014.86 |pmid=26055068 |s2cid=39470102}}</ref> By about 8–12 months, they go through a fairly rapid change and become fearful of [[perceived threats]].<ref>{{cite web |title=Emotional and Social Development: 8 to 12 Months |url=https://www.healthychildren.org/English/ages-stages/baby/Pages/Emotional-and-Social-Development-8-12-Months.aspx |website=HealthyChildren.org |date=August 2009 |access-date=28 September 2023 |language=en}}</ref> By around 6–36 months, infants begin to prefer familiar people and show anxiety and distress when separated from them, and when approached by strangers.<ref>{{Cite journal |vauthors=Brooker RJ, Buss KA, Lemery-Chalfant K, Aksan N, Davidson RJ, Goldsmith HH |date=November 2013 |title=The development of stranger fear in infancy and toddlerhood: normative development, individual differences, antecedents, and outcomes |journal=Developmental Science |volume=16 |issue=6 |pages=864–878 |doi=10.1111/desc.12058 |pmc=4129944 |pmid=24118713}}</ref>

Separation anxiety is a typical stage of development to an extent. Kicking, screaming, and throwing temper [[tantrum]]s are normal symptoms of [[separation anxiety]]. The level of intensity of these symptoms can help determine whether or not a child has [[separation anxiety disorder]], which is when a child constantly and intensely refuses to separate from the parent.<ref>{{Cite web |date=2012 |title=Separation Anxiety in Children |url=http://www.helpguide.org/mental/separation_anxiety_causes_prevention_treatment.htm |archive-url=https://web.archive.org/web/20121106003518/http://www.helpguide.org/mental/separation_anxiety_causes_prevention_treatment.htm |archive-date=6 November 2012 |website=helpguide.org |vauthors=Robinson L}}</ref>

The capacity for [[empathy]] and the understanding of social rules begin in the preschool period and continue to develop into adulthood. Middle childhood is characterized by friendships with age-mates, and adolescence by emotions connected with sexuality and the beginnings of romantic love. Anger seems most intense during the toddler and early preschool period, and during adolescence.<ref name="Patterson, 2008" />

====Speed and pattern====
Some aspects of social-emotional development, like empathy, develop gradually, but others, like fearfulness, seem to involve a rather sudden reorganization of the child's experiences of emotion.<ref name="Patterson, 2008" /> Sexual and romantic emotions develop in connection with physical maturation.<ref name="Patterson, 2008" />

====Mechanisms====
Genetic factors appear to regulate some of the social-emotional developments that occur at predictable ages, such as fearfulness and [[Attachment theory|attachment]] to familiar people. Experience plays a role in determining which people are familiar, which [[social rules]] are obeyed, and how anger is expressed.<ref name="Patterson, 2008" />

Parenting practices have been shown to predict children's emotional intelligence. The amount of time mothers spent with their children and the quality of their interactions are important in terms of children's trait emotional intelligence, not only because those times of joint activity reflect a more positive parenting, but because they are likely to promote modeling, reinforcement, shared attention, and social cooperation.<ref>{{Cite journal |vauthors=Alegre A |year=2012 |title=The Relation Between the Time Mothers and Children Spent Together and the Children's Trait Emotional Intelligence |journal=Child & Youth Care Forum |volume=41 |issue=5 |pages=493–508 |doi=10.1007/s10566-012-9180-z |s2cid=144031333}}</ref>

====Population differences====
Population differences may occur in older children, if, for example, they have learned that it is appropriate for boys to express emotion or behave differently than girls, or if customs learned by children of one ethnic group are different than those learned by another.<ref>{{Cite journal |vauthors=Vilhjalmsson R, Kristjansdottir G |date=January 2003 |title=Gender differences in physical activity in older children and adolescents: the central role of organized sport |journal=Social Science & Medicine |volume=56 |issue=2 |pages=363–374 |doi=10.1016/S0277-9536(02)00042-4 |pmid=12473321 |s2cid=30233756}}</ref> Social and emotional differences between boys and girls of the same age may also be associated with the differences in the timing of [[puberty]] seen between the two sexes.<ref name="Patterson, 2008" />

==Development of language and communication==
{{main|Language development}}

===Mechanisms===
Language serves the purpose of communication to express oneself through a systematic and conventional use of sounds, signs, or written symbols.<ref name="hoff2014">Hoff, E. (2014). Language Development. Belmont, CA: Wadsworth Cengage Learning</ref> There are four subcomponents a child must know to acquire language competence: phonology, lexicon, morphology and syntax, and pragmatics.<ref name="E Learn Portal">{{Cite web |title=The Four Language Systems |url=http://www.elearnportal.com/courses/education/methods-of-teaching-language-arts-in-public-schools/methods-of-teaching-language-arts-in-public-schools-four-language-systems |url-status=dead |archive-url=https://web.archive.org/web/20121213063756/http://www.elearnportal.com/courses/education/methods-of-teaching-language-arts-in-public-schools/methods-of-teaching-language-arts-in-public-schools-four-language-systems |archive-date=13 December 2012 |access-date=5 March 2013 |publisher=The Learning House, Inc.}}</ref> These subcomponents combine to form the components of language: [[sociolinguistics]] and [[literacy]].<ref name="hoff2014" /> Currently, there is no single accepted theory of language acquisition but various explanations of language development have been given.

===Components===
The four components of language development include:
* [[Phonology]] is concerned with the sounds of language.<ref>{{Cite book |title=Language acquisition |vauthors=de Villiers JG, de Villiers PA |date=1979 |publisher=Harvard Univ. Press |isbn=978-0-674-50931-3 |edition=3rd |location=Cambridge, Massachusetts |pages=7–16}}</ref> It is the function, behavior, and organization of sounds as linguistic items.<ref>{{Cite book |title=Phonology : an introduction to basic concepts |vauthors=Lass R |date=1984 |publisher=Cambridge University Press |isbn=978-0-521-28183-6 |location=Cambridge |page=1}}</ref> Phonology considers what the sounds of language are and what the rules are for combining sounds. Phonological acquisition in children can be measured by frequency and accuracy of production of various vowels and consonants, the acquisition of phonemic contrasts and distinctive features, or by viewing development in regular stages and to characterizing systematic strategies they adopt.<ref>{{Cite book |title=Language acquisition |vauthors=de Villiers JG, de Villiers PA |date=1979 |publisher=Harvard Univ. Press |isbn=978-0-674-50931-3 |edition=3rd |location=Cambridge, Massachusetts |pages=42–43}}</ref> 
* [[Lexicon]] is similar to vocabulary as they both describe the complex dictionary of words used in speech production and comprehension.<ref>{{Cite book |title=Introduction to English linguistics |vauthors=Plag I, Braun M, Lappe S, Schramm M |date=2007 |publisher=Mouton de Gruyter |isbn=978-3-11-018969-8 |edition=1st |location=Berlin |page=150}}</ref> The lexicon of a language also includes that language's [[morpheme]]s. Morphemes act as minimal meaning-bearing elements or building blocks of something in language that makes sense. For example, in the word "cat", the component "cat" makes sense as does "at", but "at" does not mean the same thing as "cat". In this example, "ca" does not mean anything. 
* [[Morphology (linguistics)|Morphology]] is the study of words and how they are formed. Morphology is also the branch of linguistics that deals with words, their internal structure and how they are formed. It is also the mental system involved in word formation.<ref>{{Cite book |title=What is Morphology |vauthors=Aronoff M, Fudeman K |date=2011 |publisher=John Wiley & Sons |edition=2nd}}</ref>
* [[Pragmatics]] is the study of the relationship between linguistic forms and speakers of the language,<ref>{{Cite book |title=What is the matter with communicative competence? : an analysis to encourage teachers of English to assess the very basis of their teaching |vauthors=Peterwagner R |date=2005 |publisher=Lit-Verl. |isbn=978-3825884871 |location=Münster |page=24}}</ref> it also incorporates how speech is used to serve different functions. Pragmatics can be defined as the ability to communicate one's feelings and desires to others.<ref>{{Cite book |title=Language acquisition |vauthors=de Villiers JG, de Villiers PA |date=1979 |publisher=Harvard Univ. Press |isbn=978-0-674-50931-3 |edition=3rd |location=Cambridge, Massachusetts |page=229}}</ref>

Children's development of language also includes [[semantics]] which is the attachment of meaning to words. This happens in three stages. First, each word means an entire sentence. For example, a young child may say "mama" but the child may mean "Here is Mama", "Where is Mama?", or "I see Mama." In the second stage, words have meaning but do not have complete definitions. This stage occurs around age two or three. Third, around age seven or eight, words have adult-like definitions and their meanings are more complete.<ref name="hopper1973">{{Cite book |title=Children's Speech |vauthors=Hopper R, Naremore RC |date=1973 |publisher=Harper & Row |location=New York, NY}}</ref>

A child learns the [[syntax]] of their language when they are able to join words together into sentences and understand multiple-word sentences said by other people. There appear to be six major stages in which a child's acquisition of syntax develops.<ref name="wood1976" /> First, is the use of sentence-like words in which the child communicates using one word with additional vocal and bodily cues. This stage usually occurs between 12 and 18 months of age. Second, between 18 months to two years, there is the modification stage where children communicate concepts by modifying a topic word. The third stage, between two and three years old, involves the child using complete subject-predicate structures to communicate concepts. Fourth, children make changes on basic sentence structure that enables them to communicate more complex concepts. This stage occurs between the ages of two and a half years to four years. The fifth stage of categorization involves children aged three and a half to seven years refining their sentences with more purposeful word choice that reflects their complex system of categorizing word types. Finally, children use structures of language that involve more complicated syntactic relationships between the ages of five years old to ten years old.<ref name="wood1976">{{Cite book |title=Children and communication: verbal and nonverbal language development |vauthors=Wood BS |date=1976 |publisher=Prentice-Hall |location=Englewood Cliffs, N.J.}}</ref>
<!-- Deleted image removed: [[File:Unanswered Letter to Osama by Daniel Geery 5-5-2011.jpg|thumb|right|young children in communication with one another]] -->

===Sequential skills and milestones===
{| class="wikitable"
|+ Sequential skills in learning to talk<ref>{{Cite book |title=Developmental Change. The Social World of Children Learning to Talk |vauthors=Hart B, Risley TR |date=1999 |publisher=P.H. Brookes Pub. |location=Baltimore, Md. |page=271}}</ref>
|-
! Child Age in Months !! Language Skill
|-
| 0–3 || Vocal play: cry, coo, gurgle, grunt
|-
| 3+ || Babble: undifferentiated sounds
|-
| 6–10 || Babble: canonical/reduplicated syllables
|-
| 9+ || Imitation
|-
| 8–18 || First words
|-
| 13–15|| Expressive jargon, intonational sentences
|-
| 13–19 || 10-word vocabulary 
|-
| 14–24 || 50-word vocabulary
|-
| 13–27|| Single-word stage and a few sentences; 2–3 word combinations; Articles: a/the; Plural: -s
|-
| 23–24 || Irregular past: went, modal and verb: can/will; 28 to 436-word vocabulary; 93–265 utterances per hour
|-
| 25–27 || Regular past: -ed; Auxiliary "be": -'m, -'s
|-
| 23–26 || Third-person singular: -s; 896 to 1,507-word vocabulary; 1,500 to 1,700 words per hour
|}

Infants begin with cooing and soft vowel sounds. Shortly after birth, this system is developed as the infants begin to understand that their noises, or non-verbal communication, lead to a response from their caregiver.<ref name="Hart and Risley">{{Cite book |title=The Social World of Children Learning to Talk |vauthors=Hart B |date=1999 |publisher=P.H. Brookes Pub |isbn=978-1-55766-420-4 |location=Baltimore, Md. |pages=53–72}}</ref> This will then progress into babbling around 5 months of age, with infants first babbling consonant and vowel sounds together that may sound like "ma" or "da".<ref name="woolfolk2012">{{Cite book |title=Child and adolescent development |vauthors=Woolfolk A, Perry NE |date=2012 |publisher=Pearson Education |isbn=978-1-292-04106-3 |location=Upper Saddle River, NJ}}</ref> At around 8 months of age, babbling increases to include repetition of sounds, such as "ma-ma" and "da-da". Around this age infants also learn the forms for words and which sounds are more likely to follow other sounds.<ref name="woolfolk2012" /> At this stage, much of the child's communication is open to interpretation. For example, if a child says "bah" when they are in a toy room with their guardian, it is likely to be interpreted as "ball" because the toy is in sight. However, if you were to listen to the same 'word' on a recorded tape without knowing the context, one might not be able to figure out what the child was trying to say.<ref name="Hart and Risley" />

A child's [[receptive language]], the understanding of others' [[speech]], has a gradual development beginning at about 6 months.<ref name="pal2011">{{Cite book |title=Education Psychology |vauthors=Pal BK |date=2011 |publisher=Prerna Parkashan |location=Delhi}}</ref> However, [[expressive language]], the production of words, moves rapidly after its beginning at about a year of age, with a "vocabulary explosion" of rapid word acquisition occurring in the middle of the second year.<ref name="pal2011" /> Grammatical rules and word combinations appear at about age two.<ref name="pal2011" /> Between 20 and 28 months, children move from understanding the difference between high and low, hot and cold and begin to change "no" to "wait a minute", "not now" and "why". Eventually, they are able to add pronouns to words and combine them to form short sentences.<ref name="Hart and Risley" /> Mastery of vocabulary and [[grammar]] continue gradually through the preschool and school years, with adolescents having smaller vocabularies than adults and experiencing more difficulty with constructions such as the passive voice.<ref name="pal2011" />

By age 1, children are able to say 1–2 words, respond to their name, imitate familiar sounds and follow simple instructions.<ref name="woolfolk2012" /> Between 1–2 years old, the child uses 5–20 words, says 2-word sentences, expresses their wishes by saying words like "more" or "up", and understands the word "no".<ref name="woolfolk2012" /> Between 2 and 3 years of age, the child is able to refer to themself as "me", combine nouns and verbs, use short sentences, use some simple plurals, answer "where" questions, and has a vocabulary of about 450 words.<ref name="woolfolk2012" /> By age 4, children are able to use sentences of 4–5 words and have a vocabulary of about 1000 words.<ref name="woolfolk2012" /> Children between the ages of 4 and 5 years old are able to use past tense, have a vocabulary of about 1,500 words, and ask questions like "why?" and "who?".<ref name="woolfolk2012" /> By age 6, the child has a vocabulary of 2,600 words, is able to form sentences of 5–6 words and use a variety of different types of sentences.<ref name="woolfolk2012" /> By the age of 5 or 6 years old, the majority of children have mastered the basics of their native language.<ref name="woolfolk2012" />

Infants, up to 15 month-olds, are initially unable to understand familiar words in their native language pronounced using an unfamiliar accent.<ref name="apa.org">{{Cite journal |vauthors=van Heugten M, Johnson EK |date=February 2014 |title=Learning to contend with accents in infancy: benefits of brief speaker exposure |journal=Journal of Experimental Psychology. General |volume=143 |issue=1 |pages=340–350 |doi=10.1037/a0032192 |pmid=23506084}}</ref> This means that a Canadian-English speaking infant cannot recognize familiar words pronounced with an Australian-English accent. This skill develops close to their second birthday.<ref name="apa.org" /> However, this can be overcome when a highly familiar story is read in the new accent prior to the test, suggesting the essential functions of underlying spoken language is in place earlier than previously thought.<ref name="apa.org" />

Vocabulary typically grows from about 20 words at 18 months to around 200 words at 21 months. Starting around 18 months the child begins to combine words into two-word sentences, which the adult typically expands to clarify its meaning. By 24–27 months the child is producing three or four-word sentences using a logical, if not strictly correct, syntax.<ref name="pal2011" />  The theory is that children apply a basic set of rules such as adding 's' for plurals or inventing simpler words out of words too complicated to repeat like "choskit" for [[chocolate biscuit]].<ref name="pal2011" />  Following this there is a rapid appearance of grammatical rules and ordering of sentences.<ref name="pal2011" /> There is often an interest in [[rhyme]], and imaginative play frequently includes conversations. Children's recorded monologues give insight into the development of the process of organizing information into meaningful units.<ref name="pal2011" />

By age three the child begins to use complex sentences, including relative clauses, although they are still perfecting various [[linguistic]] systems. By five years of age the child's use of language is very similar to that of an adult. From the age of about three children can indicate fantasy or make-believe linguistics, produce coherent personal stories and fictional narratives with beginnings and endings.<ref name="pal2011" /> It is argued that children devise narrative as a way of understanding their own experience and as a medium for communicating their meaning to others.<ref name="pal2011" />

The ability to engage in extended discourse emerges over time from regular conversation with adults and peers. For this, a child needs to learn to combine their perspective with that of others and with outside events and learn to use linguistic indicators to show they are doing this. They also learn to adjust their language depending on who they are speaking to.<ref name="pal2011" /> Typically by the age of about 9 a child can recount other narratives in addition to their own experiences, from the perspectives of the author, the characters in the story and their own views.<ref name="pal2011" />

===Theories===
Although the role of adult speech is important in facilitating the child's learning, there is considerable disagreement among theorists about the extent to which it influences children's early meanings and expressive words. Findings about the initial mapping of new words, the ability to decontextualize words, and refine meaning of words are diverse.<ref name="Smith, Cowie, Blades, 2011" /> One hypothesis, known as the syntactic [[bootstrapping]] hypothesis, refers to the child's ability to infer meaning from cues by using grammatical information from the structure of sentences.<ref name="gleitman">{{Cite journal |vauthors=Gleitman LR |year=1990 |title=The structural sources of verb meaning |journal=Language Acquisition |volume=1 |issue=1 |pages=3–55 |doi=10.1207/s15327817la0101_2 |s2cid=144713838}}</ref>

Another theory is the multi-route model which argues that context-bound words and referential words follow different routes; the first being mapped onto event representations and the latter onto mental representations. In this model, parental input has a critical role but the children ultimately rely on cognitive processing to establish subsequent use of words.<ref name="Barrett">{{Cite journal |vauthors=Barrett M, Harris M, Chasin J |date=February 1991 |title=Early lexical development and maternal speech: a comparison of children's initial and subsequent uses of words |journal=Journal of Child Language |volume=18 |issue=1 |pages=21–40 |doi=10.1017/S0305000900013271 |pmid=2010501 |s2cid=35724493}}</ref> However, naturalistic research on language development has indicated that preschoolers' vocabularies are strongly associated with the number of words said to them by adults.<ref name="hartris">{{Cite book |title=Meaningful Differences in the Everyday Experience of Young American Children |vauthors=Hart B, Risley TR |date=1995 |publisher=P.H. Brookes |isbn=978-1-55766-197-5}}{{page needed|date=August 2022}}</ref>

There is no single accepted theory of language acquisition. Instead, there are current theories that help to explain theories of language, theories of cognition, and theories of development. They include the generativist theory, [[social interactionist theory]], usage-based theory ([[Michael Tomasello|Tomasello]]), connectionist theory, and behaviorist theory ([[B. F. Skinner|Skinner]]). Generativist theories say that [[universal grammar]] is innate and language experience activates that innate knowledge.<ref name="hoff2009">{{Cite book |title=Language development |vauthors=Hoff E |date=2009 |publisher=Wadsworth Cengage Learning |isbn=978-0-495-50820-5}}{{page needed|date=August 2022}}</ref> Social interactionist theories define language as a social phenomenon where children acquire language because they want to communicate with others; this theory is heavily based on social-cognitive abilities that drive the language acquisition process.<ref name="hoff2009" /> Usage-based theories define language as a set of formulas that emerge from the child's learning abilities in correlation with their social cognitive interpretation and their understanding of the speakers' intended meanings.<ref name="hoff2009" /> Connectionist theory is a pattern-learning procedure that defines language as a system composed of smaller subsystems or patterns of sound or meaning.<ref name="hoff2009" /> Behaviorist theories defined language as the establishment of [[positive reinforcement]], but are now regarded as only being of historical interest.<ref name="hoff2009" />

===Communication===
[[Communication]] can be defined as the exchange and negotiation of information between two or more individuals through verbal and nonverbal symbols, oral and written (or visual) modes, and the production and comprehension processes of communication.<ref name="richards1986">{{Cite book |title=Language and Communication |date=1986 |publisher=Longman Group Limited |veditors=Richards JC, Schmidt WR |location=USA}}</ref> According to First International Congress for the Study of Child Language, "the general hypothesis [is that] access to social interaction is a prerequisite to normal language acquisition".<ref name="Dale and Snow">{{Cite book |title=Child language, an international perspective: selected papers from the First International Congress for the Study of Child Language |vauthors=Dale PS, Ingram D, Snow CE |date=1981 |publisher=University Park Press |isbn=978-0-8391-1608-0 |location=Baltimore, Md. |pages=195–214 |chapter=Social Interaction and Language Acquisition.}}</ref> Principles of conversation include two or more people focusing on one topic. All questions in a conversation should be answered, comments should be understood or acknowledged and any directions should, in theory, be followed. In the case of young children these conversations are expected to be basic or redundant. The role of a guardians during developing stages is to convey that conversation is meant to have a purpose, as well as teaching children to recognize the other speaker's emotions.<ref name="Dale and Snow" />

Communicative language is both [[Verbal communication|verbal]] and [[Nonverbal communication|nonverbal]], and to achieve communication competence, four components must be mastered. These components are: grammatical competence, including vocabulary knowledge, rules of word sentence formation, etc.; sociolinguistic competence, or the appropriate meanings and grammatical forms in different social contexts; discourse competence, which is having the knowledge required to combine forms and meanings; and strategic competence in the form of knowledge about verbal and nonverbal communication strategies.<ref name="richards1986" /> The attainment of [[communicative competence]] is an essential part of actual communication.<ref>{{Cite journal |vauthors=Burgoon KJ, Le Poire AB |year=1993 |title=Effects of Communication Expectancies, Actual Communication, and Expectancy Disconfirmation on Evaluations of Communicators and Their Communication Behavior |journal=Human Communication Research |volume=20 |pages=67–96 |doi=10.1111/j.1468-2958.1993.tb00316.x|doi-access=free }}</ref>

Language development is viewed as a motive to communication, and the communicative function of language in-turn provides the motive for language development. Jean Piaget uses the term "acted conversations" to explain a child's style of communication that relies more heavily on [[gesture]]s and body movements than words.<ref name="wood1976" /> Younger children depend on gestures for a direct statement of their message. As they begin to acquire more language, body movements take on a different role and begin to complement the verbal message.<ref name="wood1976" /> These nonverbal bodily movements allow children to express their emotions before they can express them verbally. The child's nonverbal communication of how they are feeling is seen in babies 0 to 3 months who use wild, jerky movements of the body to show excitement or distress.<ref name="wood1976" /> This develops to more rhythmic movements of the entire body at 3 to 5 months to demonstrate the child's anger or delight.<ref name="wood1976" /> Between 9–12 months of age, children view themselves as joining the communicative world.<ref name="hoff2014" />

Before 9–12 months, babies interact with objects and interact with people, but they do not interact with people about objects. This developmental change is the change from primary [[intersubjectivity]] (capacity to share oneself with others) to secondary intersubjectivity (capacity to share one's experience), which changes the infant from an unsociable to socially engaging creature.<ref name="hoff2014" /> Around 12 months of age the use of communicative gestures begins, including communicative pointing where an infant points to request something, or to point to provide information.<ref name="hoff2014" /> Another communicative gesture presents around the age of 10 and 11 months where infants start gaze-following, by looking where another person is looking.<ref name="hoff2014" /> This [[joint attention]] results in changes to their social cognitive skills between the ages of 9 and 15 months as their time is increasingly spent with others.<ref name="hoff2014" /> Children's use of non-verbal communicative gestures predicts future language development. The use of non-verbal communication in the form of gestures indicate the child's interest in communication development, and the meanings they choose to convey that are soon revealed through the verbalization of language.<ref name="hoff2014" />

Language acquisition and development contribute to the verbal form of communication. Children originate with a linguistic system where the words they learn are the words used for functional meaning.<ref name="hoff2009" /> This instigation of speech has been termed pragmatic [[bootstrapping (linguistics)|bootstrapping]]. According to this theory children view words as a means of social connection, in that words are used to connect the communicative intentions of the speaker to new words.<ref name="hoff2009" /> Hence, the competence of verbal communication through language is achieved by gains in [[syntax]] or [[grammar]].

Another function of communicating through language is related to pragmatic development.<ref>{{Cite book |title=Essays in Developmental Science. |vauthors=Ninio A, Snow EC |date=1996 |publisher=Westview Press |location=Boulder, CO, US}}</ref> Pragmatic development includes the child's intentions of communication before they knows how to express these intentions, and throughout the first few years of life both language and communicative functions develop.<ref name="hoff2009" />

When children acquire language and learn to use language for communicative functions ([[pragmatics]]), children also gain knowledge about how to participate in conversations and how to relay past experiences/events ([[discourse |discourse knowledge]]), as well as learning how to use language appropriately for their social situation or social group ([[Sociolinguistics|sociolinguistic knowledge]]).<ref name="hoff2009" />

Within the first two years of life, a child's language ability progresses and conversational skills, such as the mechanics of verbal interaction, develop. Mechanics of verbal interaction include taking turns, initiating topics, repairing [[miscommunication]], and responding to lengthen or sustain the conversation.<ref name="hoff2009" />

Conversation is asymmetrical when a child interacts with an adult because the adult is the one to create structure in the conversation, and to build upon the child's contributions. In accordance to the child's developing conversational skills, asymmetrical conversation between adult and child advance to an equal [[temperament]] of conversation. This shift in balance of conversation suggests a development of [[narrative discourse]] in communication.<ref name="hoff2009" /> Ordinarily, the development of communicative competence and the development of language are linked to one another.<ref name="hoff2009" />

===Causes of delays===
{{unreferenced section|date=July 2023}}

====Individual differences====
Delays in language skills are the most frequent type of developmental delay. According to demographics 1 out of 6 children have a significant language delay;<ref>{{cite journal | vauthors = Sansavini A, Favilla ME, Guasti MT, Marini A, Millepiedi S, Di Martino MV, Vecchi S, Battajon N, Bertolo L, Capirci O, Carretti B, Colatei MP, Frioni C, Marotta L, Massa S, Michelazzo L, Pecini C, Piazzalunga S, Pieretti M, Rinaldi P, Salvadorini R, Termine C, Zuccarini M, D'Amico S, De Cagno AG, Levorato MC, Rossetto T, Lorusso ML | display-authors = 6 | title = Developmental Language Disorder: Early Predictors, Age for the Diagnosis, and Diagnostic Tools. A Scoping Review | journal = Brain Sciences | volume = 11 | issue = 5 | pages = 654 | date = May 2021 | pmid = 34067874 | pmc = 8156743 | doi = 10.3390/brainsci11050654 | doi-access = free }}</ref> [[Speech delay|speech]]/[[language delay]] is three to four times more common in boys than in girls.<ref>{{cite journal | vauthors = Leung AK, Kao CP | title = Evaluation and management of the child with speech delay | language = en-US | journal = American Family Physician | volume = 59 | issue = 11 | pages = 3121–8, 3135 | date = June 1999 | pmid = 10392594 | url = https://www.aafp.org/pubs/afp/issues/1999/0601/p3121.html }}</ref> Some children also display behavioral problems due to their frustration of not being able to express what they want or need.<ref name="McLaughlin_2011">{{cite journal | vauthors = McLaughlin MR | title = Speech and language delay in children | language = en-US | journal = American Family Physician | volume = 83 | issue = 10 | pages = 1183–1188 | date = May 2011 | pmid = 21568252 | url = https://www.aafp.org/pubs/afp/issues/2011/0515/p1183.html }}</ref>

Simple speech delays are usually temporary. Most cases are solved on their own or with a little extra attention from the family. It is the parent's duty to encourage their baby to talk to them with gestures or sounds and for them to spend a great amount of time playing with, reading to, and communicating with their baby. In certain circumstances, parents will have to seek professional help, such as a [[Speech-language pathology|speech therapist]].<ref name="McLaughlin_2011" />

It is important to take into consideration that sometimes delays can be a warning sign of more serious conditions that could include [[auditory processing disorder]]s, [[hearing loss]], [[developmental verbal dyspraxia]], developmental delay in other areas, or an autism spectrum disorder (ASD).<ref name="McLaughlin_2011" />

====Environmental causes====
There are many environmental causes that are linked to language delays, including situations where the child  has their full attention on another skill, such as walking. The child may have a twin or a sibling close to their own age and may not be receiving the parent's full attention. Another possibility is that the child is in a daycare with too few adults to administer individual attention. General development can be impacted if the child does not receive an adequately nutritional diet.<ref>{{Cite journal |last1=Stanek |first1=Kaye |last2=Abbott |first2=Douglas |last3=Cramer |first3=Sheran |date=November 1990 |title=Diet quality and the eating environment of preschool children |url=http://dx.doi.org/10.1016/s0002-8223(21)01844-7 |journal=Journal of the American Dietetic Association |volume=90 |issue=11 |pages=1582–1584 |doi=10.1016/s0002-8223(21)01844-7 |pmid=2229855 |issn=0002-8223|url-access=subscription }}</ref> Perhaps the most obvious environmental cause would be a child that suffers from psychosocial deprivation such as poverty, poor housing, neglect, inadequate linguistic stimulation, or emotional stress.<ref>{{cite journal | vauthors = Sunderajan T, Kanhere SV | title = Speech and language delay in children: Prevalence and risk factors | journal = Journal of Family Medicine and Primary Care | volume = 8 | issue = 5 | pages = 1642–1646 | date = May 2019 | pmid = 31198730 | pmc = 6559061 | doi = 10.4103/jfmpc.jfmpc_162_19 | doi-access = free }}</ref>

====Neurological causes====
Language delay can be caused by a substantial number of underlying disorders, such as [[intellectual disability]], which accounts for more than 50 percent of language delays. Language delay is usually more severe than other developmental delays in intellectually disabled children, and it is usually the first obvious symptom of intellectual disability. Intellectual disability causes global language delay, including delayed auditory comprehension and delayed use of gestures.<ref>{{cite journal | vauthors = Marrus N, Hall L | title = Intellectual Disability and Language Disorder | journal = Child and Adolescent Psychiatric Clinics of North America | volume = 26 | issue = 3 | pages = 539–554 | date = July 2017 | pmid = 28577608 | pmc = 5801738 | doi = 10.1016/j.chc.2017.03.001 }}</ref>

Impaired hearing is another of the most common causes of language delay. A child who can not hear or process speech in a clear and consistent manner will have a [[language delay]], and even the most minimum [[hearing impairment]] or [[auditory processing disorder|auditory processing deficit]] can considerably affect language development. Generally the more the severe the impairment, the more serious the language delay.<ref>{{cite journal | vauthors = Lang-Roth R | title = Hearing impairment and language delay in infants: Diagnostics and genetics | journal = GMS Current Topics in Otorhinolaryngology, Head and Neck Surgery | volume = 13 | pages = Doc05 | date = 2014-12-01 | pmid = 25587365 | pmc = 4273166 | doi = 10.3205/cto000108 }}</ref> Nonetheless, [[deaf]] children that are born to families who use [[sign language]] develop infant babble and use a fully expressive sign language at the same pace as hearing children.<ref>{{cite journal | vauthors = Caselli N, Pyers J, Lieberman AM | title = Deaf Children of Hearing Parents Have Age-Level Vocabulary Growth When Exposed to American Sign Language by 6 Months of Age | journal = The Journal of Pediatrics | volume = 232 | pages = 229–236 | date = May 2021 | pmid = 33482219 | pmc = 8085057 | doi = 10.1016/j.jpeds.2021.01.029 }}</ref>

[[Dyslexia|Developmental Dyslexia]] is a developmental reading disorder that occurs when the brain does not properly recognize and process the graphic symbols that represent the sounds of speech. Children with dyslexia may encounter problems in rhyming and separating the sounds that compose words, which is essential in learning to read as early [[Reading (process)|reading]] skills rely heavily on word recognition. When using an [[alphabet]] [[writing system]] this involves in having the ability to separate out the sounds in words and be able to match them with letter and groups of letters. Difficulty connecting the sounds of language to the letters of words may result difficulty in understanding sentences. Confusion between similar letters, such as "b" and "d" can occur. In general the symptoms of dyslexia are: difficulty in determining the meaning of a simple sentence, learning to recognize written words, and difficulty in rhyming.

[[Autism]] and speech delay are usually correlated. Problems with verbal language is the most common sign of autism. Early diagnosis and treatment of autism can significantly help the child improve their speech skills. Autism is recognized as one of the five pervasive developmental disorders, distinguished by problems with language, speech, communication and social skills that present in early childhood. Some common types of language disorders are having limited to no verbal speech, [[echolalia]] or repeating words out of context, problems responding to verbal instruction and ignoring people who speak to them directly.<ref>{{cite journal | vauthors = Vogindroukas I, Stankova M, Chelas EN, Proedrou A | title = Language and Speech Characteristics in Autism | journal = Neuropsychiatric Disease and Treatment | volume = 18 | pages = 2367–2377 | date = 2022-10-14 | pmid = 36268264 | pmc = 9578461 | doi = 10.2147/NDT.S331987 | doi-access = free }}</ref>

==Other aspects of development==
=== Gender ===
{{Main|Gender identity}}

[[Gender identity]] involves how a person perceives themselves as male, female, or a variation of the two. Children can identify themselves as belonging to a certain gender as early as two years old,<ref>{{Cite journal |vauthors=Halim ML |date=2016-03-29 |title=Princesses and Superheroes: Social-Cognitive Influences on Early Gender Rigidity |journal=Child Development Perspectives |language=en |volume=10 |issue=3 |pages=155–160 |doi=10.1111/cdep.12176 |issn=1750-8592}}</ref> but how gender identity is developed is a topic of scientific debate. Several factors are involved in determining an individual's gender, including neonatal hormones, postnatal socialization, and genetic influences.<ref name="steensma-2013">{{Cite journal |vauthors=Steensma TD, Kreukels BP, de Vries AL, Cohen-Kettenis PT |date=July 2013 |title=Gender identity development in adolescence |journal=Hormones and Behavior |volume=64 |issue=2 |pages=288–297 |doi=10.1016/j.yhbeh.2013.02.020 |pmid=23998673 |s2cid=23056757}}</ref> Some believe that gender is malleable until late childhood,<ref name="steensma-2013" /> while others argue that gender is established early and gender-typed socialization patterns either reinforce or soften the individual's notion of gender.<ref name="maccoby-2000">{{Cite journal |vauthors=Maccoby EE |date=2000-12-02 |title=Perspectives on gender development |journal=International Journal of Behavioral Development |language=en |volume=24 |issue=4 |pages=398–406 |doi=10.1080/016502500750037946 |issn=0165-0254 |s2cid=143918530}}</ref> Since most people identify as the gender that is typically associated to their genitalia, studying the impact of these factors is difficult.

Evidence suggests that [[Androgen|neonatal androgens]], male sex hormones produced in the womb during gestation, play an important role. [[Testosterone]] in the womb directly codes the brain for either male or female-typical development. This includes both the physical structure of the brain and the characteristics the person expresses because of it. People exposed to high levels of testosterone during gestation typically develop a male gender identity, while those not exposed to testosterone, or who lack the receptors necessary to interact with it, typically develop a female gender identity.<ref name="steensma-2013" /><ref name="roselli-2018">{{Cite journal |vauthors=Roselli CE |date=July 2018 |title=Neurobiology of gender identity and sexual orientation |journal=Journal of Neuroendocrinology |volume=30 |issue=7 |pages=e12562 |doi=10.1111/jne.12562 |pmc=6677266 |pmid=29211317}}</ref>

An individual's genes are also thought to interact with the hormones during gestation and, in turn, affect gender identity, but the genes responsible for this and their effects have not been precisely documented and evidence is limited.<ref name="roselli-2018" /> It is unknown whether socialization plays a part in determining gender identity postnatally. It is well documented that children actively seek out information on how to properly interact with others based on their gender,<ref name="maccoby-2000" /> but the extent to which these role models, which can include parents, friends, and TV characters, influence gender identity is less clear and no consensus has been reached.

===Race===
In addition to the course of development, previous literature has looked at how race, ethnicity, and socioeconomic status has affected child development. Some studies seem to speak to the importance of adult supervision of adolescent youth.<ref>{{cite journal | vauthors = Quintana SM, Aboud FE, Chao RK, Contreras-Grau J, Cross WE, Hudley C, Hughes D, Liben LS, Nelson-Le Gall S, Vietze DL | display-authors = 6 | title = Race, ethnicity, and culture in child development: contemporary research and future directions | journal = Child Development | volume = 77 | issue = 5 | pages = 1129–1141 | date = 2006 | pmid = 16999787 | doi = 10.1111/j.1467-8624.2006.00951.x | url = https://srcd.onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8624.2006.00951.x | url-status = dead | access-date = 2020-10-18 | archive-url = https://web.archive.org/web/20220308163216/https://srcd.onlinelibrary.wiley.com/doi/abs/10.1111/j.1467-8624.2006.00951.x | archive-date = 2022-03-08 | url-access = subscription }}</ref> Literature suggested that African American child development was sometimes differentiated between cultural socialization and racial socialization.<ref>{{cite journal |last1=Saleem |first1=Farzana T. |last2=English |first2=Devin |last3=Busby |first3=Danielle R. |last4=Lambert |first4=Sharon F. |last5=Harrison |first5=Aubrey |last6=Stock |first6=Michelle L. |last7=Gibbons |first7=Frederick X. |title=The Impact of African American Parents' Racial Discrimination Experiences and Perceived Neighborhood Cohesion on their Racial Socialization Practices |journal=Journal of Youth and Adolescence |date=July 2016 |volume=45 |issue=7 |pages=1338–1349 |doi=10.1007/s10964-016-0499-x |pmid=27189721 |pmc=5192560 }}</ref><ref>{{cite journal |last1=Tang |first1=Sandra |last2=McLoyd |first2=Vonnie C. |last3=Hallman |first3=Samantha K. |title=Racial Socialization, Racial Identity, and Academic Attitudes Among African American Adolescents: Examining the Moderating Influence of Parent–Adolescent Communication |journal=Journal of Youth and Adolescence |date=June 2016 |volume=45 |issue=6 |pages=1141–1155 |doi=10.1007/s10964-015-0351-8 |pmid=26369349 |pmc=5407464 }}</ref> Further, a different study found that most immigrant youth choose majors focusing on the fields of science and math.<ref>{{cite journal | vauthors = Rangel MA, Shi Y | title = Early patterns of skill acquisition and immigrants' specialization in STEM careers | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 116 | issue = 2 | pages = 484–489 | date = January 2019 | pmid = 30598440 | pmc = 6329961 | doi = 10.1073/pnas.1812041116 | doi-access = free | bibcode = 2019PNAS..116..484R }}</ref>

== Risk factors ==
Risk factors in child development include: malnutrition, maternal depression, maternal substance use and pain in infancy; though many more factors have been studied.<ref name="Mora">{{Cite journal |vauthors=Mora JO, Herrera MG, Suescun J, de Navarro L, Wagner M |date=September 1981 |title=The effects of nutritional supplementation on physical growth of children at risk of malnutrition |journal=The American Journal of Clinical Nutrition |volume=34 |issue=9 |pages=1885–1892 |doi=10.1093/ajcn/34.9.1885 |pmid=7282613}}</ref><ref name="Kurstjens">{{Cite journal |vauthors=Kurstjens S, Wolke D |date=July 2001 |title=Effects of maternal depression on cognitive development of children over the first 7 years of life |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=42 |issue=5 |pages=623–636 |doi=10.1111/1469-7610.00758 |pmid=11464967}}</ref><ref name="Frank">{{Cite journal |vauthors=Frank DA, Augustyn M, Knight WG, Pell T, Zuckerman B |date=March 2001 |title=Growth, development, and behavior in early childhood following prenatal cocaine exposure: a systematic review |journal=JAMA |volume=285 |issue=12 |pages=1613–1625 |doi=10.1001/jama.285.12.1613 |pmc=2504866 |pmid=11268270}}</ref><ref name=AAP20162020>{{cite journal |last1=American Academy of Pediatrics' Committee on Fetus and Newborn and Section on Anesthesiology and Pain Medicine|date=1 February 2016|title= Prevention and Management of Procedural Pain in the Neonate: An Update|url=https://publications.aap.org/pediatrics/article/137/2/e20154271/52762/Prevention-and-Management-of-Procedural-Pain-in|journal=Pediatrics |volume= 137|issue= 2|pages= e20154271|doi=10.1542/peds.2015-4271|pmid= 26810788|access-date=8 September 2024|url-access=subscription}}</ref>

=== Pain ===
{{main|Pain in babies}}
<blockquote>[[Pain management in children|The prevention and alleviation of pain in neonates]], particularly [[Preterm birth|preterm infants]], is important not only because it is [[Medical ethics|ethical]] but also because [[Early childhood trauma|exposure to repeated painful stimuli early in life]] is known to have short- and long-term [[Adverse effect|adverse sequelae]]. These [[Sequela|sequelae]] include [[Homeostasis|physiologic instability]], [[Development of the nervous system in humans|altered brain development, and abnormal neurodevelopment]], [[Somatosensory system|somatosensory]], and [[Stress in early childhood|stress response systems]], which can persist into childhood.<sup>5,–15</sup> [[Nociception|Nociceptive]] pathways are active and functional as early as 25 weeks’ [[Pregnancy|gestation]] and may elicit a generalized or [[Hyperalgesia|exaggerated response]] to [[Noxious stimulus|noxious stimuli]] in immature newborn infants.<sup>16</sup></blockquote><blockquote>[[American Academy of Pediatrics]] February 2016 Policy Statement, reaffirmed July 2020</blockquote><ref name=AAP20162020/>

=== Postnatal depression ===
{{main|Postpartum depression}}
Although there are a large number of studies regarding the effect of maternal depression and postnatal depression on various areas of infant development, they are yet to come to a consensus regarding the true effects. Numerous studies indicate impaired development, while many others find no effect of depression on development.<ref>{{cite journal |last1=Slomian |first1=Justine |last2=Honvo |first2=Germain |last3=Emonts |first3=Patrick |last4=Reginster |first4=Jean-Yves |last5=Bruyère |first5=Olivier |title=Consequences of maternal postpartum depression: A systematic review of maternal and infant outcomes |journal=Women's Health |date=January 2019 |volume=15 |pages=174550651984404 |doi=10.1177/1745506519844044|pmid=31035856 |pmc=6492376 }}</ref><ref>{{cite journal |last1=Parsons |first1=C. E. |last2=Young |first2=K. S. |last3=Rochat |first3=T. J. |last4=Kringelbach |first4=M. L. |last5=Stein |first5=A. |title=Postnatal depression and its effects on child development: a review of evidence from low- and middle-income countries |journal=British Medical Bulletin |date=1 March 2012 |volume=101 |issue=1 |pages=57–79 |doi=10.1093/bmb/ldr047 |pmid=22130907 }}</ref>

A study of 18-month-olds whose mothers had [[depressive symptoms]] while the children were 6 weeks and/or 6 months old found that maternal depression had no effect on the child's [[cognitive development]]. Furthermore, the study indicates that maternal depression combined with a poor home environment is more likely to have an effect on cognitive development than maternal depression alone. However, the authors conclude that it may be that short term depression has no effect, but long term depression could cause more serious problems.<ref name="Piteo 2012">{{Cite journal |vauthors=Piteo AM, Yelland LN, Makrides M |date=August 2012 |title=Does maternal depression predict developmental outcome in 18 month old infants? |journal=Early Human Development |volume=88 |issue=8 |pages=651–655 |doi=10.1016/j.earlhumdev.2012.01.013 |pmid=22361258}}</ref>

A [[longitudinal study]] spanning 7 years found no effect of maternal depression on cognitive development as a whole, however it found that boys are more susceptible to cognitive developmental issues when their mothers had depression.<ref name="Kurstjens" />

This trend is continued in a study of children up to 2 years old, which revealed a significant difference on cognitive development between genders, with girls having a higher score; however girls scored higher regardless of the mother's history of depression. Infants with chronically depressed mothers showed significantly lower scores on the motor and mental scales within the [[Bayley Scales of Infant Development]],<ref name="Cornish 2005">{{Cite journal |vauthors=Cornish AM, McMahon CA, Ungerer JA, Barnett B, Kowalenko N, Tennant C |year=2005 |title=Postnatal depression and infant cognitive and motor development in the second postnatal year: The impact of depression chronicity and infant gender |journal=Infant Behavior and Development |volume=28 |issue=4 |pages=407–417 |doi=10.1016/j.infbeh.2005.03.004}}</ref> contrasting with many older studies.<ref name="Kurstjens" /><ref name="Piteo 2012" />

A similar effect has been found at 11 years: male children of depressed mothers score an average of 19.4 points lower on an IQ test than peers with healthy mothers, while this difference is less pronounced in girls.<ref name="Hay 2001">{{Cite journal |vauthors=Hay DF, Pawlby S, Sharp D, Asten P, Mills A, Kumar R |date=October 2001 |title=Intellectual problems shown by 11-year-old children whose mothers had postnatal depression |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=42 |issue=7 |pages=871–889 |doi=10.1111/1469-7610.00784 |pmid=11693583}}</ref> Three month olds with depressed mothers show significantly lower scores on the Griffiths Mental Development Scale, which covers a range of developmental areas including cognitive, motor and social development.<ref name="Galler 2000">{{Cite journal |vauthors=Galler JR, Harrison RH, Ramsey F, Forde V, Butler SC |date=September 2000 |title=Maternal depressive symptoms affect infant cognitive development in Barbados |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=41 |issue=6 |pages=747–757 |doi=10.1111/1469-7610.00662 |pmid=11039687}}</ref> Furthermore, interactions between depressed mothers and their children may affect social and cognitive abilities in later life.<ref name="Field">{{Cite journal |vauthors=Field T, Healy B, Goldstein S, Guthertz M |year=1990 |title=Behaviour-state matching and synchrony in mother-infant interactions of nondepressed versus depressed dyads |journal=Developmental Psychology |volume=26 |issue=1 |pages=7–14 |doi=10.1037/0012-1649.26.1.7}}</ref>

Maternal depression has been shown to influence the mothers' interaction with her child.<ref name="Reck 2004">{{Cite journal |display-authors=6 |vauthors=Reck C, Hunt A, Fuchs T, Weiss R, Noon A, Moehler E, Downing G, Tronick EZ, Mundt C |year=2004 |title=Interactive regulation of affect in postpartum depressed mothers and their infants: an overview |journal=Psychopathology |volume=37 |issue=6 |pages=272–280 |doi=10.1159/000081983 |pmid=15539778 |s2cid=21040790}}</ref> When communicating with their child, depressed mothers fail to make changes to their [[Intonation (linguistics)|vocal intonation]], and tend to use unstructured vocal behaviours.<ref name="Bettes 1988">{{Cite journal |vauthors=Bettes BA |date=August 1988 |title=Maternal depression and motherese: temporal and intonational features |journal=Child Development |volume=59 |issue=4 |pages=1089–1096 |doi=10.2307/1130275 |jstor=1130275 |pmid=3168616}}</ref> Furthermore, compared to when interacting with healthy mothers, infants interacting with depressed mothers show signs of stress, such as increased pulse and raised [[cortisol|cortisol levels]], and make more use of avoidance behaviours, for example looking away.<ref name="Field" /> Mother-infant interaction at 2 months has been shown to affect the child's cognitive performance at 5 years.<ref>{{Cite journal |vauthors=Murray L, Kempton C, Woolgar M, Hooper R |date=October 1993 |title=Depressed mothers' speech to their infants and its relation to infant gender and cognitive development |journal=Journal of Child Psychology and Psychiatry, and Allied Disciplines |volume=34 |issue=7 |pages=1083–1101 |doi=10.1111/j.1469-7610.1993.tb01775.x |pmid=8245134}}</ref>

Studies have begun to show that other forms of [[psychopathology]] (mental illness) can independently influence infants' and toddlers' subsequent social-emotional development through effects on regulatory processes within the child-parent attachment.<ref>{{Cite journal |vauthors=Schechter DS, Willheim E |date=July 2009 |title=Disturbances of attachment and parental psychopathology in early childhood |journal=Child and Adolescent Psychiatric Clinics of North America |volume=18 |issue=3 |pages=665–686 |doi=10.1016/j.chc.2009.03.001 |pmc=2690512 |pmid=19486844}}</ref> Maternal interpersonal violence-related [[post-traumatic stress disorder]] (PTSD), for example, has been associated with subsequent [[dysregulation]] of emotion and aggression by ages 4–7 years.<ref>{{Cite journal |display-authors=6 |vauthors=Schechter DS, Zygmunt A, Coates SW, Davies M, Trabka K, McCaw J, Kolodji A, Robinson J |date=September 2007 |title=Caregiver traumatization adversely impacts young children's mental representations on the MacArthur Story Stem Battery |journal=Attachment & Human Development |volume=9 |issue=3 |pages=187–205 |doi=10.1080/14616730701453762 |pmc=2078523 |pmid=18007959}}</ref>

=== Maternal drug use ===
==== Cocaine ====
{{main|Prenatal cocaine exposure}}
Research has provided conflicting evidence regarding the severity of effects on children's development posed by [[Drugs in pregnancy#Illicit and recreational drugs|maternal substance use]] during and after pregnancy.<ref name="Frank" /> Children exposed to cocaine in utero weigh less than those not exposed at ages ranging from 6 to 30 months.<ref name="Hurt">{{Cite journal |vauthors=Hurt H, Brodsky NL, Betancourt L, Braitman LE, Malmud E, Giannetta J |date=February 1995 |title=Cocaine-exposed children: follow-up through 30 months |journal=Journal of Developmental and Behavioral Pediatrics |volume=16 |issue=1 |pages=29–35 |doi=10.1097/00004703-199502000-00005 |pmid=7730454 |s2cid=241091}}</ref> Additionally, studies indicate that the head circumference of children exposed to cocaine is lower than those that of children without cocaine exposure.<ref name="Hurt" /><ref>{{Cite journal |vauthors=Azuma SD, Chasnoff IJ |date=September 1993 |title=Outcome of children prenatally exposed to cocaine and other drugs: a path analysis of three-year data |journal=Pediatrics |volume=92 |issue=3 |pages=396–402 |pmid=7689727}}</ref> However, two more recent studies found no significant differences in either measure between those exposed to cocaine and those who were not.<ref>{{Cite journal |vauthors=Richardson GA, Conroy ML, Day NL |year=1996 |title=Prenatal cocaine exposure: effects on the development of school-age children |journal=Neurotoxicology and Teratology |volume=18 |issue=6 |pages=627–634 |doi=10.1016/S0892-0362(96)00121-3 |pmid=8947939|bibcode=1996NTxT...18..627R }}</ref><ref name="Kilbride">{{Cite journal |vauthors=Kilbride H, Castor C, Hoffman E, Fuger KL |date=February 2000 |title=Thirty-six-month outcome of prenatal cocaine exposure for term or near-term infants: impact of early case management |journal=Journal of Developmental and Behavioral Pediatrics |volume=21 |issue=1 |pages=19–26 |doi=10.1097/00004703-200002000-00004 |pmid=10706345 |s2cid=28960955}}</ref>

Maternal cocaine use may also affect the child's [[cognitive development]], with exposed children achieving lower scores on measures of psychomotor and mental development.<ref>{{Cite journal |vauthors=Singer LT, Yamashita TS, Hawkins S, Cairns D, Baley J, Kliegman R |date=May 1994 |title=Increased incidence of intraventricular hemorrhage and developmental delay in cocaine-exposed, very low birth weight infants |journal=The Journal of Pediatrics |volume=124 |issue=5 Pt 1 |pages=765–771 |doi=10.1016/S0022-3476(05)81372-1 |pmc=4181569 |pmid=7513757}}</ref><ref>{{Cite journal |vauthors=Chasnoff IJ, Griffith DR, Freier C, Murray J |date=February 1992 |title=Cocaine/polydrug use in pregnancy: two-year follow-up |journal=Pediatrics |volume=89 |issue=2 |pages=284–289 |doi=10.1542/peds.89.2.284 |pmid=1370867 |s2cid=245214695}}</ref> Again though, there is conflicting evidence, and a number of studies indicate no effect of maternal cocaine use on a child's cognitive development.<ref>{{Cite journal |vauthors=Coles CD, Bard KA, Platzman KA, Lynch ME |year=1999 |title=Attentional response at eight weeks in prenatally drug-exposed and preterm infants |journal=Neurotoxicology and Teratology |volume=21 |issue=5 |pages=527–537 |doi=10.1016/S0892-0362(99)00023-9 |pmid=10492387|bibcode=1999NTxT...21..527C }}</ref><ref>{{Cite journal |display-authors=6 |vauthors=Graham K, Feigenbaum A, Pastuszak A, Nulman I, Weksberg R, Einarson T, Goldberg S, Ashby S, Koren G |date=August 1992 |title=Pregnancy outcome and infant development following gestational cocaine use by social cocaine users in Toronto, Canada |journal=Clinical and Investigative Medicine |volume=15 |issue=4 |pages=384–394 |oclc=121200190 |pmid=1516296 |id={{INIST|5556914}}}}</ref>

Continuing the trend, some studies found maternal [[Stimulant use disorder|cocaine use]] to impair motor development,<ref>{{Cite journal |vauthors=Fetters L, Tronick EZ |date=November 1996 |title=Neuromotor development of cocaine-exposed and control infants from birth through 15 months: poor and poorer performance |journal=Pediatrics |volume=98 |issue=5 |pages=938–943 |doi=10.1542/peds.98.5.938 |pmid=8909489 |s2cid=34639176}}</ref><ref>{{Cite journal |vauthors=Swanson MW, Streissguth AP, Sampson PD, Olson HC |date=October 1999 |title=Prenatal cocaine and neuromotor outcome at four months: effect of duration of exposure |journal=Journal of Developmental and Behavioral Pediatrics |volume=20 |issue=5 |pages=325–334 |doi=10.1097/00004703-199910000-00007 |pmid=10533991}}</ref> while others showed no effect of cocaine use on motor development.<ref name="Hurt" /><ref name="Kilbride" />

==== Other ====
The use of cocaine by pregnant women is not the only drug that can have a negative effect on the fetus. Tobacco, marijuana, and opiates can also affect an unborn child's cognitive and behavioral development.<ref name="Minnes">{{Cite journal |vauthors=Minnes S, Lang A, Singer L |date=July 2011 |title=Prenatal tobacco, marijuana, stimulant, and opiate exposure: outcomes and practice implications |journal=Addiction Science & Clinical Practice |volume=6 |issue=1 |pages=57–70 |citeseerx=10.1.1.290.287 |pmc=3188826 |pmid=22003423}}</ref>

Smoking [[tobacco]] increases pregnancy complications including [[low birth weight]], prematurity, [[placental abruption]], and intrauterine death. After birth it can disturb maternal-infant interactions, reduce IQ, increase the risk of ADHD, and lead to tobacco use in the child.<ref name="Minnes" />

Prenatal [[Cannabis (drug)|marijuana]] exposure may have long-term emotional and behavioral consequences, as at ten-years-old children who had been exposed to the drug during pregnancy reported more depressive symptoms than unexposed peers. Some other effects include executive function impairment, reading difficulty, and delayed emotional regulation.<ref name="Minnes" />

An [[opiate]] drug, such as [[heroin]], in utero decreases birth weight, birth length, and head circumference. Parental opiate exposure may impact the infant's [[central nervous system]] and [[autonomic nervous system]], though the evidence is even more inconsistent than with parental cocaine exposure. There are also some unexpected negative consequences on a child, such as: less rhythmic swallowing, strabismus, and feelings of rejection.<ref name="Minnes" />

=== Malnutrition and Undernutrition ===
Poor nutrition early in life contributes to [[stunted growth|stunting]], and by the age of two or three can be associated with cognitive deficits, poor school achievement, and, later in life, poor social relationships.<ref>{{Cite journal |vauthors=Chilton M, Chyatte M, Breaux J |date=October 2007 |title=The negative effects of poverty & food insecurity on child development |journal=The Indian Journal of Medical Research |volume=126 |issue=4 |pages=262–272 |pmid=18032801}}</ref> [[Malnutrition]] is a large problem in [[developing nations]], and has an important effect on young children's weight and height. Children suffering malnutrition in Colombia weighed less than those living in upper class conditions at the age of 36 months ({{Convert|11.88|kg|lb|abbr=on|disp=sqbr}} compared to {{Convert|14|kg|lb|abbr=on|disp=sqbr}}), and were shorter ({{Convert|85.3|cm|in|abbr=on|disp=sqbr}} versus {{Convert|94|cm|in|abbr=on|disp=sqbr}}).<ref name="Mora" />

Malnutrition during the [[first 1000 days]] of a child's life can cause irreversible physical and mental stunting.<ref>{{Cite book |title=BabyWASH and the 1,000 Days: A Practical Package for Stunting Reduction |vauthors=Dominguez EI |publisher=Action Against Hunger |year=2017 |location=London |language=English}}</ref> Infections and parasites related to poor sanitation and hygiene can impact absorption of nutrients in the gut.<ref name="budge-2019">{{Cite journal |vauthors=Budge S, Parker AH, Hutchings PT, Garbutt C |date=April 2019 |title=Environmental enteric dysfunction and child stunting |journal=Nutrition Reviews |volume=77 |issue=4 |pages=240–253 |doi=10.1093/nutrit/nuy068 |pmc=6394759 |pmid=30753710}}</ref> Adequate [[sanitation]] and [[hygiene]] (rather than just access to food) play a critical role in preventing undernutrition, malnutrition and stunting<ref>{{Cite web |date=2015 |title=Nutrition Puzzles: The Shit Factor. |url=https://sanitationlearninghub.org/2015/05/11/nutrition-puzzles-the-shit-factor/ |archive-url=https://web.archive.org/web/20211213112439/https://sanitationlearninghub.org/2015/05/11/nutrition-puzzles-the-shit-factor/ |archive-date=2021-12-13 |website=Blog on Sanitation Learning Hub Website |vauthors=Scoones I}}{{unreliable source?|date=August 2022}}</ref><ref>{{Cite web |date=2 May 2012 |title=Sanitation and hygiene: undernutrition's blind spot |url=https://sanitationlearninghub.org/2012/05/02/sanitation-and-hygiene-undernutritions-blind-spot/ |access-date=2021-12-13 |website=Sanitation Learning Hub |language=en-GB |vauthors=Chambers R}}{{unreliable source?|date=August 2022}}</ref><ref>{{Cite journal |vauthors=Cumming O, Cairncross S |date=May 2016 |title=Can water, sanitation and hygiene help eliminate stunting? Current evidence and policy implications |journal=Maternal & Child Nutrition |volume=12 |issue=Suppl 1 |pages=91–105 |doi=10.1111/mcn.12258 |pmc=5084825 |pmid=27187910}}</ref><ref name="budge-2019" /> and ensuring normal early childhood development.<ref>{{Cite journal |vauthors=Ngure FM, Reid BM, Humphrey JH, Mbuya MN, Pelto G, Stoltzfus RJ |date=January 2014 |title=Water, sanitation, and hygiene (WASH), environmental enteropathy, nutrition, and early child development: making the links |journal=Annals of the New York Academy of Sciences |volume=1308 |issue=1 |pages=118–128 |bibcode=2014NYASA1308..118N |doi=10.1111/nyas.12330 |pmid=24571214 |s2cid=21280033}}</ref> Malnutrition has been indicated as a negative influence on childhood [[intelligence quotient]] (IQ).<ref>{{Cite journal |display-authors=6 |vauthors=Ivanovic DM, Leiva BP, Pérez HT, Olivares MG, Díaz NS, Urrutia MS, Almagià AF, Toro TD, Miller PT, Bosch EO, Larraín CG |year=2004 |title=Head size and intelligence, learning, nutritional status and brain development. Head, IQ, learning, nutrition and brain |journal=Neuropsychologia |volume=42 |issue=8 |pages=1118–1131 |doi=10.1016/j.neuropsychologia.2003.11.022 |pmid=15093150 |s2cid=2114185}}</ref><ref name="pmid12796242">{{Cite journal |vauthors=Liu J, Raine A, Venables PH, Dalais C, Mednick SA |date=June 2003 |title=Malnutrition at age 3 years and lower cognitive ability at age 11 years: independence from psychosocial adversity |journal=Archives of Pediatrics & Adolescent Medicine |volume=157 |issue=6 |pages=593–600 |doi=10.1001/archpedi.157.6.593 |pmc=3975917 |pmid=12796242}}</ref> Although it has also been suggested that this effect is nullified when parental IQ is considered, implying that this difference is genetic.<ref name="Webb">{{Cite journal |vauthors=Webb KE, Horton NJ, Katz DL |date=April 2005 |title=Parental IQ and cognitive development of malnourished Indonesian children |journal=European Journal of Clinical Nutrition |volume=59 |issue=4 |pages=618–620 |doi=10.1038/sj.ejcn.1602103 |pmid=15688080 |doi-access=free}}</ref>

==== Specific nutrients ====
The effect of [[Iron deficiency|low iron levels]] on cognitive development and IQ has yet to reach consensus.<ref>{{Cite journal |vauthors=Grantham-McGregor S, Ani C |date=February 2001 |title=A review of studies on the effect of iron deficiency on cognitive development in children |journal=The Journal of Nutrition |volume=131 |issue=2S–2 |pages=649S–666S; discussion 666S–668S |doi=10.1093/jn/131.2.649S |pmid=11160596 |doi-access=free}}</ref> Some evidence suggests that even well-nourished children with lower levels of iron and [[Folate deficiency|folate]] (although not at such a level to be considered [[Vitamin deficiency|deficient]]) have a lower IQ than those with higher levels of iron and folate.<ref>{{Cite journal |vauthors=Arija V, Esparó G, Fernández-Ballart J, Murphy MM, Biarnés E, Canals J |year=2006 |title=Nutritional status and performance in test of verbal and non-verbal intelligence in 6 year old children |journal=Intelligence |volume=34 |issue=2 |pages=141–149 |doi=10.1016/j.intell.2005.09.001}}</ref> Furthermore, [[anaemic]] children perform worse on cognitive measures than non-anaemic children.<ref>{{Cite journal |vauthors=Halterman JS, Kaczorowski JM, Aligne CA, Auinger P, Szilagyi PG |date=June 2001 |title=Iron deficiency and cognitive achievement among school-aged children and adolescents in the United States |journal=Pediatrics |volume=107 |issue=6 |pages=1381–1386 |doi=10.1542/peds.107.6.1381 |pmid=11389261}}</ref>

Other nutrients have been strongly implicated in brain development, including iodine and zinc.<ref>{{Cite journal |vauthors=Bryan J, Osendarp S, Hughes D, Calvaresi E, Baghurst K, van Klinken JW |date=August 2004 |title=Nutrients for cognitive development in school-aged children |journal=Nutrition Reviews |volume=62 |issue=8 |pages=295–306 |doi=10.1111/j.1753-4887.2004.tb00055.x |pmid=15478684|doi-access=free }}</ref> Iodine is required for the formation of [[thyroid hormones]] necessary for brain development.<ref>Reavley N. (1998). ''Vitamins, etc.'' Melbourne: Bookman Media Pty Ltd</ref> [[Iodine deficiency]] may reduce IQ by an average of 13.5 points compared to healthy individual.<ref>{{Cite book |title=The Damaged Brain of Iodine Deficiency: Cognitive, Behavioral, Neuromotor, Educative Aspects |vauthors=Bleichrodt N, Born MP |date=1994 |publisher=Cognizant Communication Corporation |isbn=978-1-882345-03-8 |veditors=Stanbury JB |location=New York |pages=195–200 |chapter=Chapter 19: A meta-analysis of research on iodine and its relationship to cognitive development |chapter-url=http://www.ceecis.org/iodine/04a_consequences/02_int/chapt_on_i_brain.pdf |archive-url=https://web.archive.org/web/20190130233020/http://www.ceecis.org/iodine/04a_consequences/02_int/chapt_on_i_brain.pdf |archive-date=30 January 2019}}</ref> [[Zinc deficiency]] has also been shown to slow childhood growth and development.<ref>{{Cite journal |vauthors=Brown KH, Peerson JM, Rivera J, Allen LH |date=June 2002 |title=Effect of supplemental zinc on the growth and serum zinc concentrations of prepubertal children: a meta-analysis of randomized controlled trials |journal=The American Journal of Clinical Nutrition |volume=75 |issue=6 |pages=1062–1071 |doi=10.1093/ajcn/75.6.1062 |pmid=12036814 |doi-access=free}}</ref><ref>{{Cite journal |display-authors=6 |vauthors=Bhutta ZA, Black RE, Brown KH, Gardner JM, Gore S, Hidayat A, Khatun F, Martorell R, Ninh NX, Penny ME, Rosado JL, Roy SK, Ruel M, Sazawal S, Shankar A |date=December 1999 |title=Prevention of diarrhea and pneumonia by zinc supplementation in children in developing countries: pooled analysis of randomized controlled trials. Zinc Investigators' Collaborative Group |journal=The Journal of Pediatrics |volume=135 |issue=6 |pages=689–697 |doi=10.1016/S0022-3476(99)70086-7 |pmid=10586170|doi-access=free }}</ref> Zinc supplementation appears to be beneficial for growth in infants under six months old.<ref>{{Cite journal |vauthors=Lassi ZS, Kurji J, Oliveira CS, Moin A, Bhutta ZA |date=April 2020 |title=Zinc supplementation for the promotion of growth and prevention of infections in infants less than six months of age |journal=The Cochrane Database of Systematic Reviews |volume=2020 |issue=4 |pages=CD010205 |doi=10.1002/14651858.CD010205.pub2 |pmc=7140593 |pmid=32266964}}</ref>

=== Socioeconomic status ===
[[Socioeconomic status]] is measured primarily based on income, educational attainment and occupation.<ref>{{Cite web |title=Socioeconomic Status |url=http://www.apa.org/topics/socioeconomic-status/index.aspx |archive-url=https://web.archive.org/web/20190131005824/http://www.apa.org/topics/socioeconomic-status/index.aspx |archive-date=31 January 2019 |publisher=American Psychological Association}}</ref> Investigations into the role of socioeconomic factors on child development repeatedly show that continual [[poverty]] is more harmful on [[intelligence quotient|IQ]],<ref name="Smith">{{Cite book |title=Consequences of growing up poor |vauthors=Smith JR, Brooks-Gunn J, Klebanov P |date=1997 |publisher=Russell Sage Foundation |isbn=978-0-87154-143-7 |veditors=Duncan GJ, Brooks-Gunn J |location=New York |chapter=The consequences of living in poverty for young children's cognitive and verbal ability and early school achievement.}} {{page needed|date=August 2022}}</ref> and cognitive abilities<ref name="Schoon 2011">{{Cite journal |vauthors=Schoon I, Jones E, Cheng H, Maughan B |date=August 2012 |title=Family hardship, family instability, and cognitive development |journal=Journal of Epidemiology and Community Health |volume=66 |issue=8 |pages=716–722 |doi=10.1136/jech.2010.121228 |pmid=21507894 |s2cid=24683428}}</ref> than short-term poverty.

Children in families who experience persistent financial hardships and poverty have significantly impaired cognitive abilities compared to those in families who do not face these issues.<ref name="Schoon 2011" /> Poverty can also cause a number of other factors shown to effect child development, such as poor academic success, less family involvement, iron deficiency, infections, a lack of stimulation,<ref>{{Cite journal |vauthors=Bradley RH, Corwyn RF |date=2002 |title=Socioeconomic status and child development |journal=Annual Review of Psychology |volume=53 |pages=371–399 |doi=10.1146/annurev.psych.53.100901.135233 |pmid=11752490}}</ref> and malnutrition. Poverty also increases the risk of [[lead poisoning]] due to lead paint found on the walls of some houses;<ref name="Brooks-Gunn 1997">{{Cite journal |vauthors=Brooks-Gunn J, Duncan GJ |year=1997 |title=The effects of poverty on children |url=https://www.princeton.edu/futureofchildren/publications/docs/07_02_03.pdf |url-status=dead |journal=The Future of Children |volume=7 |issue=2 |pages=55–71 |doi=10.2307/1602387 |jstor=1602387 |pmid=9299837 |archive-url=https://web.archive.org/web/20170617144312/http://www.princeton.edu/futureofchildren/publications/docs/07_02_03.pdf |archive-date=2017-06-17 |access-date=2012-12-06}}</ref> child blood levels of lead increase as income decreases.<ref>{{Cite journal |vauthors=Brody DJ, Pirkle JL, Kramer RA, Flegal KM, Matte TD, Gunter EW, Paschal DC |date=July 1994 |title=Blood lead levels in the US population. Phase 1 of the Third National Health and Nutrition Examination Survey (NHANES III, 1988 to 1991) |journal=JAMA |volume=272 |issue=4 |pages=277–283 |doi=10.1001/jama.272.4.277 |pmid=8028140}}</ref> Income based poverty is associated with a 6–13 point reduction in IQ for those earning half of the [[poverty threshold]] compared to those earning twice the poverty threshold,<ref name="Smith" /> and children coming from households featuring continual or temporary poverty perform lower than children in middle-class families.<ref name="Schoon 2011" />

Parental [[educational attainment]] is the most significant socioeconomic factor in predicting the child's cognitive abilities,<ref name="DeGarmo 2003">{{Cite journal |vauthors=DeGarmo DS, Forgatch MS, Martinez CR |year=2003 |title=Parenting of divorced mothers as a link between social status and boys' academic outcomes: unpacking the effects of socioeconomic status |journal=Child Development |volume=70 |issue=5 |pages=1231–1245 |doi=10.1111/1467-8624.00089 |pmid=10546342}}</ref> as those with a mother with a high IQ are likely to have higher IQs themselves.<ref name="Webb" /><ref>{{Cite journal |vauthors=Honzik MP |date=June 1957 |title=Developmental studies of parent-child resemblance in intelligence |journal=Child Development |volume=28 |issue=2 |pages=215–228 |doi=10.2307/1125882 |jstor=1125882 |pmid=13427072}}</ref> Similarly, maternal [[Work (human activity)|occupation]] is associated with better cognitive achievement. Those whose mothers' job entails problem-solving are more likely to be given stimulating tasks and games, and are likely to achieve more advanced verbal competency.<ref name="Parcel 1990">{{Cite journal |vauthors=Ferguson MK |date=February 2022 |title=Caustic Ingestion-The Haves and the Have Nots |journal=JAMA Surgery |volume=157 |issue=2 |pages=119 |doi=10.2307/2786675 |jstor=2786675 |pmid=34878518}}</ref>

On the other hand, maternal employment is associated with slightly lower test scores, regardless of socioeconomic status. Counterintuitively, maternal employment results in more disadvantages the higher the socioeconomic status, as these children are being removed from a more [[Environmental enrichment|enriching environment]] to be put in [[child care]], though the quality of the child care must be considered. Low income children tend to be cared for by grandparents or extended family<ref name="Ruhm2004">{{Cite journal |vauthors=Ruhm CJ |date=2004 |title=Parental Employment and Child Cognitive Development |url=http://www.nber.org/papers/w7666.pdf |journal=The Journal of Human Resources |volume=39 |issue=1 |pages=155–192 |doi=10.2307/3559009 |jstor=3559009}}</ref> and therefore form strong bonds with family. High income children tend to be cared for in a child care setting or in home care such as with a nanny. If the mother is highly educated, this can be a disadvantage to the child.<ref>{{cite journal | vauthors = Jackson M, Kiernan K, McLanahan S | title = Maternal Education, Changing Family Circumstances, and Children's Skill Development in the United States and UK | journal = The Annals of the American Academy of Political and Social Science | volume = 674 | issue = 1 | pages = 59–84 | date = November 2017 | pmid = 29563643 | pmc = 5857959 | doi = 10.1177/0002716217729471 }}</ref>

Even with quality of care controlled for, studies still found that full-time work within the first year was correlated with negative effects on child development.<ref name="Ruhm2004" /> Children whose mothers work are also less likely to receive regular well-baby doctor visits and less likely to be [[breastfed]],<ref>{{Cite journal |author-link2=Jennifer Hill |vauthors=Berger LM, Hill J, Waldfogel J |date=February 2005 |title=Maternity leave, early maternal employment and child health and development in the US. |journal=The Economic Journal |volume=115 |issue=501 |pages=29–47 |doi=10.1111/j.0013-0133.2005.00971.x |s2cid=80026676}}</ref> which has been proven to improve developmental results. Effects are felt more strongly when women resume full-time work within the first year of the child's life.<ref>{{Cite journal |vauthors=Baum II CL |date=April 2003 |title=Does Early Maternal Employment Harm Child Development? An Analysis of the Potential Benefits of Leave Taking |journal=Journal of Labor Economics |volume=21 |issue=2 |pages=409–448 |doi=10.1086/345563 |s2cid=222330144}}</ref><ref>{{Cite journal |author-link=Jennifer Hill |vauthors=Hill JL, Waldfogel J, Brooks-Gunn J, Han WJ |date=November 2005 |title=Maternal employment and child development: a fresh look using newer methods |journal=Developmental Psychology |volume=41 |issue=6 |pages=833–850 |doi=10.1037/0012-1649.41.6.833 |pmid=16351331}}</ref> These effects may be due in part to pre-existing differences between mothers who return to work and those who do not, such as differences in character or reason for returning to work.<ref>{{Cite journal |vauthors=Brooks-Gunn J, Han WJ, Waldfogel J |date=July 2002 |title=Maternal employment and child cognitive outcomes in the first three years of life: the NICHD Study of Early Child Care. National Institute of Child Health and Human Development |journal=Child Development |volume=73 |issue=4 |pages=1052–1072 |doi=10.1111/1467-8624.00457 |pmid=12146733}}</ref>

Low-income families are less likely to provide a stimulating home learning environment to their children due to time constraints and financial stress.<ref>{{Cite book |title=Defending Childhood: Keeping the Promise of Early Education |vauthors=Bowman B, Ray A |date=2012 |publisher=Teachers College Press |veditors=Falk B |pages=63–85 |chapter=Low-Income Families and Young Children's Development and School Success}}</ref> Compared to two-parent households, children with a [[Single parent|single-parent]] households have greater economic vulnerability and less parental involvement, leading to worse social, behavioral, educational, or cognitive outcomes.<ref>{{Cite book |title=Building an Opportunity Society |vauthors=Solomon LD |date=2014 |publisher=Transaction Publishers |page=58 |chapter=Family Structure Trends and Child Well-Being}}</ref>

A child's academic achievement is influenced by parents' educational attainment, [[Parenting styles|parenting style]], and parental investment in their child's cognitive and educational success. Higher-income families are able to afford learning opportunities both inside and outside the classroom.<ref>{{Cite book |title=Building an Opportunity Society |vauthors=Solomon LD |date=2014 |publisher=Transaction Publishers |page=27 |chapter=Economic Immobility and Income and Wealth Inequalities: Realities and Casual Factors}}</ref> Poverty-stricken children have fewer opportunities for stimulating recreational activities, often missing out on trips to libraries or museums, and are unable to access a tutor to help with problematic academic areas.<ref>{{Cite journal |vauthors=Bradley RH, Corwyn RF, McAdoo HP, Coll CG |date=November 2001 |title=The home environments of children in the United States part I: variations by age, ethnicity, and poverty status |journal=Child Development |volume=72 |issue=6 |pages=1844–1867 |doi=10.1111/1467-8624.t01-1-00382 |pmid=11768149}}</ref>

A further factor in a child's educational attainment involves the school environment, more specifically teacher expectations and attitudes.<ref name="McLoyd">{{Cite book |title=Social and Emotional Adjustment and Family Relations in Ethnic Minority Families |vauthors=McLoyd VC |date=2013 |publisher=Routledge |isbn=978-1-135-45262-9 |veditors=Taylor RD, Wang MC |pages=7–34 |chapter=The impact of poverty and low socioeconomic status on the socioemotional functioning of African-American children and adolescents: Mediating effects |chapter-url=https://books.google.com/books?id=A4UuAgAAQBAJ&pg=PT23}}</ref> If teachers perceive low-SES children as being less academically able then they may provide them with less attention and reinforcement.<ref name="McLoyd" /> On the other hand, when schools make an effort to increase family and school involvement, children perform better on state tests.<ref>{{Cite book |title=Defending Childhood: Keeping the Promise of Early Education |vauthors=Bowman B, Ray A |date=2012 |publisher=Teachers College Press |isbn=978-0-8077-5310-1 |veditors=Falk B |pages=63–85 |chapter=Low-Income Families and Young Children's Development and School Success |chapter-url=https://books.google.com/books?id=Nmgk8h5GrbgC&pg=PA63}}</ref>

=== Parasites ===
Diarrhea caused by the parasitic disease [[Giardiasis]] is associated with lower IQ.<ref>{{Cite journal |display-authors=6 |vauthors=Ajjampur SS, Koshy B, Venkataramani M, Sarkar R, Joseph AA, Jacob KS, Ward H, Kang G |year=2011 |title=Effect of cryptosporidial and giardial diarrhoea on social maturity, intelligence and physical growth in children in a semi-urban slum in south India |journal=Annals of Tropical Paediatrics |volume=31 |issue=3 |pages=205–212 |doi=10.1179/1465328111Y.0000000003 |pmid=21781414 |s2cid=4667351}}</ref> Parasitic worms ([[helminths]]) are associated with nutritional deficiencies known to be a risk to child development.<ref>{{Cite web |date=1987 |title=Prevention and control of intestinal parasitic infections |url=http://whqlibdoc.who.int/trs/WHO_TRS_749.pdf |archive-url=https://web.archive.org/web/20150226064637/http://whqlibdoc.who.int/trs/WHO_TRS_749.pdf |archive-date=26 February 2015 |website=World Health Organisation}}</ref> Intestinal parasitism is one of the most neglected tropical diseases in the developed world, and harboring of this parasite could have several health implications in children that negatively affect childhood development and [[morbidity]].  Prolonged exposure to [[Fecal–oral route|faecally-transmitted infections]], including [[environmental enteropathy]], other intestinal infections, and parasites during early childhood can lead to irreversible [[Stunted growth|stunting]].<ref>{{Cite web |date=2014 |title=Reframing Undernutrition: Faecally-Transmitted Infections and the 5 As |url=https://sanitationlearninghub.org/resource/reframing-undernutrition-faecally-transmitted-infections-and-the-5-as/ |archive-url=https://web.archive.org/web/20211213112502/https://sanitationlearninghub.org/resource/reframing-undernutrition-faecally-transmitted-infections-and-the-5-as/ |archive-date=13 December 2021 |website=IDS Working Paper 450 |publisher=Institute of Development Studies |vauthors=Chambers R, von Medeazza G |location=Brighton}}</ref>  Reducing the prevalence of these parasites can be a benefit in child growth, development, and educational outcome.<ref>{{Cite journal |vauthors=Opara KN, Udoidung NI, Opara DC, Okon OE, Edosomwan EU, Udoh AJ |year=2012 |title=The Impact of Intestinal Parasitic Infections on the Nutritional Status of Rural and Urban School-Aged Children in Nigeria |journal=International Journal of MCH and AIDS |volume=1 |issue=1 |pages=73–82 |doi=10.21106/ijma.8 |pmc=4948163 |pmid=27621960}}</ref>

=== Toxin exposure ===
High levels of lead in the blood is associated with attention deficits,<ref name="Calderon 2001">{{Cite journal |display-authors=6 |vauthors=Calderón J, Navarro ME, Jimenez-Capdeville ME, Santos-Diaz MA, Golden A, Rodriguez-Leyva I, Borja-Aburto V, Díaz-Barriga F |date=February 2001 |title=Exposure to arsenic and lead and neuropsychological development in Mexican children |journal=Environmental Research |volume=85 |issue=2 |pages=69–76 |bibcode=2001ER.....85...69C |doi=10.1006/enrs.2000.4106 |pmid=11161656}}</ref> while [[arsenic poisoning]] has a negative effect on both verbal IQ and on total [[intelligence quotient]].<ref name="Calderon 2001" /> [[Manganism|Manganese poisoning]] due to levels in drinking water is also associated with a reduced IQ of 6.2 points between the highest and lowest level of poisoning.<ref>{{Cite journal |display-authors=6 |vauthors=Bouchard MF, Sauvé S, Barbeau B, Legrand M, Brodeur MÈ, Bouffard T, Limoges E, Bellinger DC, Mergler D |date=January 2011 |title=Intellectual impairment in school-age children exposed to manganese from drinking water |journal=Environmental Health Perspectives |volume=119 |issue=1 |pages=138–143 |doi=10.1289/ehp.1002321 |pmc=3018493 |pmid=20855239|bibcode=2011EnvHP.119..138B }}</ref>

Prenatal exposure to various [[pesticide]]s including organophosphates,<ref name="Bouchard 2011">{{Cite journal |display-authors=6 |vauthors=Bouchard MF, Chevrier J, Harley KG, Kogut K, Vedar M, Calderon N, Trujillo C, Johnson C, Bradman A, Barr DB, Eskenazi B |date=August 2011 |title=Prenatal exposure to organophosphate pesticides and IQ in 7-year-old children |journal=Environmental Health Perspectives |volume=119 |issue=8 |pages=1189–1195 |doi=10.1289/ehp.1003185 |pmc=3237357 |pmid=21507776|bibcode=2011EnvHP.119.1189B }}</ref> and [[chlorpyrifos]]<ref>{{Cite journal |vauthors=Rauh V, Arunajadai S, Horton M, Perera F, Hoepner L, Barr DB, Whyatt R |date=August 2011 |title=Seven-year neurodevelopmental scores and prenatal exposure to chlorpyrifos, a common agricultural pesticide |journal=Environmental Health Perspectives |volume=119 |issue=8 |pages=1196–1201 |doi=10.1289/ehp.1003160 |pmc=3237355 |pmid=21507777|bibcode=2011EnvHP.119.1196R }}</ref> has also been linked to reduced IQ score. [[Organophosphate poisoning|Organophosphates]] have been specifically linked to poorer [[working memory]], verbal comprehension, perceptual reasoning and processing speed.<ref name="Bouchard 2011" />

=== Other ===
[[Intrauterine growth restriction]] is associated with learning deficits in childhood, and as such, is related to lower IQ.<ref name="Low 1992">{{Cite journal |vauthors=Low JA, Handley-Derry MH, Burke SO, Peters RD, Pater EA, Killen HL, Derrick EJ |date=December 1992 |title=Association of intrauterine fetal growth retardation and learning deficits at age 9 to 11 years |journal=American Journal of Obstetrics and Gynecology |volume=167 |issue=6 |pages=1499–1505 |doi=10.1016/0002-9378(92)91727-R |pmid=1471654}}</ref> Cognitive development can also be harmed by childhood exposure to violence and trauma, including [[spousal abuse]] between the parents and [[sexual abuse]].<ref name="Bosquet Enlow 2012">{{Cite journal |vauthors=Enlow MB, Egeland B, Blood EA, Wright RO, Wright RJ |date=November 2012 |title=Interpersonal trauma exposure and cognitive development in children to age 8 years: a longitudinal study |journal=Journal of Epidemiology and Community Health |volume=66 |issue=11 |pages=1005–1010 |doi=10.1136/jech-2011-200727 |pmc=3731065 |pmid=22493459}}</ref><ref>{{Cite book |title=Handbook of Infant Mental Health |vauthors=Schechter DS, Willheim E |date=2009 |publisher=Guilford Press, Inc |veditors=Zeanah CH |edition=3rd |location=New York |pages=197–214 |chapter=The Effects of Violent Experience and Maltreatment on Infants and Young Children}}</ref>

== Neglect ==
{{Coatrack section|date=July 2023|details=see talk page}}
When a child is unable to meet their developmental goals because they have not been provided with the correct amount of care, stimulation or nutrition this situation is commonly referred to as [[child neglect]]. It is the most widespread form of [[child abuse]], accounting for 78% of all child abuse cases in the United States in 2010 alone. Scientific studies show that child neglect can have lifelong consequences for children.<ref>{{Cite web |date=2015 |title=Neglect |url=https://developingchild.harvard.edu/science/deep-dives/neglect/ |archive-url=https://web.archive.org/web/20180912022158/https://developingchild.harvard.edu/science/deep-dives/neglect/ |archive-date=12 September 2018 |website=Center on the Developing Child |publisher=Harvard University}}</ref>

=== Assessing and identifying ===
Assessing and identifying neglect pose a number of challenges for practitioners. Given that neglect is a dynamic between the child's development and levels of nurturance, the question in identifying neglect, becomes one of where do you start, with the child's development or with the levels of nurturance?{{citation needed|date=July 2023}}

==== Development focused methods ====
Some professionals identify neglect by measuring the developmental levels of a child, as if those levels are normal, one can, by definition, conclude that a child is not being neglected. Measured areas of development can include weight, height, stamina, social and emotional responses, speech and motor development. As all these features go into making a medical assessment of whether a child is [[thriving]], a professional looking to start an assessment of neglect might start with information collected by a doctor.<ref name="McTavish_2020">{{cite journal | vauthors = McTavish JR, Gonzalez A, Santesso N, MacGregor JC, McKee C, MacMillan HL | title = Identifying children exposed to maltreatment: a systematic review update | journal = BMC Pediatrics | volume = 20 | issue = 1 | pages = 113 | date = March 2020 | pmid = 32145740 | pmc = 7060650 | doi = 10.1186/s12887-020-2015-4 | doi-access = free }}</ref>

Infants are often weighed and measured when seen by their [[pediatrician]] for well-baby check-ups. The physician initiates a more complete evaluation when the infant's development and functioning are found to be delayed. Then social work staff could consult medical notes to establish if the baby or child is failing to thrive, as a first step in a pathway towards identifying neglect. If developmental levels are below normal, the identification of neglect then requires the professional to establish if this can be put down to the level of nurturance experienced by the child. Developmental delays caused by genetic conditions or disease need to be discounted, as they do not have their basis in a lack of nurturance.<ref name="McTavish_2020" />

=== Starting the assessment ===
Besides routine pediatrician visits, another way of starting the process of identifying neglect is to determine if the child is experiencing a level of nurturance lower than that considered necessary to support normal development,<ref name="Daniel, B. 20112">{{Cite book |title=Recognizing and Helping the Neglected Child: Evidence-Based Practice for Assessment and Intervention |vauthors=Scott J, Daniel B, Taylor J, Derbyshire D, Neilson D |date=2011 |publisher=Jessica Kingsley Publishers |location=London}}</ref> which might be unique to the child's age, gender and other factors.<ref name="Daniel, B. 20112" /> Exactly how to ascertain what a particular child needs, without referring back to their level of development, is not something theory and policy on neglect is clear about. Furthermore, determining whether a child is getting the requisite level of nurturance needs to take into account not just the intensity of the nurturance, but also the duration and frequency of the nurturance.{{citation needed|date=July 2023}}

Children may experience varying and low levels of certain types of nurturance across a day and from time to time, however, the levels of nurturance should never cross thresholds of intensity, duration and frequency. For this reason, professionals must keep detailed histories of care provision, which demonstrate the duration of subnormal exposure to care, stimulation, and nutrition.<ref>{{cite journal | vauthors = Zeanah CH, Humphreys KL | title = Child Abuse and Neglect | journal = Journal of the American Academy of Child and Adolescent Psychiatry | volume = 57 | issue = 9 | pages = 637–644 | date = September 2018 | pmid = 30196867 | pmc = 6615750 | doi = 10.1016/j.jaac.2018.06.007 }}</ref>

Common guidance suggests professionals should focus on the levels of nurturance provided by the carers of the child, as neglect is understood as an issue of the parents' behaviour towards the child.<ref>{{Cite book |url=https://www.ojp.gov/ncjrs/virtual-library/abstracts/child-neglect-current-definitions-and-models-review-child-neglect |title=Child Neglect: Current Definitions and Models. A Review of the Literature, 1993-1998. |vauthors=Sullivan S |date=2000 |publisher=Family Violence Prevention Unit, Health Canada}}</ref> Some authors feel that establishing the failure of parents and caregivers to provide care is sufficient to conclude that neglect is occurring.<ref>{{Cite book |url=http://eprints.lincoln.ac.uk/id/eprint/4859/1/Hicks_and_Stein_Neglect_Matters.pdf |title=Neglect matters: a multi-agency guide for professionals working together on behalf of teenagers. |vauthors=Hicks L, Stein M |date=March 2010 |publisher=Department for Children, Schools and Families |location=London}}</ref><ref>{{Cite web |date=2014 |title=Child Neglect: The Scandal That Never Breaks |url=https://www.actionforchildren.org.uk/media/3213/child-neglect-the-scandal-that-never-breaks_march2014.pdf |archive-url=https://web.archive.org/web/20151120094034/https://www.actionforchildren.org.uk/media/3213/child-neglect-the-scandal-that-never-breaks_march2014.pdf |archive-date=20 November 2015 |website=Action for Children |location=London}}</ref> One definition is that, "a child experiences neglect when the adults who look after them fail to meet their needs", which clearly defines neglect as a matter of parental performance.

This raises the question about what level of nurturance a carer or parent needs to fall under to provoke developmental delay, and how one goes about measuring that accurately. This definition, which focuses on the stimulation provided by the carer, can be subject to critique. Neglect is about the child's development being adversely affected by the levels of nurturance, but the carers' provision of nurturance is not always a good indicator of the level of nurturance received by the child. Neglect may be occurring at school, outside of parental care. The child may be receiving nurturance from siblings or through a boarding school education, which compensates for the lack of nurturance provided by the parents.{{citation needed|date=July 2023}}

=== Linking to stimulation ===
Neglect is a process whereby children experience [[Global developmental delay|developmental delay]] owing to experiencing insufficient levels of nurturance. In practice, this means that when starting an assessment of neglect by identifying developmental delay one needs to then check the levels of nurturance received by the child. While some guidance on identifying neglect urges practitioners to measure developmental levels, other guidance focuses on how developmental levels can be attributed to parental behaviour.<ref>{{Cite report |title=Official Report |date=15 January 2013 |id=Col 1774 |work=Scottish Parliament Education and Culture Committee}}</ref> However, the narrow focus on parental behaviour can be criticised for unnecessarily ruling out the possible effect of institutionalised neglect, e.g. neglect at school.

If one starts by concluding that the levels of nurture received by the child are insufficient, one then needs to consider the developmental levels achieved by the child. Further challenges arise, however, as even when one has established developmental delay and exposure to low levels of nurture, one needs to rule out the possibility that the link between the two is coincidental. The developmental delay may be caused by a genetic disorder, disease or physical, sexual or emotional abuse. The developmental delay may be caused by a mixture of underexposure to nurture, abuse, genetics, and disease.{{citation needed|date=July 2023}}

=== Measuring tools ===
[[The Graded Care Profile Tool]] is a practice tool which gives an objective measure of the quality of care in terms of a parent/carer's commitment. It was developed in the UK.<ref>{{Cite web |date=2015 |title=What is the Graded Care Profile Tool? |url=http://lutonlscb.org.uk/graded.html |archive-url=https://web.archive.org/web/20151121053106/http://lutonlscb.org.uk/graded.html |archive-date=21 November 2015 |website=Luton Safeguarding Children's Board}}</ref>

The [[North Carolina Family Assessment Scale]] is a tool that can be used by a practitioner to explore whether neglect is taking place across a range of family functioning areas.<ref>{{Cite web |date=2015 |title=Overview of Assessment Tools |url=http://www.nfpn.org/portals/0/documents/assessment_tools_overview.pdf |archive-url=https://web.archive.org/web/20151120225552/http://www.nfpn.org/portals/0/documents/assessment_tools_overview.pdf |archive-date=20 November 2015 |website=National Family Preservation Network}}</ref>

=== Intervention programs ===
Early intervention programs and treatments include individual counselling, family and group counselling, social support services, behavioural skills training programs to eliminate problematic behaviour and teach parents appropriate parenting behaviour.<ref>{{cite journal | vauthors = van der Put CE, Assink M, Gubbels J, Boekhout van Solinge NF | title = Identifying Effective Components of Child Maltreatment Interventions: A Meta-analysis | journal = Clinical Child and Family Psychology Review | volume = 21 | issue = 2 | pages = 171–202 | date = June 2018 | pmid = 29204796 | pmc = 5899109 | doi = 10.1007/s10567-017-0250-5 }}</ref>

[[Video interaction guidance]] is a [[video feedback intervention]] through which a "guider" helps a client to enhance communication within relationships. The client is guided to analyse and reflect on video clips of their own interactions.<ref>{{Cite web |date=17 December 2012 |title=What is Video Interaction Guidance? (VIG) |url=https://www.youtube.com/watch?v=YRVaL_ZlxHs |archive-url=https://web.archive.org/web/20160603013842/https://www.youtube.com/watch?v=YRVaL_ZlxHs |archive-date=3 June 2016 |access-date=31 October 2016 |website=YouTube}}</ref><ref>{{Cite web |date=18 July 2016 |title=Video Interaction Guidance (VIG) |url=http://vimeo.com/41413218 |archive-url=https://web.archive.org/web/20160822174625/https://vimeo.com/41413218 |archive-date=22 August 2016 |access-date=31 October 2016 |website=North East Autism =Society |via=vimeo.com}}</ref> Video Interaction Guidance has been used where concerns have been expressed over possible parental neglect in cases where the focus child is aged 2–12, and where the child is not the subject of a child protection plan.<ref>{{Cite report |url=https://letterfromsanta.nspcc.org.uk/globalassets/documents/evaluation-of-services/video-interactive-guidance-vig-evaluation-report.pdf |title=Child neglect and Video Interaction Guidance: key findings and executive summary of an NSPCC service offered to parents where initial concerns of neglect have been noted |publisher=National Society for the Prevention of Cruelty to Children |vauthors=Whalley P, Williams M |year=2015}} {{page needed|date=August 2022}}</ref>

[[The SafeCare programme]] is a preventive programme working with parents of children under 6 years old who are at risk of significant harm through neglect. The programme is delivered in the home by trained practitioners, and is 18 to 20 sessions focused on 3 key areas: parent-infant/child interaction, home safety and child health.<ref name="nspcc.org.uk2">{{Cite report |url=https://library.nspcc.org.uk/HeritageScripts/Hapi.dll/retrieve2?SetID=4195141F-93F8-4BB2-BE96-4FEBD1B47706&SearchTerm0=SafeCare%3A%20evidence%20from%20a%20home%20based%20parenting%20programme%20for%20neglect&SearchPrecision=20&SortOrder=Y1&Offset=1&Direction=%2E&Dispfmt=F&Dispfmt_b=B27&Dispfmt_f=F13&DataSetName=LIVEDATA |title=SafeCare: evidence from a home based parenting programme for neglect |vauthors=Churchill G |year=2015}}{{page needed|date=August 2022}}</ref>

[[Triple P (Parenting Program)]] is a positive parenting program. It is a multilevel parenting and family support strategy. The idea behind it is that if parents are educated on proper parenting and given the appropriate resources, it could help decrease the number of child neglect cases.<ref name="nichd.nih.gov">{{Cite web |date=2006 |title=Descriptions of NICHD career development projects related to child abuse, child maltreatment, and child violence |url=https://www.nichd.nih.gov/sites/default/files/news/resources/spotlight/Documents/career_development_child_abuse.pdf |archive-url=https://web.archive.org/web/20211010022842/https://www.nichd.nih.gov/sites/default/files/news/resources/spotlight/Documents/career_development_child_abuse.pdf |archive-date=10 October 2021 |website=National Institutes of Health |vauthors=Slack KS}}</ref>

== See also ==
{{Portal|Psychology|Biology}}
{{div col|colwidth=25em}}
*[[Attachment theory]]
*[[Birth order]]
*[[Child development stages]]
*[[Child life specialist]]
*[[Child prodigy]]
*[[Clinical social work]]
*[[Critical period]]
*[[Developmental psychology]]
*[[Developmental psychobiology]]
*[[Developmental psychopathology]]
*[[Early childhood education]]
*[[Evolutionary developmental psychology]]
*[[Pedagogy]]
*[[Play (activity)|Play]]
*[[Psychoanalytic infant observation]]
*[[Child development in Africa]]
*[[Child development in India]]

{{div col end}}

== References ==
{{reflist|30em}}

== Further reading ==
{{refbegin|30em}}
* {{Cite journal |display-authors=6 |vauthors=Berl MM, Duke ES, Mayo J, Rosenberger LR, Moore EN, VanMeter J, Ratner NB, Vaidya CJ, Gaillard WD |date=August 2010 |title=Functional anatomy of listening and reading comprehension during development |journal=Brain and Language |volume=114 |issue=2 |pages=115–125 |doi=10.1016/j.bandl.2010.06.002 |pmc=2962416 |pmid=20656105}}
* {{Cite journal |vauthors=Bishop DV, Anderson M, Reid C, Fox AM |date=May 2011 |title=Auditory development between 7 and 11 years: an event-related potential (ERP) study |journal=PLOS ONE |volume=6 |issue=5 |pages=e18993 |bibcode=2011PLoSO...618993B |doi=10.1371/journal.pone.0018993 |pmc=3090390 |pmid=21573058 |doi-access=free |veditors=Koenig T}}
* {{Cite journal |vauthors=Friederici AD, Brauer J, Lohmann G |year=2011 |title=Maturation of the language network: from inter- to intrahemispheric connectivities |journal=PLOS ONE |volume=6 |issue=6 |pages=e20726 |bibcode=2011PLoSO...620726F |doi=10.1371/journal.pone.0020726 |pmc=3113799 |pmid=21695183 |doi-access=free |veditors=Rodriguez-Fornells A}}
* {{Cite journal |vauthors=Giedd JN, Rapoport JL |date=September 2010 |title=Structural MRI of pediatric brain development: what have we learned and where are we going? |journal=Neuron |volume=67 |issue=5 |pages=728–734 |doi=10.1016/j.neuron.2010.08.040 |pmc=3285464 |pmid=20826305}}
* {{Cite journal |vauthors=Hu Z, Chan RC, McAlonan GM |date=February 2010 |title=Maturation of social attribution skills in typically developing children: an investigation using the social attribution task |journal=Behavioral and Brain Functions |volume=6 |pages=10 |doi=10.1186/1744-9081-6-10 |pmc=2830993 |pmid=20181076 |doi-access=free }}
* {{Cite journal |vauthors=Jolles DD, Crone EA |year=2012 |title=Training the developing brain: a neurocognitive perspective |journal=Frontiers in Human Neuroscience |volume=6 |pages=76 |doi=10.3389/fnhum.2012.00076 |pmc=3321411 |pmid=22509161 |doi-access=free}}
* {{Cite book |url=https://archive.org/details/theoriesofchildh00moon |title=Theories of Childhood: an Introduction to Dewey, Montessori, Erikson, Piaget & Vygotsky |vauthors=Mooney CG |publisher=Redleaf Press |year=2000 |isbn=978-1-884834-85-1}}
*{{Cite book |title=Advances in Child Development and Behavior Volume 37 |vauthors=Poulin-Dubois D, Brooker I, Chow V |year=2009 |isbn=978-0-12-374470-8 |volume=37 |pages=55–104 |chapter=The developmental origins of naïve psychology in infancy |doi=10.1016/S0065-2407(09)03702-1 |pmid=19673160}}
* {{Cite journal |vauthors=Stiles J, Jernigan TL |date=December 2010 |title=The basics of brain development |journal=Neuropsychology Review |volume=20 |issue=4 |pages=327–348 |doi=10.1007/s11065-010-9148-4 |pmc=2989000 |pmid=21042938}}
* {{Cite journal |vauthors=Tau GZ, Peterson BS |date=January 2010 |title=Normal development of brain circuits |journal=Neuropsychopharmacology |volume=35 |issue=1 |pages=147–168 |doi=10.1038/npp.2009.115 |pmc=3055433 |pmid=19794405}}
* {{Cite journal |vauthors=Vannest J, Karunanayaka PR, Schmithorst VJ, Szaflarski JP, Holland SK |date=May 2009 |title=Language networks in children: evidence from functional MRI studies |journal=AJR. American Journal of Roentgenology |volume=192 |issue=5 |pages=1190–1196 |doi=10.2214/AJR.08.2246 |pmc=2791163 |pmid=19380541}}
{{refend}}

== External links ==
{{Commons category}}
{{Library resources box|onlinebooks=yes}}
* {{Cite web |date=15 February 2022 |title=Child development |url=https://www.cdc.gov/ncbddd/child/ |website=U.S. Centers for Disease Control and Prevention}}
* {{Cite web |title=child development activities for parents |date=3 June 2024 |url=https://www.jointhegrave.com/top-10-child-development-activities-for-parents/}}
* {{Cite web |title=The science of early childhood |url=http://developingchild.harvard.edu/science/ |website=Harvard University Center on the Developing Child}}
* {{Cite web |title=World Association for Infant Mental Health |url=http://www.waimh.org/ |archive-url=https://web.archive.org/web/20090130112913/http://www.waimh.org/ |archive-date=30 January 2009}}

{{Humandevelopment}}
{{Mental and behavioural disorders}}
{{Parenting}}
{{Authority control}}

[[Category:Child development| ]]
[[Category:Developmental psychology]]
[[Category:Childhood|Development]]