Understanding how children develop can help parents raise their children more effectively, lead society as a whole to adopt wiser policies regarding children’s welfare, and answer intriguing questions about human nature. Children are influenced by their early experiences, but some are able to overcome even the most traumatic backgrounds. Child development research is important for a number of reasons. First is to gain information and understanding that can help parents raise their own children successfully. Second is to gain insight into social policy issues related to children and to help society adopt policies that promote children’s well-being. Thirdly, is to better understand human nature in general.

Historical Foundations in the Study of Child Development

Some of the earliest recorded ideas about children’s development were those of Plato and Aristotle. These two Greek philosophers, who lived in the fourth century b.c., were particularly interested in how children’s nature and the nurture they receive influenced development. Both Plato and Aristotle believed that the long-term welfare of society depended on children being raised properly. Careful upbringing was essential, because children’s nature would otherwise lead to their becoming rebellious and unruly. Plato emphasized self-control and discipline as the most important goals of education. Aristotle agreed with Plato that discipline was necessary, but he was more concerned with fitting child rearing to the needs of the individual child. Plato believed children are born with innate knowledge, while Aristotle believed that all knowledge comes from experience and that without experience, the mind is merely a potential.

Roughly 2,000 years later, the English philosopher John Locke and French philosopher Jean-Jacques Rousseau proposed ideas that were related to, but also somewhat different from, those of Plato and Aristotle regarding how parents and the general society can best promote child development. Locke, like Aristotle, viewed the child as a tabula rasa, or blank slate, where development largely reflects the nurture provided by the child’s parents and the broader society. He believed that the most important goal of child rearing is the growth of character.

Whereas Locke advocated first instilling discipline and then progressively increasing the child’s freedom, Rousseau believed that parents and society should give children maximum freedom from the beginning. Rousseau claimed that children learn primarily from their own spontaneous interactions with objects and other people, rather than through instruction by parents or teachers. He even argued that children should not receive any formal education until the age of 12 when they reach “the age of reason” and can judge for themselves the worth of what they read and are told. Before then, they should be allowed the freedom to explore whatever interests them. Although these philosophical views raised fundamental questions, they were based more on impressions and general beliefs than on systemic observations that could reveal how children actually develop.

Beginning Research on Children

A research-based approach to understanding child development began to emerge in the nineteenth century, in part as a result of two converging forces: social reform movements and Charles Darwin’s theory of evolution.

During the Industrial Revolution, many children in Europe and the United States (U.S.) worked as paid laborers. Some were as young as 5 or 6 years old, and spent as much as twelve hours a day working in factories or mines, often in extremely hazardous conditions. These harsh circumstances concerned a number of social reformers, who began to study the effects of the conditions on the children’s development. In addition to the first child labor laws, these and other child social reform movements established a legacy of research conducted for the benefit of children and provided some of the earliest descriptions of the adverse effects that harsh environments can have on children’s development.

Later in the nineteenth century, Charles Darwin’s work on biological evolution inspired a number of scientists to propose that intensive study of child development might lead to important insights into the nature of the human species. Darwin himself was interested in child development and in 1877 published an article titled “A Biographical Sketch of an Infant,” which presented his careful observations of the motor, sensory, and emotional growth of his own infant son. Darwin’s “baby biography”—a systematic description of day-to-day development—represented one of the earliest methods for studying children.

Emergence of Child Development as a Discipline

In the late nineteenth and early twentieth centuries, child development began to emerge as a formal field of inquiry. A number of universities established departments of child development, and the first professional journals devoted to the study of child development were founded. Also emerging during this period were the first theories of child development to incorporate important research findings. One prominent theory, that of Sigmund Freud, was based in large part on results from experiments with hypnosis and analysis of patients’ recollections of their dreams and childhood experiences. On the basis of this evidence, Freud concluded that biological drives, especially sexual ones, were a crucial influence on development. Another prominent theory was that of James Watson, which was based on the results of experiments examining the effects of reward and punishment on the behavior of rats and other animals. Watson concluded that children’s development is controlled by environmental conditions, especially the rewards and punishments that follow particular behaviors.

Enduring Themes in Child Development

The modern study of child development has resulted in the establishment of particular themes, which help us to answer some fundamental questions about children. The first is whether nature and nurture coexist in the development of children. Nature refers to the biological component inherent in each individual. This genetic inheritance influences everything from our physical appearance, personality, intellectual ability, and mental health to certain preferences. Nurture refers to the environment, both social and physical, that influence development, including the womb from which the child spent the prenatal period to where the child grows up, what schools the child will attend, and what friends the child will have and interact with.

Today developmentalists recognize the interaction between nature and nurture. Rather than asking which is more important, developmentalists ask how nature and nurture work together to shape development. One of the main lessons of research on the nature-nurture interaction is that the timing of experiences is often crucial. For example, the timing of puberty influences girls’ reactions to junior high school. Many other instances where the timing of experience is critical occur in the first year or so after birth. In particular, if highly abnormal experiences occur early in life, they often have especially serious and lasting deleterious effects on development.

A second theme is the active child. With all the attention paid to the role of nature and nurture in development, what is often overlooked are the ways in which children contribute to their own development. Even in infancy and early childhood, this contribution is reflected in many ways. Three important contributions occur during the child’s first years: attentional patterns, their use of language, and their play.

Children first begin to shape their own development through the selection of what to pay attention to. Even newborns look towards objects that make noise and move. This preference helps them to learn about important parts of the world, such as people and other animals. Once they begin speak, usually around 9 to 15 months, development of their mental activity becomes evident in their use of language. For example, toddlers often talk when they are alone in the room and no one else is present to reward them or react to what they are saying. Only if children were internally motivated to learn language would they practice talking under these circumstances.

Children’s play also provides many examples of how their internally motivated activity contributes to their development. Children play by themselves for the sheer joy of doing so, but they also learn a great deal in the process. Children’s active contribution to their own development is also evident in particular activities Around the age of 2, children sometimes engage in socio-dramatic play, an activity in which they pretend to be different people in make-believe situations. In addition to being inherently enjoyable, these make-believe games teach children valuable lessons, such as how to cope with fears. Children’s contributions to their own development increase as they grow older. When they are young, their parents are important determinants of their children’s environments. In contrast, older children and adolzescents choose many environments, friends, and activities for themselves. These choices exert a huge impact on their future.

A third theme is whether development is continuous or discontinuous. Some scientists envision children’s development as a continuous process of small, incremental changes. Others believe that the process is a series of sudden, discontinuous changes. Researchers who view development as discontinuous start from a common observation: children of different ages seen qualitatively different. A 4-year-old and a 6-year-old child, for example, seem to differ not just in how much they know but also in the way they view the world.

A common approach in understanding age-related differences among children comes from stage theories, that propose that development occurs in a progression of distinct age-related stages. According to these theories, a child’s entry into a new stage involves relatively sudden, qualitative changes from one coherent way of experiencing the world to a different coherent way of experiencing it. One of the most well-known stage theorists is that of Jean Piaget. Piaget’s theory of cognitive development holds that between birth and adolescence, children go through four stages, each characterized by distinct intellectual abilities and ways of understanding and reasoning about the world. Other theories include Sigmund Freud’s theory of psychosexual development, Erik Erikson’s theory of psychosocial development, and Lawrence Kohlberg’s theory of moral development. Each of these stage theories propose that children of a given age show broad similarities across many situations and that their behaviors differ sharply at different ages.

Even though these stage theories have been very influential, in the past 20 years, researchers have concluded that in most aspects of development, changes are gradual instead of sudden, and that development occurs skill by skill, and task by task, instead of in a broadly unified way. This view of development is less dramatic, but a great deal of evidence supports it. One such piece of evidence is the fact that a child often will behave in accord with one stage on one task but in accord with a difference stage on another task. This variable level of reasoning makes it difficult to view the child as being “in” a particular stage.

A fourth theme is the mechanisms with which change occurs. A useful framework in trying to understand this particular theme is Darwin’s theory of evolution. According to evolutionary theory, species originate and change through two main processes: variation and selection. Variation refers to the differences within and among individuals. Selection involves the more frequent survival, and therefore the greater reproduction, of organisms that are well adapted to their environment. Through the joint operation of variation and selection, species that are better adapted to a given environment become more prevalent in that environment over time, while less well adapted species become rarer or disappear altogether.

From a psychological viewpoint, variation and selection appear to produce changes within an individual’s lifetime. Psychological variation involves the diverse ways in which people think, act, and relate to each other. Psychological selection includes increasing reliance, with age and experience, on the most useful of these ways of thinking, acting, and relating. Together, such variation and selection seem to produce a wide variety of positive changes in psychological functioning.

In biological evolution, the organisms that are best adapted to the environment tend to increase in number over time. Similarly with cognitive development, the most efficient strategies increase in use as children increase in age and experience. Thus, as children generate the correct answer to a problem increasingly often, they come to associate the answer with the problem, which allows them to retrieve it from memory more often. Evolutionary accounts have proved useful for understanding development in many areas beyond arithmetic. These include development of social relationships, sex differences, language, and sports. New variations in these areas emerge out of the universal tendency for children to play and explore their environments. Selection occurs through children’s increasing use of those variations that allow them to meet their goals consistently, quickly, and easily.

The fifth theme is how sociocultural context plays a role in child development. Children grow up in a particular set of physical and social environments, in a particular culture, under particular economic circumstances, at a particular point in history. These make up the physical, social, cultural, economic, and historical circumstances that constitute the sociocultural context of a child’s life. The most obviously important parts of children’s sociocultural contexts are the people with whom they interact (e.g., parents, grandparents, relatives, siblings, day-care workers, friends, peers) and the physical environment in which they live (e.g., their home, day-care center, school, neighborhood). Another important but less tangible part of the sociocultural context concerns the institutions that influence children’s lives (e.g., school systems, religious institutions, sports leagues). Yet another important set of influences include the general characteristics of the child’s society (e.g., its wealth and technological advancements, values, beliefs, attitudes, traditions; laws and political structures).

One method that developmentalists use to understand the influence of the sociocultural context is to compare the lives of children who grow up in different cultures. Such comparisons often reveal that practices one culture takes for granted and views as “natural” may be different from other cultures. Contexts of development differ not just between cultures but within cultures as well. In multicultural societies, many contextual differences are related to ethnicity, race, socioeconomic status (a measure of social class based on income and education). Virtually all aspects of children’s lives, from the food they eat to the parental discipline they receive to the games they play, are influenced by these characteristics.

The sixth theme is individual differences between children. Anyone who has had experience with children appreciates their uniqueness- their differences not only in physical appearance but everything from activity level and temperament to intelligence and emotionality. These differences among children emerge very quickly. There are four factors that have been identified that could contribute to the differences among children within and among families. These factors include genetic differences, differences in treatment by parents and others, differing effects on children of similar experiences, and children’s choices of environments.

A final theme is how research can promote children’s well-being. Improved understanding of child development often leads to practical benefits. Several examples include programs for helping children cope with anger or recommendations regarding how to obtain valid eyewitness testimony from young children. Another type of benefit that child development research has yielded is procedures for diagnosing developmental disorders early, when they can be corrected most easily and completely. Another valuable application of child development research has been programs for helping children learn more effectively. Not only are these programs beneficial in trying to prevent later problems, but they are also intervention-focused in helping children overcome these problems and difficulties.

Jean Piaget’s Theory of Cognitive Development

As mentioned earlier, Jean Piaget is one of the most influential theorists within child development research. Piaget’s theory has withstood the test of time because his observations and descriptions of children vividly convey the flavor of their thinking at different ages. Another reason is the exceptional breadth of his theory. A third reason is the thought-provoking observations Piaget used to support the theory. Finally, another reason is the theory’s intuitively plausible depiction of the interaction of nature and nurture and the recognition of both continuities and discontinuities in development.

Piaget’s fundamental suggestion about children was that from birth onward they are active mentally as well as physically, with their activity greatly contributing to their own development. His approach is often labeled constructivist, because it depicts children constructing knowledge for themselves in response to their experiences. The “child scientist” is the dominant metaphor in Piaget’s theory. He believed that nature and nurture work in conjunction to produce cognitive development. Nurture includes every kind of experience the child encounters, and nature includes the child’s maturing brain and body; his ability to perceive, act, and think; and motivation to meet two basic functions that are central to cognitive growth: adaptation and organization. Adaptation is the tendency to respond to the demands of the environment in ways that meets one’s goals. Organization is the tendency to integrate particular observations into coherent knowledge.

Piaget depicted development as involving both continuities and discontinuities. The main sources of continuity include assimilation, accommodation, and equilibrium that work together from birth to propel development onward. Assimilation is the process by which people translate incoming information into a form that they can understand. Accommodation is the process by which people adapt current knowledge structures in response to new experiences. Finally, equilibrium is the process by which children, and others, balance assimilation and accommodation to create a stable, coherent understanding of the world. First, children are satisfied with their understanding of a phenomenon (equilibrium). Then, children perceive that their understanding is inadequate (disequilibrium), because they recognize shortcomings in their understanding but cannot generate a superior alternative. Finally, they develop a more sophisticated understanding that eliminates the shortcomings of the old one. This new understanding provides a more stable equilibrium.

Although Piaget placed some emphasis on continuous aspects of cognitive development, the most famous part of his theory concerns discontinuous aspects, the distinct stages of cognitive development. Piaget viewed these stages as products of the basic human tendency to organize knowledge into structures. The central proponents of Piaget’s stage theory include the following: qualitative change, broad applicability, brief transitions and invariant sequences. Piaget believed that children of different ages think in qualitatively different ways. The type of thinking characterized by each stage pervades a child’s thinking across diverse topics and contexts. Children do not move from one stage to the next quickly and easily. Instead, they pass through a brief transitional period in which they fluctuate between the type of thinking characteristic of the new, more advanced stage and that of the old, less advanced one. Individuals everywhere and in various historical periods progress through the stages in the same order; no stage is skipped.

Piaget hypothesized that children go through four stages of cognitive development: sensorimotor, preoperational, concrete operational, and formal operational. The sensorimotor stage is between birth and 2 years. During this period, the infant’s intelligence develops and is expressed, through sensory and motor abilities. Through the maturation of their sensorimotor abilities and the application of these learning mechanisms to their experiences, infants learn about people and objects and construct rudimentary forms of fundamental concepts such as time, space, and causality. Throughout this period, they live largely in the here and now: their intelligence is bound to their immediate perceptions and actions.

In the preoperational stage, between the ages of 2 and 7, toddlers and preschoolers become able to represent their experiences in language, mental imagery, and symbolic thought. This allows them to remember their experiences for longer periods of time and to form more sophisticated concepts. However, Piaget viewed children at this stage as unable to perform operations, or reversible mental activities. The inability to perform such operations results in young children having difficulty thinking in consistent, logical ways. Instead, they focus on single, perceptually striking aspects of an event or problem, even when multiple aspects are important.

In the concrete operational stage, between ages 7 and 12 years of age, children can reason logically about concrete objects and events. However, they have difficulty thinking in purely abstract terms and in combining information systematically. The final stage of cognitive development is the formal operational stage, ages 12 and beyond, children can think about concrete events but also about abstractions and purely hypothetical situations. They can also perform systematic scientific experiments and draw appropriate conclusions from them.

Information-Process Theories

Information-process theorists view children as undergoing continuous cognitive change. Important changes are viewed as occurring constantly, rather than being restricted to special transition periods between ages. Cognitive growth is viewed as typically occurring in small increments rather than abruptly. This depiction differs from Piaget’s belief that children progress through qualitatively different stages separated only by relatively brief transition periods. Also basic to information-processing theories is the assumption that children are active problem-solvers. Problem-solving involves a goal, a perceived obstacle, and a strategy or rule for overcoming the obstacle and attaining the goal. Two key cognitive processes that are emphasized in information-processing analyses of children’s problem solving are planning and analogical reasoning.

Analysis of the information-processing requirements of planning indicates that it requires a kind of strategy choice, in which the individual decides to forgo immediate attempts to solve the problem in favor of analyzing which strategy is likely to be most effective. Within this perspective, several factors seem likely to lead children, especially young ones, to choose not to plan even when doing so would help them solve problems. Planning requires children to inhibit their desire to move directly toward the goal. A large part is due to the maturation of the frontal lobe, which plays an important role in inhibition, and has not matured yet. Young children tend to be overly optimistic. They think they can remember more, communicate more effectively, and imitate a model more accurately than they actually can. Plans can fail, either because they were inherently flawed or because they were badly executed. This high failure rate makes planning a less attractive option than if planning were consistently successful. It is important to note that brain maturation, in combination with experiences that reduce over-optimism and demonstrate the value of planning, leads to an increase in frequency and quality of planning well into adolescence.

People often understand new problems in terms of familiar ones. Successful analogical reasoning requires ignoring superficial dissimilarities and focusing on underlying parallel relationships. As with planning, a rudimentary form of analogical reasoning emerges around children’s first birthday. This early competence, however, is initially limited to situations in which the new problem closely resembles the old. Superficial similarity between the original and new problems continues to influence analogical reasoning well beyond infancy. Even in middle childhood, younger children often require more surface similarity to draw an analogy than do older ones.

Core-Knowledge Theories

The core-knowledge theory reflects two features in research. The first is the focus on particular areas such as understanding of other people, that have been important throughout human evolutionary history. Other key areas viewed as core knowledge include recognizing the difference between living and nonliving things, identifying human faces, finding one’s way around the environment, and learning language.

A second feature of the core-knowledge approach is the assumption that in certain areas of probable importance in human evolution, young children reason in ways that are considerably more advanced than Piaget’s theory suggested were possible. If children under the age of 6 or 7 were completely egocentric, they would assume that other people’s knowledge is the same as their own. From this perspective, there would be no point to making a false statement because the other person would know it was false. But studies of young children’s deceptions indicate that 3-year-olds understand that other people can be fooled. The question is how children come to have such sophisticated knowledge so early in life.

Core-knowledge theories depict children as active learners, constantly striving to solve problems and to organize their understanding into coherent wholes. In this aspect, these theories’ perspective on children’s nature resembles those of Piagetian and information-processing theories.

The way in which core-knowledge theories differ strongly from Piagetian and information-processing theories is in their view of children’s innate capabilities. Piaget and information-processing theorists believe that children enter the world equipped only with general learning abilities and that they must actively apply these abilities to gradually increase their understanding of all types of content. In contrast, core-knowledge theorists view children as entering the world not only with general learning abilities but also with specialized learning abilities that allow them to quickly and effortlessly acquire information of evolutionary importance. Where the central metaphors within Piagetian and information-processing theories are the child as scientist and the child as computational system the central metaphor in the core-knowledge approach is the child as well-equipped product of evolution.

Sociocultural Theories

Sociocultural approaches emphasize that much of development takes place through direct interactions between children and other people. Rather than viewing children as individuals trying to make sense of the world through their own efforts, sociocultural theorists view children as social beings, enmeshed in the lives of other people who want to help them acquire the skills and knowledge valued by their culture.

A major player among the sociocultural theorists was Russian psychologist Lev Vygotsky. He portrayed children as social beings, intertwined with other people who are eager to help them gain skills and understanding. Vygotsky viewed them as intent on participating in activities that happen to be prevalent in their local settings. Whereas Piaget emphasized qualitative changes in thinking, Vygotsky emphasized continuous, quantitative changes.

Among the important aspects of Vygotsky’s legacy is the idea that cognitive change originates in social interaction. Vygotsky and contemporary sociocultural theorists have proposed a number of more specific ideas about how change occurs. One of these ideas is guided participation, in which more knowledgeable individuals organize activities in ways that allow less knowledgeable people to engage in them at a higher level than they could manage on their own. Three other related concepts include: intersubjectivity, social scaffolding, and the zone of proximal development.

Sociocultural theorists believe that the foundation of human cognitive development is our ability to establish intersubjectivity, the mutual understanding that people share during communication. Effective communication requires participants to focus on the same topic and on each other’s reaction to whatever is being communicated.

Children’s learning is also aided by social scaffolding, in which more competent people provide a temporary framework that supports children’s thinking at a higher level than children could manage on their own. Ideally, this framework includes explaining the goal of a task, demonstrating how the task should be performed, and helping the child execute the most difficult parts. This is, in fact, the way parents tend to teach their children. Through the process of social scaffolding, children become capable of working at a higher level than if they had not received such help. At first, this higher-level functioning requires extensive support, then it requires less support, and eventually it becomes possible without any support. The higher the quality of scaffolding, the greater the child’s learning.

In analyzing the process of social scaffolding, Vygotsky used the term zone of proximal development (ZPD) to refer to the range of performance between what children can do unsupported and what they can do with optimal support. Implicit in this label is the idea that development is most likely when a child’s thinking is supported by a more knowledgeable person at a somewhat higher level than the child can manage, but no so far beyond the unaided level that the child would be lost.

See also: Childhood depression ; Early childhood education ; Emotional intelligence ; Parent attachment ; Sociocultural factors