Stages of Development

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Imagine a playground full of children on a warm summer day. A toddler tentatively makes her way across the sand to retrieve a shovel then, with a smile of triumph, retreats to her mother's side. Nearby a pair of two-year-olds dig in the sand side by side, practically touching yet seemingly unaware of one another. A band of boisterous five-year-olds rush past them, chasing an imagined pirate on a tumultuous sea. A quick survey of these intersecting scenes shows that these groups of children are clearly going about the business of learning and play in very different ways, at increasing levels of sophistication. Over the years, developmental psychologists have confronted the question of how best to characterize these changes in both cognitive and social functioning. Is it a simple matter of children adding to their repertoire of skills and knowledge as they get older (quantitative change), or do higher levels of functioning actually represent a reorganization of the previous level of functioning, much in the way that a caterpillar goes through discrete stages of life on the way to becoming a butterfly (qualitative change)? "Stage models" of development are based on a combination of these two types of conceptualizations. Psychologists have developed such models for understanding and explaining both cognitive and psychosocial development.

Stages of Cognitive Development

Jean Piaget was among the first psychologists to wrestle with the question of how a child develops from simple-thinking newborn to cognitively sophisticated adolescent and adult. Over a lifetime of grappling with this question, he developed a theory of cognitive development in which he identified four major stages or "periods" of development. Underlying this theory are the ideas that each stage of development is a self-contained unit, that each builds upon the preceding stage, that each proceeds from a loosely defined unit into a tightly integrated model, and that children proceed through these stages in a universal, fixed order.

Piaget's stage model centers around the concept of schemas, that is, basic units of knowledge that serve as the building blocks of and framework for intellectual development. Infants in the first couple of years of life, according to Piaget, are capable only of forming simple schemas based on their actual physical encounters with the world: They must experience the world through their senses or motor actions (e.g., touch it, grab it, suck on it, bang it, throw it) in order to know anything about it. Piaget thus termed this the sensorimotor period of development. In the sensori-motor period, schemas are simple. For example, the very young infant develops a sucking schema; that is, the infant organizes information according to what can be sucked (fingers, pacifier, teething ring) and how sucking actions can vary (hard or soft, fast or slow). As the child grows and experiences new things in the world, schemas become more complex.

Perhaps the crowning achievement of the sensori-motor period is the development of the idea that things exist independent of the child, even when the object is out of sight. This amazing new ability is called object permanence. According to Piaget, this knowledge (reflected in the toddler's continued search for an object even after it has been hidden) reflects an ability on the part of the child to form a mental representation of the object and thus allows the child to be able to think about the object without having to experience it via the senses or motor activity.

The ability to form mental representations opens up a whole new world of learning and imagination for children in the preoperational period (roughly from age two to seven years). They engage in pretend play ("there's a monster coming; hide!"); they can role play ("I am the mommy, you are the baby"); they can imagine something even when nothing is there at all (for example, "eating" a seven-course meal off an empty toy dish); they can use one object to stand for another (for example, using a shoe box as a bus). Somewhere around age six or seven, according to Piaget, children enter the concrete operational period of development. Now they become capable of performing simple "mental operations" such as adding, sorting, or ordering objects. They are no longer bound by their own perceptions of things; rather, they recognize that others have their own perspectives and that objects have their own constant properties. Nevertheless, children's ability to perform these operations is limited to real, concrete objects and to the here and now. Once they can apply such operations to abstract concepts and possibilities (usually around age eleven or older), they are said to have reached Piaget's final stage, the formal operational period.

Piaget's theory of cognitive development is a perfect example of a stage theory of development. New information is being added as children grow and experience the world, but there are also qualitative shifts in the way that information is organized to help the child understand the world. Piaget's theory is still the springboard for much of the research on cognitive development that has taken place in the years since his death. Some of this later work, however, has shown that modifications must be made to the original theory.

First, it now seems that the characteristics of the stages that Piaget described are less consistent and less global than he had portrayed. As their ways of thinking mature, children will sometimes show more sophisticated ways of thinking in just one area, or with one type of task, or with one set of objects. For example, contrary to Piaget's belief, not all preoperational children are invariably egocentric (i.e., incapable of taking the perspective of others). Children's performances on some of the classic Piagetian tasks seem to be dependent in part on how familiar the children are with the objects, how well they understand the instructions, what experience they have with similar tasks, etc. Furthermore, it appears that some of Piaget's beliefs about young children's limited abilities may have arisen as a function of a limitation of his research methods. As researchers have uncovered increasingly clever and technologically advanced ways to tap the mental activity of young infants, they have found that even very young infants understand, remember, and can learn far more than Piaget ever realized. In summary, then, psychologists now think of cognitive development as proceeding in terms of gradual changes to higher levels of thinking rather than sudden advances from one style of thinking to another, more sophisticated style.

Stages of Psychosocial Development

Like those who have studied cognitive development, researchers in the field of psychosocial development have also developed stage theories to understand and explain children's development in this domain. By far the most notable and global stage theory of social development comes from the work of Erik Erikson. A psychoanalyst by training, his stage model had roots in Freudian theory but took as its points of departure a lifespan approach to understanding development and a recognition of the impact of culture and society on development.

Erikson characterized social development as proceeding through eight distinct stages that cover the entire lifespan; these stages are summarized briefly in Table 1. Within each stage, a central crisis presents itself. Typically this crisis relates to some important issue confronting the individual at that point of development. Erikson identified a positive and a negative possible outcome for each stage. If development is to proceed favorably, each stage must be resolved in such a way that the positive outweighs the negative. Otherwise, the individual carries the burden of that negatively resolved stage throughout life, constantly facing it but perhaps eventually resolving it in a more favorable direction.

Erikson also recognized that culture and society play an important, ever-expanding role in directing the course of development and determining the outcome of each crisis. At first, the infant's "society" consists primarily of the mother. As the child grows and goes out into the world, however, that circle of influence is expanded to include other adults, peers, and social institutions such as school, churches, and political structures.

In Erikson's theory, the individual is constantly in search of an identity. People seek to define themselves at each stage of development; that definition varies with the stage, but in the best-case scenario there is always a positive "reinvention" of the self such that the person decides that he or she is inherently good, worthy, capable, and lovable. Development in one stage is influenced by the positive or negative outcomes of all the previous stages, much in the same way that Piaget's successive stages of cognitive development were thought to build upon previous stages. Thus, for example, in the scenario where all crises are resolved positively, babies in their first year of life (through experiences with the mother or other primary caretaker) learn to trust that their needs will be met. This gives them the courage and confidence to go out and explore the world once they are able to crawl or walk away from the mother, and to do things for themselves. With support and success in these efforts, by age four or so they develop a desire to go after personal goals, confident that they will succeed in whatever they try. Adolescence marks a special crisis period in Erikson's theory, as this is a time when children face adulthood and seek to define what kind of adult they will be (in Erikson's terms, they face an "identity crisis"). Armed once more with the confidence that they are good, competent, and worthy people, young adults are able to open up their deepest, most vulnerable sides to loved ones, building intimate relationships. They turn their efforts to the good of society, and, in old age, take stock of their lives with satisfaction at their accomplishments and contributions. Thus Erikson's theory, like Piaget's, is a perfect example of a stage model of development. Each stage has its own unique features and issues, yet looking across the stages one can easily trace the impact of previous stages on subsequent development and outcomes.


Returning for a moment to the scene on the playground, Piaget's and Erikson's stage theories help show that children at these various ages are not simply just adding to their experience and knowledge base as they grow older in the way that a person glides up an escalator at a smooth and steady pace. Instead, their development is more like walking up a grand staircase with multiple plateaus. Within a level they are always making advances, and those advances taken together help prepare them for the next level. Once they reach that next higher level, they are facing a new set of issues, perhaps functioning in a qualitatively different way, but building nevertheless upon their rich experience of previous levels.



Erikson, Erik H. Identity: Youth and Crisis. New York: Norton, 1968.

Ginsburg, Herbert, and Sylvia Opper. Piaget's Theory of Intellectual Development, 3rd edition. Englewood Cliffs, NJ: Prentice-Hall, 1988.

Gross, Francis L. Introducing Erik Erikson: An Invitation to His Thinking. Lanham, MD: University Press of America, 1986.

Miller, Patricia H. Theories of Developmental Psychology, 3rd edition. New York: Freeman, 1993.

Piaget, Jean, and Bärbel Inhelder. The Psychology of the Child. New York: Basic, 1969.

Siegler, Robert S. "Children's Thinking: How Does Change Occur?" In Franz E. Weinert and Wolfgang Schneider eds., Memory Performance and Competencies: Issues in Growth and Development. Hillsdale, NJ: Lawrence Erlbaum, 1995.

Virginia D.Allhusen