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 intellec-
tual development. Infants in the first couple of years
of life, according to Piaget, are capable only of form-
ing simple schemas based on their actual physical en-
counters 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) re-
flects an ability on the part of the child to form a men-
tal representation of the object and thus allows the
child to be able to think about the object without hav-
ing 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 Pia-
get, children enter the concrete operational period of
development. Now they become capable of perform-
ing simple ‘‘mental operations’’ such as adding, sort-
ing, or ordering objects. They are no longer bound
by their own perceptions of things; rather, they recog-
nize that others have their own perspectives and that
objects have their own constant properties. Neverthe-
less, 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 per-
fect example of a stage theory of development. New
information is being added as children grow and ex-
perience 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 cogni-
tive 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 origi-
nal 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 exam-
ple, contrary to Piaget’s belief, not all preoperational
children are invariably egocentric (i.e., incapable of
taking the perspective of others). Children’s perfor-
mances 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 in-
structions, what experience they have with similar
tasks, etc. Furthermore, it appears that some of Pia-
get’s beliefs about young children’s limited abilities
may have arisen as a function of a limitation of his re-
search methods. As researchers have uncovered in-
creasingly clever and technologically advanced ways
to tap the mental activity of young infants, they have
found that even very young infants understand, re-
member, and can learn far more than Piaget ever re-
alized. 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 develop-
ment, researchers in the field of psychosocial devel-
opment have also developed stage theories toSTAGES OF DEVELOPMENT 383