The Growth of Thought:
Cognitive Development
earned a doctorate in natural science and published a
novel, Piaget’s interest turned to psychology. He met
Theodore Simon, who had collaborated with Alfred
Binet in devising the first useful intelligence tests (see
Cognitive development refers to transitions in
Chapter 9). Working in Simon’s Paris laboratory, Piayoungsters’ patterns of thinking, including reaget administered intelligence tests to many children
soning, remembering, and problem solving. The
to develop better test norms. In doing this testing,
investigation of cognitive development was dominatPiaget became intrigued by the reasoning underlying
ed in most of the second half of the 20th century by
the children’s wrong answers. He decided that measthe theory of Jean Piaget (Kessen, 1996). Much of
uring children’s intelligence was less interesting than
our discussion of cognitive development is devoted
studying how children use their intelligence. In 1921
to Piaget’s theory and the research it generated, alhe moved to Geneva, where he spent the rest of his
though we’ll also delve into other approaches to coglife studying cognitive development. Many of his
nitive development.
ideas were based on insights gleaned from careful observations of his own three children during their inOverview of Piaget’s Stage Theory
fancy.
Jean Piaget (1929, 1952, 1983) was an interdiscipliLike Erikson’s theory, Piaget’s model is a stage thenary scholar whose own cognitive development was ory of development. Piaget proposed that youngsters
exceptionally rapid. In his early 20s, after he had progress through four major stages of cognitive development, which are characterized by fundamentally
different thought processes: (1) the sensorimotor period (birth to age 2), (2) the preoperational period
Figure 11.11
(ages 2 to 7), (3) the concrete operational period (ages
Piaget’s stage theory. Piaget’s theory of cognitive
7 to 11), and (4) the formal operational period (age
development identifies four stages marked by funda11 onward). Figure 11.11 provides an overview of
mentally different modes of thinking through which
each of these periods. Piaget regarded his age norms
youngsters evolve. The approximate age norms and
as approximations and acknowledged that transitional
some key characteristics of thought at each stage are
summarized here.
ages may vary, but he was convinced that all children
progress through the stages
Stage 4
of cognitive development in
Stage 3
the same order.
Noting that children acStage 2
Formal
Stage 1
operational
tively explore the world
Stage 1
Stage 2
Concrete
period
around them, Piaget asserted
operational
Preoperational
period
that interaction with the enSensorimotor
period
vironment and maturation
period
gradually alter the way chilMental
operations
Mental
operations
Coordination of
Development of
dren think. According to Piaapplied
to
abstract
applied
to
concrete
sensory input
symbolic thought
get, children progress in their
ideas;
logical,
events; mastery
and motor
marked by
thinking through the comsystematic thinking
of conservation,
responses;
irreversibility,
plementary processes of ashierarchical
development of
centration,
classification
object permanence
and egocentrism
similation and accommodation. Assimilation involves
interpreting new experienBirth to 2 years
2 to 7 years
7 to 11 years
Age 11 through
ces in terms of existing
adulthood
mental structures without
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changing them. In contrast, accommodation involves changing existing mental structures to explain new experiences. Accommodation and assimilation often occur interactively. For instance, a child
who has learned to call four-legged pets “puppies”
may apply this scheme the first time she encounters a
cat (assimilation), but she will eventually discover that
puppies and cats are different types of animals and
make adjustments to her mental scheme (accommodation). With the companion processes of assimilation and accommodation in mind, let’s turn now to
the four stages in Piaget’s theory.
Sensorimotor Period. One of Piaget’s foremost
contributions was to greatly enhance our understanding of mental development in the earliest months of
life. The first stage in his theory is the sensorimotor period, which lasts from birth to about age 2. Piaget
called this stage sensorimotor because infants are developing the ability to coordinate their sensory input
with their motor actions.
The major development during the sensorimotor
stage is the gradual appearance of symbolic thought.
At the beginning of this stage, a child’s behavior is
dominated by innate reflexes. But by the end of the
stage, the child can use mental symbols to represent
objects (for example, a mental image of a favorite
toy). The key to this transition is the acquisition of
the concept of object permanence.
Object permanence develops when a child recogFigure 11.12
nizes that objects continue to exist even when
Piaget’s conservation task. they are no longer visible. Although you surely take
After watching the transforma- the permanence of objects for granted, infants aren’t
tion shown, a preoperational
aware of this permanence at first. If you show a 4child will usually answer that
month-old an eye-catching toy and then cover the
the taller beaker contains
toy with a pillow, the child will not attempt to search
more water. In contrast, the
for the toy. Piaget inferred from this observation that
child in the concrete operthe child does not understand that the toy continues
ational period tends to reto exist under the pillow. The notion of object perspond correctly, recognizing
manence does not dawn on children overnight. The
that the amount of water in
first signs of this insight usually appear between 4 and
beaker C remains the same
as the amount in beaker A.
8 months of age, when children will often pursue an
Step 1
The child agrees that
beakers A and B contain
the same amount of
water.
A
Step 3
The child is asked:
“Do beakers A and C
contain the same
amount of water?”
B
B
Step 2
The child observes
as the water from
beaker B is poured
into beaker C,
which is shaped
differently.
C
A
C
object that is partially covered in their presence.
Progress is gradual, and Piaget believed that children
typically don’t master the concept of object permanence until they’re about 18 months old.
Preoperational Period. During the preoperational period, which extends roughly from age 2 to age 7,
children gradually improve in their use of mental images. Although progress in symbolic thought continues, Piaget emphasized the shortcomings in preoperational thought.
Consider a simple problem that Piaget presented
to youngsters. He would take two identical beakers
and fill each with the same amount of water. After a
child had agreed that the two beakers contained the
same amount of water, he would pour the water
from one of the beakers into a much taller and thinner beaker (see Figure 11.12). He would then ask
the child whether the two differently shaped beakers
still contained the same amount of water. Confronted with a problem like this, children in the preoperational period generally said no. They typically
focused on the higher water line in the taller beaker
and insisted that there was more water in the slender beaker. They had not yet mastered the principle
of conservation. Conservation is Piaget’s term for
the awareness that physical quantities remain
constant in spite of changes in their shape or
appearance.
Why are preoperational children unable to solve
conservation problems? According to Piaget, their
inability to understand conservation is due to some
basic flaws in preoperational thinking. These flaws include centration, irreversibility, and egocentrism.
Centration is the tendency to focus on just one
feature of a problem, neglecting other important
aspects. When working on the conservation problem
with water, preoperational children tend to concentrate on the height of the water while ignoring the
width. They have difficulty focusing on several aspects of a problem at once.
Irreversibility is the inability to envision reversing an action. Preoperational children can’t mentally
“undo” something. For instance, in grappling with
the conservation of water, they don’t think about
what would happen if the water were poured back
from the tall beaker into the original beaker.
Egocentrism in thinking is characterized by a
limited ability to share another person’s viewpoint. Indeed, Piaget felt that preoperational children fail to appreciate that there are points of view
other than their own. For instance, if you ask a preoperation girl whether her sister has a sister, she’ll
probably say no if they are the only two girls in the
family. She’s unable to view sisterhood from her sister’s perspective (this also shows irreversibility).
A notable feature of egocentrism is animism—the
belief that all things are living, just like oneself.
Thus, youngsters attribute lifelike, human qualities to
inanimate objects, asking questions such as, “When
does the ocean stop to rest?” or “Why does the wind
get so mad?”
As you can see, Piaget emphasized the weaknesses
apparent in preoperational thought. Indeed, that is
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why he called this stage preoperational. The ability to
perform operations—internal transformations, manipulations, and reorganizations of mental structures—emerges in the next stage.
children can’t handle hierarchical classification problems that require them to focus simultaneously on
two levels of classification. However, the child who
has advanced to the concrete operational stage is not
as limited by centration and can work successfully
Concrete Operational Period. The development of with hierarchical classification problems.
mental operations marks the beginning of the concrete operational period, which usually lasts from Formal Operational Period. The final stage in Piaabout age 7 to age 11. Piaget called this stage con- get’s theory is the formal operational period, which
crete operations because children can perform opera- typically begins around 11 years of age. In this stage,
tions only on images of tangible objects and actual children begin to apply their operations to abstract
events.
concepts in addition to concrete objects. Indeed,
Among the operations that children master during during this stage, youngsters come to enjoy the heady
this stage are reversibility and decentration. Reversi- contemplation of abstract concepts. Many adolesbility permits a child to mentally undo an action. De- cents spend hours mulling over hypothetical possibilicentration allows the child to focus on more than one ties related to abstractions such as justice, love, and
feature of a problem simultaneously. The new found free will.
ability to coordinate several aspects of a problem
According to Piaget, youngsters graduate to relahelps the child appreciate that there are several ways tively adult modes of thinking in the formal operato look at things. This ability in turn leads to a de- tions stage. He did not mean to suggest that no furcline in egocentrism and gradual mastery of conserva- ther cognitive development occurs once children
tion as it applies to liquid, mass, number, volume, reach this stage. However, he believed that after chilarea, and length (see Figure 11.13 on the next page). dren achieve formal operations, further developments
As children master concrete operations, they de- in thinking are changes in degree rather than fundavelop a variety of new problem-solving capacities. mental changes in the nature of thinking.
Let’s examine another problem studied by Piaget.
Adolescents in the formal operational period beGive a preoperational child seven carnations and come more systematic in their problem-solving efthree daisies. Tell the child the names for the two forts. Children in earlier developmental stages tend
types of flowers and ask the child to sort them into to attack problems quickly, with a trial-and-error apcarnations and daisies. That should be no problem. proach. In contrast, children who have achieved forNow ask the child whether there are more carnations mal operations are more likely to think things
or more daisies. Most children will correctly respond through. They envision possible courses of action and
that there are more carnations. Now ask the child try to use logic to reason out the likely consequences
whether there are more carnations or more flowers. of each possible solution before they act. Thus,
At this point, most preoperational children will thought processes in the formal operational period
stumble and respond incorrectly that there are more can be characterized as abstract, systematic, logical,
carnations than flowers. Generally, preoperational and reflective.
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