In Piaget’s view,
human thought originates in the development of the motor
capacities. Hence babies acquire their earliest
knowledge not only through their perceptions but also through
their actions and the changes that these actions let them
effect in the world.
For example, starting at 2 or 3 months of age, several regions
of the cortex and the cerebellum become
functional. Concomitant progress then appears in the baby’s
posture, eye movements,
and ability to reach and pick up objects.
Between 6 and 12 months, the maturation of the frontal
cortex ensues, along with the gradual appearance
of the abilities to plan, control, and inhibit one’s
of mind refers to the ability to
imagine what other people are thinking, to predict their behaviour
and intentions, to speculate about their concerns and beliefs,
and so on.
From age 3 or 4, when they are very actively acquiring the
structures of language, children are also developing this capability.
At this age, children can infer someone’s reaction to
a situation by imagining themselves in his place, which represents
the prerequisite for empathy.
PIAGET’S MODEL OF COGNITIVE DEVELOPMENT
How does human knowledge
develop? Swiss psychologist Jean Piaget devoted his entire
life to this question. His studies, spread out over nearly
60 years, laid
the foundations for the vast research field of genetic
epistemology, which attempts to understand how our
modes of thinking evolve over the course of our lives.
Trained in biology and philosophy, Piaget drew on concepts
from both these disciplines to study the development of young
children—an ideal setting for observing
thoughts as they are being formed. He concluded very early
on that cognitive development is the product of complex interactions
between the maturation
of the nervous system and that of language, and that
this maturation depends on children’s social and physical
interactions with the world around them.
According to Piaget, it is by acting on their environment that children develop
their first rational constructs. Initially, these cognitive structures,
or thought schemas, as Piaget also called
them, are completely different from an adult’s, but gradually,
they are internalized and become more and more abstract.
Piaget’s theory of cognitive development distinguishes
four primary cognitive structures that correspond to four stages
of development. These
stages are in turn divided
into distinct substages during which specific cognitive abilities emerge.
The first stage of development,
beginning at birth and continuing until about age 2, is the sensorimotor stage.
In this stage, children’s contact with the world around
them depends entirely on the movements that they make and the
sensations that they experience. Whenever they encounter a
new object, they shake it, throw it, or put it in their mouth,
so that they gradually come to understand its characteristics
through trial and error. Around the middle of this stage (about
age 1), children first understand the concept of object permanence—that
an object continues to exist even when it moves beyond their
field of vision.
The second stage is the preoperational stage.
It begins around age 2 and ends around age 6 or 7. During this
stage, which is marked by the acquisition of language, among
other things, children become able to think in symbolic terms,
to form ideas from words and symbols. Children also begin to
understand spatial and numerical concepts and the distinction
between past and future. But they remain highly focused on
the present and on concrete physical situations and have difficulty
in dealing with abstract concepts. Children’s thinking
is also very egocentric at this stage; a child this age often
assumes that other people see situations from his or her viewpoint.
Third comes the concrete
operations stage, from age 6 or 7 to age 11 or 12.
Having absorbed more and more experience of the world, children
now become able to imagine events that occur outside their
own lives. They also begin to conceptualize and to create
sequences of logical reasoning, though this reasoning still
depends on a direct relationship to concrete things. Children
also acquire a certain capacity for abstraction. Hence they
can begin to study disciplines such as mathematics, in which
they can solve problems with numbers and reverse previously
performed operations, but only ones that involve observable
phenomena. At this stage, it is still only the exceptional
child who can solve problems with multiple variables by breaking
them down systematically.
Lastly, what Piaget called
the formal operations stage begins at age
11 or 12. The new capabilities developed in this stage, such
as the abilities to reason hypothetically and deductively and
to establish abstract relationships, are generally mastered
around age 15. By the end of this stage, adolescents, like
adults, can use formal, abstract logic. They can also begin
to think about probabilities and about moral
issues such as justice.
in adapting our thought schemas to new information from the
real world. According to Piaget, this adaptation can occur
in either of two ways: assimilation or accommodation.
Assimilation consists in interpreting
new events in light of pre-existing thought
schemas. For example, a baby knows how to grab
her favourite rattle with the fingers of one
hand, then throw it to hear it make a noise.
When she comes across a new object, such as
her father’s delicate watch, she has
no trouble in transferring this motor schema
that she already knows to this new object and
sending it flying to the ground.
Accommodation is the opposite
process: altering one’s internal
cognitive structures to incorporate a new
object or phenomenon. Suppose this same
baby now encounters a beach ball. At first,
she’ll try to grab it with one hand,
the way she does her rattle. But very quickly,
she’ll realize that this doesn’t
work, and eventually she will discover
how to hold the ball with both hands.
Piaget believed that in the process of understanding the world
around us, we switch back and forth constantly between assimilation
and accommodation. However, during certain periods of development,
we may temporarily rely on one of these modes of adaptation
more than the other.
experiment that Piaget conducted was the “three mountains” experiment.
In this experiment, the child had to decide which of the
first four diagrams in the figure below corresponded to
the view that Piaget had, seated on the opposite side of
the table, as shown in the fifth diagram. Because young
children could not imagine the viewpoint of someone on
the other side of a table, Piaget concluded that they are
incapable of empathy. But in later experiments that gave
children the same age the chance to imagine social situations
rather than spatial ones, the results were quite different.
BEYOND PIAGET’S MODEL
idea that all children go through fixed, sequential
stages of development has been the target of much criticism.
According to Russian psychologist Lev Vygotsky,
the development of human beings is too complex to be defined
by such stages. Vygotsky, and others after him, accorded far
more importance than Piaget did to the social
and environmental influences on cognitive development.
To Piaget, the primary motivation
for the process of human cognitive development came from inside
the individual. His most famous metaphor for describing this
idea was that children are “lone
scientists” who experiment with and explore the world.
In contrast, for Vygotsky, the metaphor that best describes
the primary source of development is that children are “little
apprentices” who receive the help and support that they
need from their teachers in learning situations. Thus, for
Vygotsky, the development of cognition comes more from outside
the individual than from inside.
There is indeed no question that human children are affected
by the cultures
in which they grow up, and even more strongly affected
by their family environments. Children internalize these
social influences through their interactions with the adults
who guide them in their problem-solving efforts.
Contrary to what Piaget posited with
his stages of development, Vygotsky’s followers see
a difference between what children can accomplish on their
own and what they can do with the help of an adult. Vygotsky
used the term “zone of proximal development” to
denote the distance at any given time between what a child
actually knows and what the child can learn under the supervision
of an adult or through contact with other children.
According to Vygotsky, because the
culture (in the large sense) that surrounds a child is thus a
determining factor in that child’s development, if one
studies the development of this child in isolation, as Piaget
does, one cannot adequately represent the process by which children
actually acquire knowledge.
It follows that language is the most effective means that adults
have at their disposal to convey knowledge to children. As learning
language itself becomes a learning tool that they internalize
and use “in their heads ” to think about the world.
Despite the various
criticisms of Piaget’s work, his general principles
are still used as basic references in developing educational
programs for school-age and pre-school-age children. For
example, to help children develop during the sensorimotor
stage, early-childhood educators try to provide rich environments
filled with stimulating objects. In contrast, learning
activities for schoolchildren at the concrete operations
stage must include more problems involving classification
or conservation of physical objects.
Owls locate their
prey through their sense of hearing. Experiments
have shown that the circuits in the owl’s brain that
support this auditory location task are altered by experience.
For instance, if a baby owl is prevented from hearing any
sounds during the critical development period immediately
after it hatches, these circuits will not form correctly,
and the owl will never be able to locate sounds properly.
In mice and rats, the somesthetic maps in
these animals’ brains can be disturbed by abnormal
sensory experiences during a short critical period just following
birth. As regards the olfactory system,
exposure to the mother’s odours during a limited time
period permanently alters the ability of the young of many
species to respond to these smells.
unusual but very well documented case, a mentally disturbed
couple raised their daughter to age 13 while depriving
her almost completely of any exposure to language. Even
though she was subsequently given intensive language training,
she was never able to achieve more than rudimentary communication.
Her difficulties closely parallel those experienced by “wild
children” and confirm the importance of
the critical period for the acquisition of language.
PERIODS IN COGNITIVE DEVELOPMENT
The wide variations
in human personalities and behaviours are the result of
the uniqueness of the brain of every individual. This distinctiveness
develops initially through the first
steps in connecting the brain’s circuits, in
which intrinsic mechanisms lay down the neural pathways
that are the source of a wide range of instinctive behaviours,
for purposes such as seeking food, defending oneself against
enemies, and mating.
But the construction of the nervous system in animals,
including humans, is also influenced by experience. People’s
interactions with the environment produce certain
patterns of neural activity that shape the circuits of the brain. Influences
from the outside world are especially important early in life, during certain
limited time intervals called critical periods.
Critical periods are a general phenomenon that is associated with a number of
different sensory systems. Though the most comprehensive studies have dealt with
the visual systems of mammals (follow the Experiment Module link to the left),
critical periods have also been identified in the development of the auditory,
olfactory, and somesthetic systems (see sidebar).
Some critical periods can be very short—for example,
the critical period for imprinting
in birds. But critical periods for the development of complex behaviours
such as human language can be longer and less sharply defined.
Unlike animals, whose cries of alarm
are inborn, humans need prolonged post-natal experience before
they can produce and decode the sounds that are the basis
for language. Children can learn a language only if they
are exposed to the words of this language during a limited,
critical period before puberty (see sidebar). Similar conditions
of exposure or non-exposure outside this critical period,
later in adult life, will have little effect on language
In addition, the phonetic structure of the particular
language that someone hears during the first few years
of life will permanently affect the way that person perceives
and produces speech.
During the first few months of life, infants do not have any inborn
predispositions for the characteristic phonemes of any particular
language. Hence they can perceive and discriminate all the sounds
of any human language. But eventually, people lose this ability.
For example, adult native speakers of Japanese cannot reliably
distinguish the English “R”and “L” sounds,
probably because this phonetic distinction does not occur in Japanese.
Studies have been conducted to determine up to what age Japanese babies can still
discriminate between these two sounds. In these studies, discrimination was measured
by an increase in the frequency with which the babies engaged in sucking behaviour
or turned their heads away when presented with one of these sounds after they
had habituated to the other. It was found that at 4 months of age, Japanese babies
could distinguish the “R” and “L” sounds just as well
as 4-month-olds who were growing up in English-speaking families. But around
6 months of age, the two sets of babies showed preferences for the phonemes of
their mother tongues. By the time they were 1 year old, the babies no longer
responded at all to the phonetic elements of a language other than their own.
Up to age 7 or 8, however, children can still learn to speak a second language
fluently, with no grammatical errors and no accent, which indicates that the
ability to perceive some phonetic contrasts does last longer than just the first
year of life.