In reading books about
Piaget’s theory of stages of development, one often
gets the impression that the formal operations stage is the
final stage of thinking, and that everyone ends up reaching
it. But that is not the case. Piaget himself came to this
conclusion when he observed in the early 1970s that a significant
percentage of adults could not solve certain problems specific
to the formal operations stage, such as the pendulum problem
discussed elsewhere on this page.
As for the idea that no one can go further than the formal
operations stage, nothing could be less certain. For Piaget,
there were no limits to human development. Hence he even posited “post-formal
operations” stages or “operations to the nth power” stages
that might be reached by professional mathematicians or specialists
in other fields involving a high degree of abstraction.
A similar succession
of stages is observed in postural and motor development:
babies learn first how to hold their heads up, then how to
sit upright, then how to stand, and finally how to walk.
In 1946, Arnold Gesell showed that this succession proceeded
from the top of the body downward (cephalo-caudally) and, for
each arm or leg, from the segments closest to the trunk outward
Gesell also pointed out that this phenomenon was progressive,
because each stage involved an increase in the control of muscle
tonus and in the co-ordination
of movements, both of which were made possible by the maturation
of the nervous system.
is through action that the newborn constructs its body schema.
When its hand touches its foot, the two sensations, one in
the hand and the other in the foot, turn inward onto its
own body, whereas if the infant touches its bib, or its mother’s
breast, then the sensation in its hand opens onto the outside
world. It takes the infant 18 months to two years to realize
that it is separate from the world surrounding it, that it
will be alone in its skin until the day it dies.”
- Henri Laborit, La légende des comportements, p.93
Piaget used the term “constructivism” to describe his
approach, because he believed that the acquisition of knowledge
is a lifelong process of continuous self-construction. He also
spoke of “interactionism” to stress the constant
interaction between heredity and environment in developmental
processes. All of this seems obvious to us today. But for a large
part of Piaget’s career, his approach was taken less seriously
than approaches such as Arnold Gesell’s, which basically
emphasized genetic maturation as the source of child development,
or, conversely, purely behaviourist approaches such as B.F. Skinner’s.
To Piaget, knowledge is nothing more and nothing less than a biological
function that takes the form of a distinctive cognitive structure
in every individual. This structure emerges from the individual’s
actions and develops both by assimilating new
information into schemas that are already part of it and by accommodating (adapting)
to new information that does not fit into it in its current form.
In popular culture, Piaget is known mainly
for his model of stages of development, but it is this concept
of the cognitive structure that is at the heart of Piagetian theory.
major stages of development that he described were for him
nothing more than guideposts for following the process of cognitive
development in children. Moreover, in Piaget’s view, other
major stages beyond these four were possible, and every stage could
be divided into substages.
In the first stage following birth, the sensorimotor
stage, thought develops through action. This stage is
divided into several substages. Substage 1— innate reflexes—occurs
during the first month of life, and involves reflex actions such
as sucking, crying, coughing, wriggling, urinating, and defecating.
Substage 2—primary circular reactions—lasts until
about 4 months of age. In substage 2, babies tirelessly repeat
actions that give them pleasure, such as sucking their thumbs.
Next comes the period when babies discover that they are separate
from the outside world. They begin to repeat actions that that
gave them some kind of satisfaction when they first performed
them at random. Around 1 year of age, children become aware of
cause-and-effect relationships and the permanence of objects—if
an object is removed from their field of vision, they will start
looking for it immediately. Between 1 and 2 years, children begin
actively seeking novelty through experimentation. For example,
a child might bang on various objects with his spoon to try to
get different sounds out of them. As they approach age 2, children
clearly develop mental representations that let them, for example,
imitate a gesture that they see someone else make, draw simple
empirical conclusions, pretend that a given object is really
something else, and so on.
By presenting certain concrete problems
and questioning children about them, Piaget was able to determine
whether a given skill was attained within a given stage of
development. For example, in the problem illustrated here,
he might pour the liquid from the low, wide container on the
left into the tall, narrow one on the right, then ask the child
whether the amount of liquid in the second container was the
same or different. A child in the preoperational stage (age
2 to about 6 or 7) would say that there was more liquid in
the second container, because the level of the liquid was higher.
But a child in the concrete operations stage (beginning around
6 or 7) would know that, despite appearances, the same volume
of liquid had been conserved.
The capacity for conservation—the general
ability that lets the child see that a volume remains the same
despite a change in appearance—develops for lengths and numbers
at age 6 or 7 as well. For example, in the problem illustrated
below, the child will no longer say that there are more blue dots
in the top row on the right simply because they have been spread
Conservation of substance generally develops
a bit later, around age 7 or 8. Suppose, for example, that you
show a child three identical balls of clay, then leave the first
one intact, flatten the second one into a pancake, and divide the
third one up into smaller balls. If you then ask her whether the
second ball still contains “the same thing” (the same
amount) as the first, and she is less than 7 or 8 years old, she
will answer that it contains less, because it is flatter. But if
she is 7 or 8 or older, she will not be fooled by appearances.
Conservation of area is the last kind to
be mastered—often not until age 9 or 10. At that age, children
will know, for example, that even though the four yellow squares
shown below seem to occupy more area when they are grouped together
than when they are spread apart, in reality they do not.
Lastly, here is a problem that children who
are still at the concrete operations stage cannot solve, but that
adolescents (and adults) at the formal operations stage can, with
a little time and effort, to be sure. Say you have a deck of cards
that supposedly follows this rule: if there is a vowel on one side
of a card, then there has to be an even number on the other. Subjects
are told that each card has a letter on one side and a number on
the other. Which of the four cards shown here do you have to turn
over before you can tell whether they follow this rule? (The answer
appears below, but try to figure it out for yourself before you
The answer is: the E card and
the 7 card. For the rule to be true, the E card absolutely must
have an even number on the other side, so you must turn it over
to check. And since 7 is an odd number, you have to turn the 7
card over to make sure there is no vowel on the other side, because
that would break the rule. Since the rule does not say anything
about what should be on the other side of a card with a consonant,
such as K, and does not say that there has to be a vowel
on the other side of a card with an even number, such as 4, you
do not need to check those cards!
Contrary to what educators
had long believed before Piaget came along, children are
not just empty “containers” to be filled up with
knowledge. On the contrary, they truly act as “lone
scientists”, constantly creating and testing
their own theories about the world.
This is especially true of adolescents who have reached the
formal operations stage. For example, if you ask a teen to
find out what makes a pendulum swing faster or slower, he or
she will probably start by testing a long string with a light
weight at the end, then the same length of string with a heavier
weight, then a shorter string with the lighter weight, and
finally the shorter string with the heavier weight. From these
observations, which actually constitute a simple scientific
experiment, the teen will deduce that the shorter the string,
the faster the pendulum swings, and that the weight at the
end of the string makes no difference.
In experiments conducted
with pregnant women and their fetuses during the final weeks
of pregnancy, the mothers were asked first to keep silent
for three minutes and then to sing a song, while their babies
were filmed in the womb by means of ultrasound. When the
mothers began to sing, all the babies instantly began to
move, and their heartbeats accelerated. But when numerous
films were compared, it was found that the babies’ reactions
varied widely, ranging from very lively to quite subdued.
Since any given song inevitably has
a particular emotional overtone, it would seem that a baby’s
interactions with its mother’s emotions begin to shape
its temperament even while it is still in the womb.
Similarly, when a mother lets herself
form certain mental images, they too can have somatic manifestations
that affect the fetus. For example, it is known that some small
molecules generated by stress pass through the filter
of the placenta and
influence the fetus’s subsequent development.
Greenspan falls in the latter group. On the
basis of his experience in working with autistic children,
Greenspan believes that intelligence is structured by
affective (emotional) experience. Contrary to the traditional
concept of development, which separates emotion from
reason, Greenspan believes that emotions play a central
role in learning and in the development of our intellectual
faculties (for one example of how, follow the Experiment
Module link to the left).
Thus the essence of Greenspan’s vision of development
runs counter to Piaget’s and gives more weight than
even Freud did to the role of our early emotional experiences
in the development of our intellectual and social faculties.
So what does each child need in order to
develop successfully, according to Greenspan? First of all, a
safe, secure environment in which he or she can develop a relationship
with a stable, protective adult. The rich, continuous interactions
that begin with such an adult at the very start of life can them
become increasingly subtle and complex. Children can then experiment,
find solutions, take risks, fail, and try something else, all
within limits and structures clearly established by the adults
in their lives.
of intervention that Greenspan recommends for working with
children is called “floor time”: time spent
on the floor, following children in their play. The main
idea is to take whatever activity the child initiates as
the point of departure, then try to introduce an affective
interaction into this activity.
For example, if a father and his daughter start taking
turns lining up blocks in a row on the floor, the child
will understand the routine and wait for her father to
put his block down before she puts hers. If the father
then puts down two blocks in a row, or puts his block down
out of line, his daughter will want to correct the error.
The father has thus created an opportunity to, in Greenspan’s
terms, “open and close a circle of communication”.
In such situations, far from posing an
obstacle to clear, logical thinking, emotions constitute the “glue” that
binds all aspects of intellectual and social development together.
In fact, abstract concepts are often classifications based on
emotional experiences in the real world.
Consider the mathematical concept of quantity, for example, which
children derive from two kinds of emotional experiences. The
first is the feeling of “a lot ”that children learn
when they receive more things than they were expecting. The second
is the feeling of “a few ” that they get when they
receive fewer things than they would like. Children thus assimilate
the concept of quantity on the basis of expectations with a strong
affective component. Later, children can systematize these experiences
with numbers, so that 10 becomes “a lot ” and 2 becomes “a
few”. Thus children’s understanding of supposedly
cold, logical mathematics is actually anchored in the affective
experiences through which they first learned concepts of numbers.
According to Greenspan, this same principle extends to more abstract
concepts such as justice. Tomorrow’s judges will have to
study the laws by which society codifies this concept, but their
intimate knowledge of what justice means will come from their
personal lives and their own experiences of having been treated
fairly or unfairly.
In Greenspan’s model, it is
therefore essential for each child to develop the feeling of
his or her individuality. It is through this feeling of being
themselves and not someone else that children become capable
of desiring and of having intentions. Every effort should therefore
be made to encourage whatever helps children build this feeling
of having their own personalities.
Erikson’s contribution to developmental
psychology also emphasizes the sound development of the
feeling of personal identity. Unlike Freud, who believes
that most of our personality structure has been determined
by age 5, or Piaget, who believes that the kind of reasoning
that we master in adolescence (formal operations) is
fairly close to the kind that we use for the rest of
our lives, Erikson says that our personalities continue
to develop throughout our lives. He distinguishes eight
stages of psychological development, in each of which
a particular psychological crisis predominates, triggered
by a predominant type of interaction with the social
The quality of resilience has
been observed in some children who were abused or traumatized
by various atrocities
committed in the course of history. These resilient children
developed normally afterward and in some cases even seemed
better equipped to face adversity than most people are. One
theory is that traumatized children who show resilience acquired
a “primitive confidence” between birth and 12
months of age that subsequently let them maintain the hope
of meeting someone who would help them to resume their development.
Resilience is a complex phenomenon in which developmental biological
forces join with the social context to create a representation
of the self that lets the individual forge a meaningful personal
Because the brain’s
various systems do not all become mature at the same time,
the critical periods for various brain functions differ.
The critical period for each of these functions represents
a vulnerable interval when the individual is highly sensitive
to influences from the environment, including traumatic
experiences. Traumas suffered in childhood can therefore
permanently affect the way a person’s mind is organized.
IN COGNITIVE DEVELOPMENT
During the first years of life, the influence
of the environment on development is crucial. The most pronounced
changes induced by the environment occur during windows of time
called critical periods.
All critical periods have certain basic properties in common.
First, they all involve a time window during which a given behaviour
is more sensitive to specific environmental influences. These
influences are even necessary for the normal development of the
behaviour in question. Once the critical period is over, the
behaviour is no longer significantly affected by the presence
or absence of these environmental stimuli. And, as a corollary,
if the individual is not exposed to the appropriate stimuli during
the critical period, it is difficult if not impossible to compensate
for this lack later on.
For instance, people who are deprived of
the use of one of their senses during a certain critical period
at the start of their lives may still have permanent gaps in
this sense even if they reacquire the use of it later on. There
have been cases where people who were born blinded by cataracts
had them removed and their sight restored between ages 10 and
20. Subsequently, they were able to perceive
colours, but would always have great difficulty in distinguishing
Also, if children are emotionally deprived or mistreated
during certain periods of their development, it can have
an irreversible impact on their
emotional equilibrium when they become adults. Many
authorities regard the first three years of life as a critical
period for the neural pathways involved in forming social
and emotional relationships. If children are exposed to
repeated negative experiences during this period, their
social and emotional equilibrium may remain fragile for
the rest of their lives, and they may be subject to episodes
of anxiety or depression.
Many studies have shown that such mood
disorders are accompanied by hyperactivity
of the hypothalamic-pituitary-adrenal (HPA) axis. This axis
is directly involved in controlling stress: the levels of cortisol
in the blood, like those of CRH in the cerebrospinal fluid, are
very high in severely depressed patients.
Experiments have shown that in rats, sensory experience early
in development regulates expression of the genes that encode
the receptors for glucocorticoids. Young rats that receive attentive
maternal care develop more receptors of this type in their hippocampus
and fewer receptors for CRH in their hypothalamus. As a result,
when these rats become adults, they tend to display relatively
The explanation is that when cortisol
activates the receptors for glucocorticoids in the hippocampus,
there is a negative feedback effect on the activity of the
HPA axis. In people who have experienced affective deficits
during the critical first three years of their lives, this
control loop is disrupted, which explains the hyperfunctioning
of this neural/endocrinal axis and the associated chronic stress.