SCIENCE
Special PSYCHOLOGICAL Section
PIAGET:
A Centennial Celebration
C.J. Brainerd
University of Arizona
Piaget, Freud, Skinner, An odd thing about the three leading
names of 20th-century psychology is thai, despite the deep differences that divide their work, each had much to say about
child development. The entire rationale for psychoanalysis, of
course, was a theory of development, Freud's psychosexual
stages. We need only remind ourselves of air cribs, token econFirst, it led him to forgo play and other normal childhood
omies, teaching machines, programmed instruction manuals, pursuits and turn to serious scientific research while still in
and today's computerized courseware to see what fertile elementary school. Like so many other people, he found surground child development supplied for Skinner's views.
cease from emotional turmoil in intellectual creation. Second,
It is Piaget, though, who was the quintessential developmen- his mother's difficulties fomented an intense interest in the
talist. The purpose of this special section of Psychological Sci- study of psychology. At first, naturally enough, he concenence is to honor his landmark contributions on the 100th anni- trated on abnormal personality, especially psychoanalysis. The
versary of his birth. In the articles that follow, eminent scholars result was surprising, however. He decided that he strongly
analyze Piaget's accomplishments and reflect upon their lasting preferred the study of cold cognition to that of abnormal perplace in the history of our discipline. In this historical introduc- sonality, a preference that was to last the rest of his life and for
tion, I sketch Piaget's biography, one that is little known in which he was much criticized.
comparison to those of Freud and Skinner.' I also describe
The scientific work that Piaget tackled as an elementary
some achievements that Piaget himself regarded as among his school student was in malacology rather than psychology. He
most important ones and comment upon one feature of his work was astonishingly precocious. At age 7, he wrote to the director
that has been of enduring significance to me.
of the Neuchatel natural history museum, Paul Godet, asking if
he might study the museum's moUusk collection after hours.
Godet not only agreed but undertook to tutor Piaget in techPIAGET'S LIFE
niques for collecting and classifying new specimens, Piaget published his first scientific article, a one-page report in Rameau de
Piaget was born in Neuchatel, Switzerland, in August of Sapin, in 1907 at age 10, By the time of Godet's death, in 1911,
1896 and died in Geneva in October of 1980, Along the way, he Piaget had written a series of reports on moUusks. On the basis
became, by a wide margin, the world's preeminent student of of those articles, he was offered, at age 14, the curatorship of
development. During the 1960s and 1970s, his theory of cogni- the Geneva museum of natural history. When, as a consetive development dominated the landscape the way Freud's ac- quence of this invitation, his age became widely known, some
count of psychosexual development had a generation before. journal editors would no longer publish his articles,
The phenomena that he discovered (e,g,, conservation conPiaget obtained his bachelor's degree in 1915, at age 18, and
cepts, object permanence) and his theoretical concepts (e.g,, his Ph,D, (with a dissertation on moUusks) 3 years later at the
stages, structures) remain standard fare in introductory psy- University of Neuchatel, He might have finished his Ph.D.
chology courses,
sooner had he been able to devote full time to graduate study.
Piaget's childhood was far from happy. His father was a In !915, however, he suffered a nervous breakdown and withmedieval-literature scholar who also wrote extensively on Neu- drew to the mountains for more than a year to recover. Thirtychatel history, Piaget admired his father greatly and adopted his five years later, he attributed this breakdown to the baleful
skeptical, scientific attitude at an early age. His mother, how- influence of philosophy. As an undergraduate, Piaget had, unever, suffered from what Piaget was later to characterize as "a der his godfather's direction, conducted an extensive program
rather neurotic temperament" and "poor mental health" cou- of reading in philosophy and had written many essays based on
pled with religious enthusiasm (Evans, 1973, p. 106), This sit- his reading. He was later to describe this contact with philosouation had two lasting effects on Piaget,
phy, particularly with the creative evolution of Henri Bergson,
as an unfortunate encounter. Throughout his career, he was to
remain a persistent critic of philosophical speculation unchecked by the discipline of data, ultimately setting forth his
Address correspondence to CJ, Brainerd, Department of Educa- position in Insights and Illusions of Philosophy (1968). Some
tional Psychology, University of Arizona, Tucson, AZ 85721; e-mail: years ago, I heard George Mandler aptly summarize Pi^et's
brainerd@ccit,arizona,edu,
position as, "New Ph.D.'s in philosophy should not be permit1, Excellent biographical sources include Evans (1973), an autobio- ted to publish until they have completed postdoctoral training in
graphical chapter (Piaget, 1952), and several interviews that Piaget gave
experimental psychology,"
late in life (e.g,, Piaget & Inhelder, 1970), Elkind's article in this issue
Before finishing his dissertation, Piaget decided that psychoprovides further biographical information about Piaget's adolescence.
VOL, 7, NO, 4, JULV 1996
Copyright 19% American Psychological Society
191
PSYCHOLOGICAL SCIENCE
Piaget
Books Featured in This Special Section
Piaget, J, (1918), Reserche. Lausanne, Switzerland: Concorde,
Picket, J, (1926), The language and thought of the child. New York:
Harcourt, Brace, (Trans, by M, Gabain; original French publication: 1923)
Piaget, J. (1928), Judgment and reasoning in the child. New York:
Harcourt, Brace. (Trans, by M, Warden; original French publication: 1924)
Piaget, J, (1929). The child's conception of the world. New York:
Harcourt, Brace. (Trans, by i. Tomlinson and A, Tomlinson;
original French publication: 1926)
Piaget, J. (1930), The child's conception of physical causality. London: Kegan Paul. (Trans, by M, Gabain; original French publication: 1927)
Piaget, J. (1932), The moral judgment of the child. London: Kegan
Paul. (Trans, by M. Gabain; original French publication: 1932)
Piaget, J, (!952), The origins of intelligence in children. New York:
International Universities Press, frrans, by M, Cook; original
French pubiicalion: 1936)
Piaget, J, (1954), The construction of reality in the child. New York:
Basic Books, (Trans, by M, Cook; original French publication:
1937)
Piaget, i. (1952), The child's conception of number, London: Routledge & Kegan Paul, (Trans, by C, Gattegno and F,M, Hodgson;
original French publication: !941)
Piaget, J, (1942), Classes, relations et nombres. Paris: Vrin,
Piaget, J. (1951), Play, dreams, and imitation in childhood. New
York: Norton, (Trans, by C, Gattegno and F,M, Hodgson; original French publication: 1945)
Piaget, J, (1%9), The child's concept of time. New York: Ballantine,
(Trans, by A,J, Pomerans; original French publication: 1946)
Piaget, J, (1950), The psychology of intelligence. London; Routledge
& Kegan Paul. (Trans, by M, Piercy and D,E, Berlyne; original
French publication: 1947)
Piaget, J,, & Inhelder, B, (1956), The child's conception of space.
London: Routledge & Kegan Paul. (Trans, by F,J, Langdon and
J,L, Lunzer; original French publication; !948)
Piaget, J, (1949), Traite de logique. Paris; Colin.
Piaget, J, (1950), Logic and psychology, Manchester, England:
Manchester University Press, (Trans, by W. Mays and F, Whitehead)
Piaget, J, (1952). Essai sur les transformations des operations
logiques. Paris; Presses Universitaires de France,
Inhelder, B,, & Piaget, J, (1958), The growth of logical thinking from
childhood to adolescence. New York: Basic Books, (Trans, by
A, Parsons and S, Milgram; original French publication; 1955)
Piaget, I, (1969). Mechanisms of perception. New York; Basic
Books, (Trans, by G,N, Seagrim; original French publication:
1%1))
Piaget, J,, & Inhelder, B, (1971), Mental imagery in the child. New
York: Basic Books, (Trans, by P.A, Chilton; original French
publication; 1966)
Piaget, J, (1971), Biology and knowledge. Chicago: University of
Chicago ftess. (Trans, by B, Walsh; original French publication;
1%7))
Piaget, J. (1968), Insights and illusions of philosophy. New York:
World. (Trans, by W, Mays; original French publication; 1968)
Piaget, J,, & Inhelder, B, (1973), Memory and intelligence. New
York; Basic Books, (Trans, by A,J, Pomerans; original French
publication; 1968)
Piaget, J, (1968), On the development of memory and identity.
Worcester, MA: Ciark University Press, (Trans, by E, Duckworth)
Piaget, ,J, (1970), Genetic epistemology. New York: Columbia University Press, (Trans, by E, Duckworth)
Piaget, J. (1970). Science of education and psychology of the child.
New York: Oxford University Press, (Trans, by D. Coltman;
original French publication; 1970)
Piaget, J. (1978). Behavior and evolution. New York: Random
House. (Trans, by D. Nicholson-Smith; original French publication: 1978)
Raget, J, (1980). Language and learning. Cambridge, MA; Harvard
University Press. (Trans, by M. Piatelli-Mmarini)
Piaget, J. (1981). Intelligence and affectivity. Palo Alto, CA; Annual
Reviews. (Trans, by T.A, Brown, C,E. Kaegi, and M,R, Rosenzweig)
192
logical research was where his real interests lay. While still an
undergraduate, he had committed himself to developing a biological theory of knowledge, which eventually came to be called
genetic epistemology. He had also concluded, through his studies of mathematical logic and philosophy of science, that logic is
inherent in action and that the roots of logic are therefore to be
found in the organization of action. It was this conclusion that
formed the basis for Piaget's hypothesis that even the most
sophisticated forms of human reasoning are motor activities
carried out on a symbolic plane,
Piaget lacked the training in psychological methodology that
was necessary to pursue his interests. He remedied this deficiency via postdoctoral work, first at the University of Zurich
(1918-1919) and then in Paris at the Sorbonne (1919-1921), A
watershed event occurred when he secured a research assistantship in Alfred Binet and Theodore Simon's laboratory in a
Paris elementary school. Binet was dead by this time, but Simon assigned Piaget the job of standardizing the French translation of a reasoning test that Cyril Burt had recently developed.
Piaget had his own ideas. Although he dutifully recorded the
correct and incorrect answers that were necessary to standardize Burl's test, he also asked children to explain their answers,
exploring those explanations with psychiatric interviewing
techniques that he had learned at the Sorbonne, For Piaget,
those explanations opened up vistas of the fundamentally different ways in which children and adults conceptualize the
world around them. Crucially, he found that children's explanations of incorrect answers were far more illuminating than
their explanations of correct answers. This procedure of requesting explanations, particularly of incorrect answers, and
probing children with psychiatric-style interviewing soon
evolved into Piaget's famed clinical method,
Piaget's first three psychological articles, based on this
work, appeared in 1921, They prompted Edouard Claparede to
offer him the directorship of research at the Rousseau Institute
in Geneva. Piaget arrived there in the same year with a wellformed plan to spend 2 or 3 years studying children's reasoning,
a plan that then took a half-century to complete. The initial
results appeared in his first five scientific books. The Language
and Thought of the Child (1923), Judgment and Reasoning in
the Child (1924), The Child's Conception of the World (1926),
The Child's Conception of Physical Causality (1927), and The
Moral Judgment of the Child (1932). Later in life, Piaget stated
that these books were premature, that their conclusions were
founded on insufficient data, and that he would not have published them had he known that they would be widely read. They
were widely read, however, and The Language and Thought of
the Child, in particular, earned him an international reputation
before he was 30,
In 1925, Piaget assumed the chair of philosophy at the University of Neuchatel, while retaining his position at the Rousseau Institute. His first child was born in that same year, with
two others following in 1927 and 1931. During this time, Piaget
and his wife studied nonverbal expressions of intelligence in
their infants (see Fischer and Hencke's article). Their findings
were to appear in Piaget's influential books on infant cognition.
The Origins of Intelligence in Children (1936), The Construction
VOL, 7, NO. 4, JULY 19%
PSYCHOLOGICAL SCIENCE
C.J. Brainerd
of Reality in the Child (1937), and Play, Dreams, and Imitation
in Childhood (1945). An important outcome of those infant studies was that Piaget modified the clinical method that he had
used in his first five books. Whereas the method had been a
purely verbal question-and-answer procedure, Piaget concluded that because the expression of intelligence was, at bottom, nonverbal, the method must henceforth feature the manipulation of concrete objects.
The decade from 1929 to 1939 was an unusually productive
one, even by Piaget's standards. In 1929, he returned to fulltime duties in Geneva as professor of the history of scientific
thought and co-director of the Rousseau Institute. There he
encountered two exceptionally able students. Barbel Inhelder
and Alina Szeminska. With their collaboration, Piaget conducted the research for which he subsequently became best
known. That research dealt with the emergence of elementary
concepts of biology, mathematics, and physics in children's
thinking, and it introduced the familiar conservation concepts.
This same work led to his stage hypothesisthe conjecture that
cognitive development passes through a sequence of qualitatively distinct periods, an intellectual analogue of morphogenesis. This idea reached full flower after World War II with the
articulation of his grand theory of stage and structure.
From the outbreak of the war through the early 1950s, Piaget's research revolved around two major themes, one theoretical and the other empirical. On the theoretical side, he completed work on a formal, mathematical account of cognitive
structure that he had begun two decades earlier. Piaget's experiments with children, together with his studies of mathematics and logic, had convinced him that certain branches of mathematics (group theory and lattice theory) and logic (propositional logic) could provide a calculus for reasoning during the
last two stages of cognitive development (the concrete- and
formal-operational periods). He described his proposed calculus in a book that dealt with the concrete-operational period.
Classes, relations et nombres (1942); a book that dealt with
both the concrete- and the formal-operational periods. Traite de
logique (1949); and a book that dealt with the formaloperational period, Essai sur les transformations des operations logiques (1952). These volumes are among the most difficult in all of Piaget's vast bibliography, and only the second has
ever been translated into English (in edited form).
On the empirical side, Piaget's work during this period led to
the subsequent publication, with Inhelder, of a long series of
books dealing with the development of mathematical and
scientific reasoning. The list of topics included children's and
adolescents' understanding of classification, geometry, movement, rules of scientific inference, propositional logic, probability, space, speed, and time.
By the early 1950s, Piaget's grand theory of stage and structure in cognitive development been had formulated. He had first
unveiled it in a series of lectures at the College de France during
World War II. Later, with Inhelder, he presented the theory in
more elaborate form at a series of United Nations Educational,
Scientific and Cultural Organization (UNESCO) conferences
that were held during the late 1940s and early 1950s. During that
period, Piaget was heavily involved in UNESCO's efforts to
improve the lot of children in the postwar era. From 1945 to
VOL. 7, NO. 4, JULY 19%
1950, he served as president of the Swiss Commission of
UNESCO and headed the Swiss delegations to international
conferences of UNESCO. Although the lure of uncompleted
research caused him to reduce his UNESCO commitments in
1950, he continued as a member of its executive committee for
some years thereafter.
The remainder of Piaget's career, from the late 1950s until
his death, is what I like to think of as his psychological period,
by which I mean that it was a time when he returned to themes
that all psychologists would regard as part of the core of our
science. Hitherto, Piaget had labored in splendid isolation,
though his work was internationally recognized (see Kessen's
article). He had concentrated on topics that were, to say the
least, outside the mainstream. The mere fact that he studied
complex cognition during the heyday of behaviorism was heretical enough, Gestalt psychologists being the only other contemporary group to devote much effort in that direction. In
addition, the varieties of cognition that he studied
conservation laws, principles of chance and probability, concepts of projective geometrywere rarified and most assuredly
not the stuff of American intelligence tests.
The model of stage and structure that Piaget had devised by
the early 1950s was a global theory in the tradition of early
schools of psychology. Surely a theory of such scope must have
deep implications for mainstream psychological topics such as
emotion, learning, memory, and perception. Many of the books
that appeared during the last two decades of Piaget's life were
directed toward spelling out those implications. This is obvious
enough from the tities of some of the more notable volumes:
Intelligence and Affectivity (1981), Language and Learning
(1980), Mechanisms of Perception (1%1), On the Development
of Memory and Identity (1968), Memory and Intelligence (1968,
with Inhelder), and Mental Imagery in the Child (1966, with
Inhelder). A recurrent theme of these later volumes was that
children's abilities in some target domain (e.g., mental imagery,
memory) are constrained in specific ways by the stages and
structures of Piaget's theory. These books introduced a plethora of intriguing new empirical phenomena, a case in point being the long-term memory improvement effect (the finding that
children's recall of certain types of material is better 6 months
or a year after exposure than a few days after exposure).
When scholars look back on Piaget's life, there is much variability in what they find most remarkable. For my part, I have
always been struck by two things, though perhaps they say
more about me than about Piaget. The fu-st is the almost overpowering coherence of his work. By 1915, Piaget had identified
the problem that was to occupy him throughout his career, the
articulation of a biological theory of knowledge. This work was
not completed until Biology and Knowledge was published in
1967. Although the solution required five decades to work out,
Piaget had arrived at the principle on which the solution was to
rest while stiU an adolescentnamely, structuralism, the notion
that there are cognitive totalities (later to be called structuresof-the-whole) that are qualitatively distinct from their parts atid
that impose an inescapable organization on intelligence. By his
mid-50s, Pis^et had forgotten that he had foreseen the core
themes of his research as an adolescent. Then, in the course of
reexamining some of his undergraduate writings, he was
193
PSYCHOLOGICAL SCIENCE
Piaget
Piaget's response was to acknowledge that construction is
constrained by the physical laws of the environment and the
biological possibilities of the child. (Although vehicle inventors
may build a great variety of transportation machines, their inventions cannot violate the laws of thermodynamics nor exceed
the speed of light.) To most people, however, the restrictions
imposed by physics and biology seem far too broad and nonspecific to produce such universal outcomes. This problem has
undoubtedly contributed to the popularity of nativistic accounts
of development since Piaget's death (see Gopnik's article).
Piaget recognized the problem and admitted, late in life, that
"this idea of construction of novelty, this is the idea that is most
difficult to make understood" (Evans, 1973, p. 39).
The second contribution that Piaget regarded as truly fundamental, stracturaiism, is the notion that there are cognitive totalities and that they are the essence of human intelligence. At
a more specific level, Piaget thought that the relationship between biology and intelligence, the problem that he had set for
himself as an adolescent, was a question of knowledge structures and that certain mathematical formalisms could capture
WHAT PIAGET THOUGHT WAS IMPORTANT
those structures. He thought, further, that these structures proABOUT PIAGET
duce stable states of equilibrium that correspond to his major
periods of cognitive growth. It is structures, then, not concepts
During the last decade of his life, Piaget was often asked to such as conservation or object permanence, that are the real
identify his most important achievements. There were two that outcomes of knowledge construction. This view led Piaget to
he invariably mentioned: constructivism and structuralism (see describe cognitive development not in terms of specific intelFlavell's and Siegler and Ellis's articles for additional discus- lectual skills that children acquire at different ages but in terms
sion of these topics). Although both were central to Piaget's of the knowledge structures that are supposedly responsible for
theory, there are some difficulties inherent in each that has the expression of those skills.
made them sources of continuing controversy.
This all-is-structure hypothesis has remained controversial
Pis^et's version of constructivisnn should not be confused because, like constructivism, it raises some questions that Piawith Bartlett's (1932) better known theory of the same name. get did not answer to most people's satisfaction. Two important
Piagetian constructivism is the doctrine that during ontogene- ones are concerned with the ethereal nature of these structures
sis, our knowledge of the world emerges via a process of cre- and with the fact that they represent task relationships rather
ative invention (not, as in Bartlett's case, by merely failing to than relationships between psychological processes. Regarding
encode information that does not fit with current schemata). the former question, the knowledge structures that Piaget proAccording to this doctrine, knowledge is the product neither of posed in the aforementioned logic books of 1942, 1949, and 1952
discovering preformed ideas, in the rationalist sense, nor of (e.g., groups and lattices) were borrowed chiefly from abstract
learning, in the empiricist sense (see Fischer and Hencke's and algebra. As psychological constructs go, they are, therefore,
Siegler and Ellis's articles for examples of knowledge construc- very abstract indeed. Although it might be possible to conceive
tion during infancy and childhood). Rather, knowledge is liter- of how a specific reasoning ability, such as a conservation conally created by infants and children from whole cloth as expe- cept, could be acquired via a construction process, it is hard to
rience interacts with their biological predispositions. This same imagine how the dihedral group D2, an algebraic structure that
idea supplied Piaget's solution to the nature-nurture debate: Piaget proposed in connection with several forms of scientific
Knowledge is a by-product of interactions between heredity reasoning, could be acquired via this same route.
and environment, and construction is the medium of those inThe second question about all-is-structure is even more elteractions.
ementary. Piagel's knowledge structures were formalizations of
The question that constructivism has long posed for students the structure of the tasks that he used, not formalizations of the
of development is, how can cognitive development be a process structure of psychological processes (Brainerd, 1978). That is,
of creative invention when the types of knowledge that make up they were representations of relationships between variables in
the core expressions of intelligence are so universal? With nor- certain reasoning problems (e.g., the physical operations carmal infants Mid children, Piaget's familiar stage-related con- ried out in tasks such as pendulum, problems, fulcrum problems,
cepts (object permanence, conservation, spatial perspective probability problems, and proportionality problems). It is a
taking, and the like) exhibit no variability with respect to either huge inductive leap to assume, from the fact that children or
their end states or the sts^es through which they pass. How can adolescents solve these problems, that there are isomorphisms
such uniformity be reconciled with the notion that, for each (or even homomorphisms) between such task structures and the
child, these concepts are novel inventions? Would it not be cognitive structures that are brought to bear to effect solutions.
more logical to expect that individual differences would be the Much research published during the 1970s and 1980s demonrule?
strated the hazards of such leaps.
shocked to discover that these writings anticipated his subsequent work "in a striking manner" (Evans, 1973, p. 105). Obviously, Piaget was something of a packrat.
The other thing that I find most striking is Piaget's sheer
productivity. Adjectives such as enormous, staggering, and stuptendous come to mind. Such terms do not seem even mildly
hyperbolic when one reflects upon the raw numbers. For instance, the CM-d catalogue of my university's library lists 110
books that were either written or edited by Piaget. There are
some duplications, naturally, and some English translations of
original French volumes. When those are stripped away, 73
books remain, all of them weighty. In other words, Piaget averaged about one and one quarter books per year between the
publication of his first volume and his death. And this count
leaves out his journal articles and contributions to other authors' volumes, which are far more extensive than his books.
194
VOL. 7, NO. 4, JULY 1996
PSYCHOLOGICAL SCIENCE
C,J. Brainerd
peting explanations that Piaget explored: The numerical disparity between the subordinate sets may create visual illusions;
Students of development often query one another as to Pia- children may not understand that every object without excepget's most profound accomplishments. Indeed, the contributors tion belongs to the superordinate set; children may misinterpret
to this special section were confronted with this question. Their the type of numerical comparison that is being requested; chilanswers follow.
dren may be unable to think simultaneously about parts and
When this question has been asked of me, one answer, wholes. The task suggests stiU ftuther explanations that have
which grows out of many journeys along trails that Piaget been subjects of numerous experiments by other investigators.
blazed, has always seemed obvious. That answer is that it is Such work continues apace.
those paradigms, those wonderful, wonderful paradigms. PiaThat, for me at least, Piaget's paradigms and associated findget's work is without parallel as a soiu-ce of ingenious experi- ings are his most enduring contributions in no way diminishes
mental techniques for unlocking the mysteries of children's his achievements as a theorist. On the contrary, the same can
thinking. When I say this, I am making a purely normative be said of most of the other great figures of the first century of
statement for which the evidence is abundant. It is a brute fact psychological science. In classical learning theory, for instance,
that Piagetian measures such as class inclusion, conservation, what remains of continuing significance in the writings of Pavdeferred imitation, egocentric and socialized speech, horizon- lov, Hull, Skinner, and Estes is not their theoretical principles,
tality, perspective taking, object permanence, subjective and important as those principles were in the evolution of learning
objective moral judgment, and transitive inference, to name theory. Rather, as we all know, it is the respondent conditioning
only a few, have each produced thousands of studies by inves- paradigm and effects such as stimulus generalization, the distigators around the world. The bulk of what we know about crimination learning paradigm and effects such as transposition,
cognitive development consists of data generated by such par- the operant conditioning paradigm and effects such as partial
adigms.
reinforcement, and the probability learning paradigm and efThe dominance of Piagetian measures can be traced to the fects such as probability matching to which interest still atfact that they produce data that are at once counterintuitive taches.
(children reason in wildly illogical ways about problems whose
This circumstance is a consequence of our youth. We are too
solutions are self-evident to adults) and richly evocative of hy- young a science to hope that our theoretical concepts, concepts
potheses about the nature of children's thinking. To take but that in Piaget's case were mostly borrowed from early evoluone example, consider chapter 7 in what is probably Piaget's tionary biology and epistemology, can survive the test of even
best known book. The Child's Conception of Number (1941). a few decades. We can hope, however, that our paradigms and
There, he introduced one of his most extensively studied par- findings will survivethat 500 years from now, all-or-none
adigms, class inclusion. (He had introduced his most famous learning, the serial position curve, the magical number 7, and,
one, number conservation, a few chapters earlier!) Class- yes, children's illogical solutions of conservation problems will
inclusion tasks are very simple problems whose solutions are so still be regarded as having taught important lessons about huineluctable that, seemingly, no one could fail to see them. The man cognition.
child is presented with an array consisting of everyday objects
that can be divided into two or more numerically unbalanced
sets (e.g., seven toy cows, five toy horses, and three toy dogs).
REFERENCES
All of these objects belong to a single superordinate set (e.g.,
animals). The child is questioned about the relationship be- Bartlett, F.C. (1932). Remembering: A study in experimental and social psychology. Cambridge, England: Cambridge University Press.
tween the superordinate set and the largest subset (Are there
cognitive-developmental theory. The
more cows or more animals?). The answer is obvious because a Brainerd, C.I. (1978). The stage question in73-213.
Behavioral and Brain Sciences, 1, 1
superordinate set must have more members than any set that is Evans, R.L. (1973). Jean Piaget: The man and his ideas. New York: Dutton.
included in it. Nevertheless, children claim the opposite, that Piaget, J. (1952). Autobiography. In E.G. Boring, H. Werner, H.S. Langfeld, &
R.M. Yerkes (Eds.), A history ofpsycholop in autobiography (Vol. IV, pp.
the largest subordinate set has more members than the super237-256). Worcester. MA: Clark University Press.
ordinate set, and they continue to do so until the surprisingly Piaget, J., & Inhelder, B. (1970). A conversation with Jean Piaget and Barbel
advanced age of 9 or 10. The task itself suggests several comInhelder. Psychology Today, i(12), 25-32.
VOL. 7, NO. 4, JULY 1996
195