THE COURSE OF COGNITIVE GROWTH

JEROME S. BRUNER1

Harvard University

I SHALL take the view in what follows that thedevelopment of human intellectual functioningfrom infancy to such perfection as it may

reach is shaped by a series of technological ad-vances in the use of mind. Growth depends uponthe mastery of techniques and cannot be under-stood without reference to such mastery. Thesetechniques are not, in the main, inventions of theindividuals who are "growing up"; they are, rather,skills transmitted with varying efficiency and suc-cess by the culture—language being a prime ex-ample. Cognitive growth, then, is in a major wayfrom the outside in as well as from the inside out.

Two matters will concern us. The first has todo with the techniques or technologies that aidgrowing human beings to represent in a manage-able way the recurrent features of the complex en-vironments in which they live. It is fruitful, Ithink, to distinguish three systems of processing in-formation by which human beings construct modelsof their world: through action, through imagery,and through language. A second concern is withintegration, the means whereby acts are organizedinto higher-order ensembles, making possible theuse of larger and larger units of information for thesolution of particular problems.

Let me first elucidate these two theoretical mat-ters, and then turn to an examination of the re-search upon which they are based, much of it fromthe Center for Cognitive Studies at Harvard.

On the occasion of the One Hundredth Anni-versary of the publication of Darwin's The Originof Species, Washburn and Howell (1960) pre-sented a paper at the Chicago Centennial celebra-tion containing the following passage:

It would now appear . . . that the large size of the brainof certain hominids was a relatively late development andthat the brain evolved due to new selection pressures afterbipedalism and consequent upon the use of tools. Thetool-using, ground-living, hunting way of life created thelarge human brain rather than a large brained man dis-

1 The assistance of R. R. Olver and Mrs. Blythe Clinchyin the preparation of this paper is gratefully acknowledged.

covering certain new ways of life. [We] believe this con-clusion is the most important result of the recent fossilhominid discoveries and is one which carries far-reachingimplications for the interpretation of human behavior andits origins. . . . The important point is that size of brain,insofar as it can be measured by cranial capacity, has in-creased some threefold subsequent to the use and manu-facture of implements. . . . The uniqueness of modern manis seen as the result of a technical-social life which tripledthe size of the brain, reduced the face, and modified manyother structures of the body [p. 49 f.].

This implies that the principal change in manover a long period of years—perhaps 500,000 thou-sand—has been alloplastic rather than autoplastic.That is to say, he has changed by linking himselfwith new, external implementation systems ratherthan by any conspicuous change in morphology—"evolution-by-prosthesis," as Weston La Barre(1954) puts it. The implement systems seem tohave been of three general kinds—amplifiers of hu-man motor capacities ranging from the cutting toolthrough the lever and wheel to the wide variety ofmodern devices; amplifiers of sensory capacitiesthat include primitive devices such as smoke signal-ing and modern ones such as magnification andradar sensing, but also likely to include such "soft-ware" as those conventionalized perceptual short-cuts that can be applied to the redundant sen-sory environment; and finally amplifiers of humanratiocinative capacities of infinite variety rangingfrom language systems to myth and theory andexplanation. All of these forms of amplificationare in major or minor degree conventionalized andtransmitted by the culture, the last of them prob-ably the most since ratiocinative amplifiers involvesymbol systems governed by rules that must, foreffective use, be shared.

Any implement system, to be effective, must pro-duce an appropriate internal counterpart, an ap-propriate skill necessary for organizing sensori-motor acts, for organizing percepts, and for organiz-ing our thoughts in a way that matches them tothe requirements of implement systems. These in-ternal skills, represented genetically as capacities,are slowly selected in evolution. In the deepest

1

AMERICAN PSYCHOLOGIST

sense, then, man can be described as a species thathas become specialized by the use of technologicalimplements. His selection and survival have de-pended upon a morphology and set of capacitiesthat could be linked with the alloplastic devicesthat have made his later evolution possible. Wemove, perceive, and think in a fashion that de-pends upon techniques rather than upon wired-inarrangements in our nervous system.

Where representation of the environment is con-cerned, it too depends upon techniques that arelearned—and these are precisely the techniquesthat serve to amplify our motor acts, our percep-tions, and our ratiocinative activities. We knowand respond to recurrent regularities in our en-vironment by skilled and patterned acts, by con-ventionalized spatioqualitative imagery and selec-tive perceptual organization, and through linguisticencoding which, as so many writers have remarked,places a selective lattice between us and the physi-cal environment. In short, the capacities that havebeen shaped by our evolution as tool users are theones that we rely upon in the primary task of rep-resentation—the nature of which we shall considerin more detail directly.

As for integration, it is a truism that there arevery few single or simple adult acts that cannot beperformed by a young child. In short, any morehighly skilled activity can be decomposed into sim-pler components, each of which can be carried outby a less skilled operator. What higher skills re-quire is that the component operations be com-bined. Maturation consists of an orchestration ofthese components into an integrated sequence. The"distractability," so-called, of much early behaviormay reflect each act's lack of imbeddedness inwhat Miller, Galanter, and Pribram (1960), speakof as "plans." These integrated plans, in turn, re-flect the routines and subroutines that one learnsin the course of mastering the patterned nature ofa social environment. So that integration, too, de-pends upon patterns that come from the outside in—an internalization of what Roger Barker (1963)has called environmental "behavior settings."

If we are to benefit from contact with recurrentregularities in the environment, we must representthem in some manner. To dismiss this problem as"mere memory" is to misunderstand it. For themost important thing about memory is not storageof past experience, but rather the retrieval of whatis relevant in some usable form. This depends

upon how past experience is coded and processedso that it may indeed be relevant and usable in thepresent when needed. The end product of such asystem of coding and processing is what we mayspeak of as a representation.

I shall call the three modes of representationmentioned earlier enactive representation, iconicrepresentation, and symbolic representation. Theirappearance in the life of the child is in that order,each depending upon the previous one for its de-velopment, yet all of them remaining more or lessintact throughout life—barring such early acci-dents as blindness or deafness or cortical injury.By enactive representation I mean a mode of rep-resenting past events through appropriate motorresponse. We cannot, for example, give an ade-quate description of familiar sidewalks or floorsover which we habitually walk, nor do we havemuch of an image of what they are like, Yet weget about them without tripping or even lookingmuch. Such segments of our environment—bicycleriding, tying knots, aspects of driving—get repre-sented in our muscles, so to speak. Iconic repre-sentation summarizes events by the selective or-ganization of percepts and of images, by the spatial,temporal, and qualitative structures of the percep-tual field and their transformed images. Images"stand for" perceptual events in the close but con-ventionally selective way that a picture stands forthe object pictured. Finally, a symbol system rep-resents things by design features that include re-moteness and arbitrariness. A word neither pointsdirectly to its referent here and now, nor does itresemble it as a picture. The lexeme "Philadelphia"looks no more like the city so designated than doesa nonsense syllable. The other property of lan-guage that is crucial is its productiveness in com-bination, far beyond what can be done with imagesor acts. "Philadelphia is a lavendar sachet inGrandmother's linen closet," or (x + 2)2 = x2 + 4x+ 4 = X(X + 4) + 4.

An example or two of enactive representation un-derlines its importance in infancy and in disturbedfunctioning, while illustrating its limitations. Piaget(1954) provides us with an observation from theclosing weeks of the first year of life. The child isplaying with a rattle in his crib. The rattle dropsover the side. The child moves his clenched handbefore his face, opens it, looks for the rattle. Notfinding it there, he moves his hand, closed again,back to the edge of the crib, shakes it with move-

COURSE OF COGNITIVE GROWTH

ments like those he uses in shaking the rattle. There-upon he moves his closed hand back toward his face,opens it, and looks. Again no rattle; and so hetries again. In several months, the child has bene-fited from experience to the degree that the rattleand action become separated. Whereas earlier hewould not show signs of missing the rattle when itwas removed unless he had begun reaching for it,now he cries and searches when the rattle is pre-sented for a moment and hidden by a cover. He nolonger repeats a movement to restore the rattle. Inplace of representation by action alone—where "ex-istence" is denned by the compass of present ac-tion—it is now denned by an image that persistsautonomously.

A second example is provided by the resultsof injury to the occipital and temporal cortex inman (Hanfmann, Rickers-Ovsiankina, & Goldstein,1944). A patient is presented with a hard-boiledegg intact in its shell, and asked what it is. Hold-ing it in his hand, he is embarrassed, for he can-not name it. He makes a motion as if to throw itand halts himself. Then he brings it to his mouthas if to bite it and stops before he gets there. Hebrings it to his ear and shakes it gently. He ispuzzled. The experimenter takes the egg from himand cracks it on the table, handing it back. Thepatient then begins to peel the egg and announceswhat it is. He cannot identify objects without ref-erence to the action he directs toward them.

The disadvantages of such a system are illus-trated by Emerson's (1931) experiment in whichchildren are told to place a ring on a board withseven rows and six columns of pegs, copying theposition of a ring put on an identical board by theexperimenter. Children ranging from 3 to 12 wereexamined in this experiment and in an extension ofit carried out by Werner (1948). The child's boardcould be placed in various positions relative to theexperimenter's: right next to it, 90 degrees rotatedaway from it, 180 degrees rotated, placed face toface with it so that the child has to turn full aroundto make his placement, etc. The older the child,the better his performance. But the younger chil-dren could do about as well as the oldest so longas they did not have to change their own positionvis-a-vis the experimenter's board in order to makea match on their own board. The more they hadto turn, the more difficult the task. They wereclearly depending upon their bodily orientation to-ward the experimenter's board to guide them. When

this orientation is disturbed by having to turn, theylose the position on the board. Older children suc-ceed even when they must turn, either by the useof imagery that is invariant across bodily displace-ments, or, later, by specifying column and row ofthe experimenter's ring and carrying the symbol-ized self-instruction back to their own board. It isa limited world, the world of enactive representa-tion.

We know little about the conditions necessary forthe growth of imagery and iconic representation, orto what extent parental or environmental interven-tion affects it during the earliest years. In ordi-nary adult learning a certain amount of motoricskill and practice seems to be a necessary precon-dition for the development of a simultaneous imageto represent the sequence of acts involved. If anadult subject is made to choose a path through acomplex bank of toggle switches, he does not forman image of the path, according to Mandler (1962),until he has mastered and overpracticed the taskby successive manipulation. Then, finally, he re-ports that an image of the path has developed andthat he is now using it rather than groping his waythrough.

Our main concern in what follows is not withthe growth of iconic representation, but with thetransition from it to symbolic representation. Forit is in the development of symbolic representationthat one finds, perhaps, the greatest thicket of psy-chological problems. The puzzle begins when thechild first achieves the use of productive grammar,usually late in the second year of life. Toward theend of the second year, the child is master of thesingle-word, agrammatical utterance, the so-calledholophrase. In the months following, there occursa profound change in the use of language. Twoclasses of words appear—a pivot class and an openclass—and the child launches forth on his careerin combinatorial talking and, perhaps, thinking.Whereas before, lexemes like allgone and mummyand sticky and bye-bye were used singly, now, forexample, allgone becomes a pivot word and is usedin combination. Mother washes jam off the child'shands; he says allgone sticky. In the next days, ifhis speech is carefully followed (Braine, 1963), itwill be apparent that he is trying out the limits ofthe pivot combinations, and one will even find con-structions that have an extraordinary capacity forrepresenting complex sequences—like allgone bye-bye after a visitor has departed. A recent and in-

AMERICAN PSYCHOLOGIST

Matrix Procedure

0 1 2 3 4 5 6i Scale in inches

FIG. 1. Array of glasses used in study of matrix ordering(Bruner & Kenney, in press).

genious observation by Weir (1962) on her 21-year-old son, recording his speech musings after hewas in bed with lights out, indicates that at thisstage there is a great deal of metalinguistic com-binatorial play with words in which the child isexploring the limits of grammatical productiveness.

In effect, language provides a means, not onlyfor representing experience, but also for transform-ing it. As Chomsky (19S7) and Miller (1962)have both made clear in the last few years, thetransformational rules of grammar provide a syn-tactic means of reworking the "realities" one hasencountered. Not only, if you will, did the dogbite the man, but the man was bitten by the dogand perhaps the man was not bitten by the dog orwas the man not bitten by the dog. The range ofreworking that is made possible even by the threetransformations of the passive, the negative, andthe query is very striking indeed. Or the orderingdevice whereby the comparative mode makes itpossible to connect what is heavy and what is lightinto the ordinal array of heavy and less heavy isagain striking. Or, to take a final example, there isthe discrimination that is made possible by thegrowth of attribute language such that the globaldimension big and little can now be decomposedinto tall and short on the one hand and jat andskinny on the other.

Once the child has succeeded in internalizing lan-guage as a cognitive instrument, it becomes possiblefor him to represent and systematically transformthe regularities of experience with far greater flexi-bility and power than before. Interestingly enough,it is the recent Russian literature, particularly

Vygotsky's (1962) book on language and thought,and the work of his disciple, Luria (1961), and hisstudents (Abramyan, 1958; Martsinovskaya, un-dated) that has highlighted these phenomena bycalling attention to the so-called second-signal sys-tem which replaces classical conditioning with aninternalized linguistic system for shaping and trans-forming experience itself.

If all these matters were not of such complexityand human import, I would apologize for taking somuch time in speculation. We turn now to somenew experiments designed to shed some light onthe nature of representation and particularly uponthe transition from its iconic to its symbolic form.

Let me begin with an experiment by Bruner andKenney (in press) on the manner in which childrenbetween S and 7 handle a double classificationmatrix. The materials of the experiment are nineplastic glasses, arranged so that they vary in 3degrees of diameter and 3 degrees of height. Theyare set before the child initially, as in Figure 1, ona 3 X 3 grid marked on a large piece of cardboard.To acquaint the child with the matrix, we first re-move one, then two, and then three glasses fromthe matrix, asking the child to replace them. Wealso ask the children to describe how the glasses inthe columns and rows are alike and how they differ.Then the glasses are scrambled and we ask thechild to make something like what was there be-fore by placing the glasses on the same grid thatwas used when the task was introduced. Now wescramble the glasses once more, but this time weplace the glass that was formerly in the southwestcorner of the grid in the southeast corner (it is theshortest, thinnest glass) and ask the child if he canmake something like what was there before, leav-ing the one glass where we have just put it. Thatis the experiment.

The results can be quickly told. To begin with,there is no difference between ages 5, 6, and 7 eitherin terms of ability to replace glasses taken fromthe matrix or in building a matrix once it hasbeen scrambled (but without the transposed glass).Virtually all the children succeed. Interestinglyenough, all the children rebuild the matrix to matchthe original, almost as if they were copying whatwas there before. The only difference is that theolder children are quicker.

Now compare the performance of the three agesin constructing the matrix with a single member

COURSE or COGNITIVE GROWTH

transposed. Most of the 7-year-olds succeed in thetransposed task, but hardly any of the youngestchildren. Figure 2 presents the results graphically.The youngest children seem to be dominated by animage of the original matrix. They try to put thetransposed glass "back where it belongs," to rotatethe cardboard so that "it will be like before," andsometimes they will start placing a few glassesneighboring the transposed glass correctly only torevert to the original arrangement. In several in-stances, 5- or 6-year-olds will simply try to recon-stitute the old matrix, building right over the trans-posed glass. The 7-year-old, on the other hand, ismore likely to pause, to treat the transposition asa problem, to talk to himself about "where thisshould go." The relation of place and size is forhim a problem that requires reckoning, not simplycopying.

Now consider the language children use for de-scribing the dimensions of the matrix. Recall thatthe children were asked how glasses in a row andin a column were alike and how they differed. Chil-dren answered in three distinctive linguistic modes.One was dimensional, singling out two ends of anattribute—for example, "That one is higher, andthat one is shorter." A second was global in na-ture. Of glasses differing only in height the childsays, "That one is bigger and that one is little."The same words could be used equally well fordiameter or for nearly any other magnitude. Fi-nally, there was conjounded usage: "That one istall and that one is little," where a dimensionalterm is used for one end of the continuum and aglobal term for the other. The children who used

8.0

6.0

3.0 -

Transposition

Reproduction

5 6 7Age

Reconstruction of Matrix

FIG. 2. Mean number of errors made by children in re-producing and transposing a 3 X 3 matrix (Bruner &Kenney, in press).

75

£ g 50

'*«III o 25

C - CompoundedG- GlobalD • Dimensional

C G D

Height

C G D

Diameter

Descriptive Language Use

FIG. 3. Percentage of children (aged 5-7) using differentlanguage patterns who reproduced transposed matrix error-lessly (Bruner & Kenney, in press).

confounded descriptions had the most difficultywith the transposed matrix. Lumping all ages to-gether, the children who used confounded descrip-tions were twice as likely to fail on the transposi-tion task as those who used either dimensional orglobal terms. But the language the children usedhad no relation whatsoever to their performance inreproducing the first untransposed matrix. Inhelderand Sinclair2 in a recent communication also re-port that confounded language of this kind is as-sociated with failure on conservation tasks in chil-dren of the same age, a subject to which we shallturn shortly.

The findings of this experiment suggest twothings. First, that children who use iconic repre-sentation are more highly sensitized to the spatial-qualitative organization of experience and less tothe ordering principles governing such organiza-tion. They can recognize and reproduce, but can-not produce new structures based on rule. Andsecond, there is a suspicion that the language theybring to bear on the task is insufficient as a toolfor ordering. If these notions are correct, then cer-tain things should follow. For one thing, improve-ment in language should aid this type of problemsolving, This remains to be investigated. But it isalso reasonable to suppose that activation of lan-guage habits that the child has already masteredmight improve performance as well—a hypothesisalready suggested by the findings of Luria's stu-dents (e.g., Abramyan, 1958). Now, activation canbe achieved by two means: One is by having the

2 Barbel Inhelder and Mimi Sinclair, personal communi-cation, 1963.

AMERICAN PSYCHOLOGIST

Conservation Tests

' i 1 1 ' i ' i ' Scale in incheso z* e e

Same Pour Slill Some?

Same Pour Still Same?

FIG. 4. Two Geneva tests for conservation of liquid vol-ume across transformations in its appearance (Piaget &Inhelder, 1962).

child "say" the description of something before himthat he must deal with symbolically. The other isto take advantage of the remoteness of referencethat is a feature of language, and have the child"say" his description in the absence of the thingsto be described. In this way, there would be lesslikelihood of a perceptual-iconic representation be-coming dominant and inhibiting the operation ofsymbolic processes. An experiment by FranchiseFrank (in press) illustrates this latter approach—the effects of saying before seeing.

Piaget and Inhelder (1962) have shown that ifchildren between ages 4 and 7 are presented twoidentical beakers which they judge equally full of

Screening Prediction and Feedback : Part HE

Original Mark level Pour into Mark level Unscreen andDisplay of woler empty glass of other glass ask explanation

, n i l . ,

water, they will no longer consider the water equalif the contents of one of the beakers is now pouredinto a beaker that is either wider or thinner thanthe original. If the second beaker is thinner, theywill say it has more to drink because the water ishigher; if the second beaker is wider, they will sayit has less because the water is lower. Comparableresults can be obtained by pouring the contents ofone glass into several smaller beakers. In Genevaterms, the child is not yet able to conserve liquidvolume across transformations in its appearance.Consider how this behavior can be altered.

Franchise Frank first did the classic conserva-tion tests to determine which children exhibitedconservation and which did not. Her subjects were4, 5, 6, and 7 years old. She then went on to other

FIG. 5. One procedure used in study of effect of languageactivation on conservation (Frank, in press).

Conservation and Screening

FIG. 6. Percentage of children showing conservation ofliquid volume before and during screening and upon un-screening of the displays (Frank, in press).

procedures, among which was the following. Twostandard beakers are partly filled so that the childjudges them to contain equal amounts of water. Awider beaker of the same height is introduced andthe three beakers are now, except for their tops,hidden by a screen. The experimenter pours froma standard beaker into the wider beaker. The child,without seeing the water, is asked which has moreto drink, or do they have the same amount, thestandard or the wider beaker. The results are inFigure 6. In comparison with the unscreened pre-test, there is a striking increase in correct equalityjudgments. Correct responses jump from 0% to50% among the 4s, from 20% to 9Q% among the5s, and from 50% to 100% among the 6s. Withthe screen present, most children justify their cor-

COURSE OF COGNITIVE GROWTH

rect judgment by noting that "It's the same wa-ter," or "You only poured it."

Now the screen is removed. All the 4-year-oldschange their minds. The perceptual display over-whelms them and they decide that the wider beakerhas less water. But virtually all of the 5-year-oldsstick to their judgment, often invoking the differ-ence between appearance and reality—"It lookslike more to drink, but it is only the same becauseit is the same water and it was only poured fromthere to there," to quote one typical S-year-old.And all of the 6s and all the 7s stick to their judg-ment. Now, some minutes later, Frank does aposttest on the children using a tall thin beakeralong with the standard ones, and no screen, ofcourse. The 4s are unaffected by their prior ex-perience: None of them is able to grasp the idea ofinvariant quantity in the new task. With the 5s,instead of 20% showing conservation, as in the pre-test, 70% do. With both 6s and 7s, conservationincreases from 50% to 90%. I should mention thatcontrol groups doing just a pretest and posttestshow no significant improvement in performance.

A related experiment of Nair's (1963) exploresthe arguments children use when they solve a con-servation task correctly and when they do not. Hersubjects were all 5-year-olds. She transferred wa-ter from one rectangular clear plastic tank to an-other that was both longer and wider than the first.Ordinarily, a 5-year-old will say there is less waterin the second tank. The water is, of course, lowerin the second tank. She had a toy duck swimmingin the first container, and when the water waspoured into the new container, she told the childthat "The duck was taking his water with him."

Three kinds of arguments were set forth by thechildren to support their judgments. One is per-ceptual—having to do with the height, width, orapparent "bigness" of the water. A second typehas to do with action: The duck took the wateralong, or the water was only poured. A third one,"transformational" argument, invokes the reversi-bility principle: If you poured the water back intothe first container, it would look the same again.3

Of the children who thought the water was not

3 Not one of the 40 children who participated in this ex-periment used the compensation argument—that thoughthe water was lower it was correspondingly wider and was,therefore, the same amount of water. This type of rea-soning by compensation is said by Piaget and Inhelder(1962) to be the basis of conservation.

100

80

60

20

Age

After-Effects of Screening

FIG. 7. Percentage of children showing conservation ofliquid volume in identical pretest and posttest run aftercompletion of experiment (Frank, in press).

equal in amount after pouring, 15% used nonper-ceptual arguments to justify their judgment. Ofthose who recognized the equality of the water,two-thirds used nonperceptual arguments. It isplain that if a child is to succeed in the conserva-tion task, he must have some internalized verbalformula that shields him from the overpoweringappearance of the visual displays much as in theFrank experiment. The explanations of the chil-dren who lacked conservation suggest how stronglyoriented they were to the visual appearance of thedisplays they had to deal with.

Consider now another experiment by Bruner andKenney (in press) also designed to explore theborder between iconic and symbolic representation.Children aged 5, 6, and 7 were asked to say whichof two glasses in a pair was fuller and whichemptier. "Fullness" is an interesting concept towork with, for it involves in its very definition aratio or proportion between the volume of a con-tainer and the volume of a substance contained.It is difficult for the ironically oriented child to seea half-full barrel and a half-filled thimble as equallyfull, since the former looms larger in every one ofthe attributes that might be perceptually associ-ated with volume. It is like the old riddle of whichis heavier, a pound of lead or a pound of feathers.To make a correct judgment of fullness or empti-ness, the child must use a symbolic operation, some-what like computing a ratio, and resist the tempta-tion to use perceptual appearance—that is, unlesshe finds some happy heuristic to save him the la-bor of such a computation. Figure 8 contains the

AMERICAN PSYCHOLOGIST

Ratio Procedure

FIG. 8. Eleven pairs of glasses to be judged in terms ofwhich glass is fuller and which emptier (Bruner & Kenney,in press).

11 pairs of glasses used, and they were selectedwith a certain malice aforethought.

There are four types of pairs. In Type I (Dis-plays 4, 9a, and 9b), the glasses are of unequalvolume, but equally, though fractionally, full. InType II (Displays 2, 7a, and 7b) again the glassesare of unequal volume, but they are completelyfull. Type III (Displays 3, 8a, and 8b) consistsof two glasses of unequal volume, one filled and theother part filled. Type IV consists of identicalglasses, in one case equally filled, in another un-equally (Displays 1 and 5).

All the children in the age range we have studieduse pretty much the same criteria for judging full-ness, and these criteria are based on directly ob-servable sensory indices rather than upon propor-

tion. That glass is judged fuller that has thegreater apparent volume of water, and the favoredindication of greater volume is water level; orwhere that is equated, then width of glass will do;and when width and water level are the same, thenheight of glass will prevail. But now consider thejudgments made by the three age groups with re-spect to which glass in each pair is emptier. Theolder children have developed an interesting con-sistency based on an appreciation of the comple-mentary relation of filled and empty space—albeitan incorrect one. For them "emptier" means theglass that has the largest apparent volume of un-filled space, just as "fuller" meant the glass thathad the largest volume of filled space. In conse-quence, their responses seem logically contradic-tory. For the glass that is judged fuller also turnsout to be the glass that is judged emptier—given alarge glass and a small glass, both half full. Theyounger children, on the other hand, equate empti-ness with "littleness": That glass is emptier thatgives the impression of being smaller in volume ofliquid. If we take the three pairs of glasses ofType I (unequal volumes, half filled) we can seehow the judgments typically distribute themselves.Consider only the errors. The glass with the largervolume of empty space is called emptier by 27%of the erring S-year-olds, by 53% of the erring 6-year-olds, and by 72% of erring 7-year-olds. Butthe glass with the smallest volume of water is calledemptier by 73% of the S-year-olds who err, 47%of the 6s, and only 28% of the 7s. When the chil-dren are asked for their reasons for judging oneglass as emptier, there is further confirmation:Most of the younger children justify it by pointing

TABLE 1PERCENTAGE OP ERRONEOUS JUDGMENTS OP WHICH OP Two

GLASSES is EMPTIER BASED ON Two CRITERIAFOR DEFINING THE CONCEPT

Criterion for "emptier"

Greater empty spaceSmaller volume of liquid

Percentage correct# =

Age

5

27%73%

100%

9%30

6

53%47%

100%

8%30

7

72%28%

100%

17%30

Note.—Criteria are greater volume of empty space and lesserjvolumeof water. From Bruner and Kenney (in press).

COURSE OF COGNITIVE GROWTH

100

so

60

40ui

20

Contradiction

Plain Error

5 6 7

Age

Proportion ofTwo Types of Error

FIG. 9. Percentage of children at three ages who makecontradictory and plain errors in judging which of twoglasses is fuller and which emptier. (A contradictory erroris calling the same glass both fuller or emptier or callingthem equally full but not equally empty or vice versa. Aplain error is calling one glass fuller and the other emptier,but incorrectly. From Bruner & Kenney, in press.)

to "littleness" or "less water" or some other aspectof diminutiveness. And most of the older childrenjustify their judgments of emptiness by referenceto the amount of empty space in the vessel.

The result of all this is, of course, that the "logi-cal structure" of the older children seems to go in-creasingly awry. But surely, though Figure 9 showsthat contradictory errors steadily increase with age(calling the same glass fuller and emptier or equallyfull but not equally empty or vice versa), the con-tradiction is a by-product of the method of dealingwith attributes. How shall we interpret these find-ings? Let me suggest that what is involved is atranslation difficulty in going from the perceptualor iconic realm to the symbolic. If you ask chil-dren of this age whether something can be fullerand also emptier, they will smile and think thatyou are playing riddles. They are aware of thecontrastive nature of the two terms. Indeed, eventhe very young child has a good working languagefor the two poles of the contrast: "all gone" forcompletely empty and "spill" or "tippy top" forcompletely full. Recall too that from 5 to 7, thereis perfect performance in judging which of twoidentical beakers is fuller and emptier. The differ-ence between the younger and the older child is inthe number of attributes that are being attendedto in situations involving fullness and emptiness:The younger child is attending to one—the volume

of water; the older to two—the volume of filledspace and the volume of empty space. The youngchild is applying a single contrast pair—full-empty—to a single feature of the situation. The olderchild can attend to two features, but he does notyet have the means for relating them to a third, thevolume of the container per se. To do so involvesbeing able to deal with a relation in the perceptualfield that does not have a "point-at-able" or osten-sive definition. Once the third term is introduced—the volume of the glass—then the symbolic conceptof proportion can come to "stand for" somethingthat is not present perceptually. The older childis on the way to achieving the insight, in spite ofhis contradictions. And, interestingly enough, ifwe count the number of children who justify theirjudgments of fuller and emptier by pointing toseveral rather than a single attribute, we find thatthe proportion triples in both cases between age 5and age 7. The older child, it would seem, is order-ing his perceptual world in such a way that, shortly,he will be able to apply concepts of relationshipthat are not dependent upon simple ostensive defi-nition. As he moves toward this more powerful"technology of reckoning," he is led into errorsthat seem to be contradictory. What is particu-larly telltale is the fact, for example, that in theType III displays, younger children sometimesseem to find the judgment easier than older chil-dren—pointing to the fuller by placing their fingeron the rim of the full member and pointing to theemptier with the remark that "It is not to the top."The older child (and virtually never the youngerone) gets all involved in the judgment of "fuller byapparent filled volume" and then equally involvedin the judgment of "emptier by apparent emptyvolume" and such are his efforts that he fails tonote his contradiction when dealing with a pairlike Display 8b.

Turn now to a quite different experimental pro-

TABLE 2

PERCENTAGE ot CHILDREN WHO JUSTIFY JUDGMENTS OF"FULLER" AND "EMPTIER" BY MENTIONING MORE

THAN A SINGLE ATTRIBUTE

Age

567

"Fuller-judgments

7.2%15.6%22.2%

"Emptier"judgments

4.1%9.3%

15.6%

N

303030

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100

80

S£ 60is

-o £:_ 5

20 h

,To1Ql Functioned

Arbitrary Functional

Perceptual

9

Age

Attributes Used in Grouping

FIG. 10. Features of objects used by children of differ-ent ages as a basis for placing the objects in equivalencegroups (Olver, 1961).

cedure that deals with the related concept ofequivalence—how seemingly different objects aregrouped into equivalence classes. In the two ex-periments to be cited, one by Olver (1961), theother by Rigney (1962), children are given wordsor pictures to sort into groups or to characterize interms of how they are alike. The two sets of re-sults, one for words, the other for pictures, ob-tained for children between 6 and 14, can be sum-marized together. One may distinguish two aspectsof grouping—the first has to do with the featuresor attributes that children use as a criterion forgrouping objects: perceptual features (the color,size, pattern, etc.), arbitrary functional features(what I can do with the objects regardless of theirusual use: You can make noise with a newspaperby crumpling it and with a book by slamming itshut, etc.), appropriate functional features (potato,peach, banana, and milk are characterized "You caneat them"). But grouping behavior can also becharacterized in terms of the syntactical structureof the equivalence sets that the child develops.There are, first, what Vygotsky (1962) has calledheaps: collections put together in an arbitrary waysimply because the child has decided to put themtogether that way. Then there are complexes: Thevarious members of a complex are included in theclass in accordance with a rule that does not ac-count uniformly for the inclusion of all the mem-bers. Edge matching is one such rule: Each ob-ject is grouped into a class on the basis of itssimilarity with a neighboring object. Yet no twoneighboring pieces may be joined by the same simi-

larity. Another type of complexive grouping isthematic: Here objects are put together by virtueof participating in a sentence or a little story.More sophisticated is a key ring in which one or-ganizing object is related to all others but none ofthose to each other. And finally, considerably moresophisticated than heaps and complexes, there aresuperordinate concepts, in which one universal ruleof inclusion accounts for all the objects in the set—all men and women over 21 are included in the classof voters provided they meet certain residence re-quirements.

The pattern of growth is revealing of many ofthe trends we have already discussed, and providesin addition a new clue. Consider first the attributesor features of objects that children at different agesuse as a basis for forming equivalence groups. AsFigure 10 indicates, the youngest children rely moreheavily on perceptual attributes than do the others.As they grow older, grouping comes to depend in-creasingly upon the functional properties of things—but the transitional phase is worth some atten-tion, for it raises anew the issue of the significanceof egocentrism. For the first functional groupingsto appear are of an arbitrary type—what "I" or"you" can do to objects that renders them alike,rather than what is the conventional use or func-tion to which objects can be put. During thisstage of "egocentric functionalism," there is a cor-responding rise in the use of first- and second-per-son personal pronouns: "I can do thus and so tothis object; I can do the same to this one," etc.Gradually, with increasing maturity the child shiftsto an appropriate and less egocentric form of using

Two Types of Grouping Strategies

FIG. 11. The use of two rules of equivalence groupingfound in children of different ages (Olver, 1961).

COURSE OF COGNITIVE GROWTH 11

functional groupings. The shift from perceptual tofunctional groupings is accompanied by a corre-sponding shift in the syntactical structure of thegroups formed. Complexive groupings steadilydwindle; superordinate groupings rise, until thelatter almost replace the former in late adolescence.It is difficult to tell which is the pacemaker in thisgrowth—syntax or the semantic basis of grouping.

Rigney reports one other matter of some inter-est. Her young subjects formed groups of any sizethey wished, choosing pictures from a displayboard of several dozen little water colors. She ob-served that the most perceptually based groupsand the ones most often based on complexivegrouping principles were pairs. A count of theserevealed that 61% of all the groups made by 6-year-olds were such pairs, 36% of those made by8-year-olds, and only 25% of the groupings of 11-year-olds.

On the surface, this set of findings—Giver's andRigney's alike—seems to point more to the declineof a preference for perceptual and iconic ways ofdealing with objects and events, particularly withtheir grouping. But closer inspection suggests stillanother factor that is operating. In both cases,there is evidence of the development of hierarchicalstructure and rules for including objects in super-ordinate hierarchies. Hierarchical classification issurely one of the most evident properties of thestructure of language—hierarchical grouping thatgoes beyond mere perceptual inclusion. Complexivestructures of the kind described earlier are muchmore dominated by the sorts of associative prin-ciples by which the appearance of objects leads totheir spontaneous grouping in terms of similarityor contiguity. As language becomes more inter-nalized, more guiding as a set of rules for organiz-ing events, there is a shift from the associative prin-ciples that operate in classical perceptual organiza-tion to the increasingly abstract rules for groupingevents by the principles of inclusion, exclusion, andoverlap, the most basic characteristics of any hier-archical system.

We have said that cognitive growth consists inpart in the development of systems of representa-tion as means for dealing with information. Thegrowing child begins with a strong reliance uponlearned action patterns to represent the worldaround him. In time, there is added to this tech-nology a means for simultanizing regularities in ex-perience into images that stand for events in the

way that pictures do. And to this is finally addeda technology of translating experience into a sym-bol system that can be operated upon by rules oftransformation that greatly increase the possiblerange of problem solving. One of the effects of thisdevelopment, or possibly one of its causes, is thepower for organizing acts of information processinginto more integrated and long-range problem solv-ing efforts. To this matter we turn next.

Consider in rapid succession three related experi-ments. All of them point, I think, to the same con-clusion.

The first is by Huttenlocher (in press), a strik-ingly simple study, performed with children be-tween the ages of 6 and 12. Two light switches arebefore the child; each can be in one of two posi-tions. A light bulb is also visible. The child isasked to tell, on the basis of turning only oneswitch, what turns the light on. There are fourways in which the presentations are made. In thefirst, the light is off initially and when the childturns a switch, the light comes on. In the second,the light is on and when the child turns a switch,it goes off. In the third, the light is on and whenthe child turns a switch, it stays on. In the fourthand final condition, the light is off and when thechild turns a switch, it stays off. Now what is in-triguing about this arrangement is that there aredifferent numbers of inductive steps required tomake a correct inference in each task. The sim-plest condition is the off-on case. The position towhich the switch has just been moved is respon-sible for the light going on. Intermediate difficultyshould be experienced with the on-off condition. Inthe on-off case, two connected inferences are re-quired: The present position achieved is rejectedand the original position of the switch that hasbeen turned is responsible for lighting the bulb. Aneven larger number of consecutive acts is requiredfor success in the on-on case: The present positionof the turned switch is rejected, the original posi-tion as well and the present position of the otherswitch is responsible. The off-off case requires foursteps: rejecting the present position of the turnedswitch, its original position, and the present posi-tion of the other switch, finally accepting the al-ternative position of the unturned switch. The na-tures of the individual steps are all the same. Suc-cess in the more complex cases depends upon beingable to integrate them consecutively.

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40

Age

Use of Connected Questionsin Twenty Questions Game

Fio. 12. The proportion of children at different ageswho use connected questions in a Twenty Questions game(Mosher, 1962).

Huttenlocher's results show that the 6-year-oldsare just as capable as their elders of performingthe elementary operation involved in the one-stepcase: the on-off display. They, like the 9s and12s, make nearly perfect scores. But in general,the more inferential steps the 6-year-old mustmake, the poorer his performance. By age 12, onthe other hand, there is an insignificant differencebetween the tasks requiring one, two, three, or fourconnected inferences.

An experiment by Mosher (1962) underlines thesame point. He was concerned with the strategiesused by children from 6 to 11 for getting informa-tion in the game of Twenty Questions. They wereto find out by "yes-no" questions what caused acar to go off the road and hit a tree. One maydistinguish between connected constraint-locatingquestions ("Was it night-time?" followed up ap-propriately) and direct hypothesis-testing questions("Did a bee fly in the window and sting the manon the eye and make him go off the road and hitthe tree?"). From 6 to 11, more and more chil-dren use constraint-locating, connected questioning.Let me quote from Mosher's account.

We have asked children . . . after they have played theirgames, to tell us which of two questions they would ratherhave the answer to, if they were playing the games again—one of them a typical constraint-seeking question ("Wasthere anything wrong with the man?") and the other atypical discrete test of an hypothesis ("Did the man havea heart attack?"). All the eleven-year-olds and all theeight-year-olds choose the constraint-seeking question, butonly 29% of the six-year-olds do [p. 6].

The questions of the younger children are allone-step substitutes for direct sense experience.They are looking for knowledge by single ques-tions that provide the answer in a finished form.When they succeed they do so by a lucky ques-tion that hits an immediate, perceptible cause.When the older child receives a "yes" answer toone of his constraint-locating questions, he mostoften follows up by asking another. When, on therare occasions that a younger child asks a con-straint question and it is answered "yes," he almostinvariably follows it up with a specific question totest a concrete hypothesis. The older child canaccrete his information in a structure governed byconsecutive inference. The younger child cannot.

Potter's (in press) study of the development ofperceptual recognition bears on the same point.Ordinary colored photographs of familiar scenesare presented to children between 6 and 12, thepictures coming gradually into focus. Let me sumup one part of the results very briefly. Six-year-olds produce an abundance of hypotheses. Butthey rarely try to match new hypotheses to previ-ous ones. "There is a big tower in the middle anda road over there and a big ice cream cone throughthe middle of the tower and a pumpkin on top."It is like a random collage. The 9-year-old's tor-rent of hypotheses, on the other hand, shows asense of consistency about what is likely to appearwith what. Things are in a context of likelihood,a frame of reference that demands internal consist-ency. Something is seen as a merry-go-round, andthe child then restricts later hypotheses to theother things to be found in an amusement park.The adolescent operates under even more highlyorganized sequential constraints: He occasionallydevelops his initial hypotheses from what is im-plied by the properties of the picture, almost byintersection—"It is red and shiny and metallic: Itmust be a coffee-pot." Once such constraints areestablished, the order of hypotheses reflects evenmore the need to build up a consistent world of ob-jects—even to the point of failing to recognizethings that do not fit it.

What shall we make of these three sets of find-ings—that older children are able to cumulate in-formation by asking questions in a directed se-quence leading to a final goal, and that they arecapable of recognizing visual displays in a mannergoverned by a dominating frame of reference thattranscends momentary and isolated bits of infor-

COUESE OF COGNITIVE GROWTH 13

mation? Several points seem apparent. The firstis that as children mature, they are able to use in-direct information based on forms of informationprocessing other than the act of pointing to whatis immediately present. They seem, in short, tomake remote reference to states and constraintsthat are not given by the immediate situation, togo beyond the information given. Second, and thisis a matter that has already been discussed, theyseem to be able to cumulate information into astructure that can be operated upon by rules thattranscend simple association by similarity and con-tiguity. In the case of Twenty Questions, the ruleis best described as implication—that knowing onething implies certain other things and eliminatesstill others. In the experiments with the lightswitches, it is that if the present state does notproduce the effect, then there is a system for trac-ing back to the other states that cause the light togo on. Where perceptual recognition is concerned,the rule is that a piece of information from onepart of the display implies what other parts mightbe. The child, in sum, is translating redundancyinto a manipulable model of the environment thatis governed by rules of implication. It is this modelof the environment that permits him to go beyondthe information before him. I would suggest thatit is this new array of cognitive equipment thatpermits the child to transcend momentaneity, tointegrate longer sequences of events.

Let me urge, moreover, that such a system ofprocessing environmental events depends upon thetranslation of experience into symbolic form.Such a translation is necessary in order for thereto be the kind of remoteness of reference as is re-quired when one deals with indirect information.To transcend the immediately perceptual, to getbeyond what is vividly present to a more extendedmodel of the environment, the child needs a sys-tem that permits him to deal with the nonpresent,with things that are remote in space, qualitativesimilarity, and time, from the present situation.Hockett (19S9), in describing the design featuresof language includes this feature as crucial. He isreferring to human speech as a system of com-munication. The same point can be made aboutlanguage as an instrument of thought. That hu-mans have the capacity for using speech in thisway is only part of the point. What is critical isthat the capacity is not used until it is coupled

with the technology of language in the cognitiveoperations of the child.

The same can be said for the models of the en-vironment that the child constructs to go beyondpresent information. This is not to say that non-verbal animals cannot make inferences that go be-yond the present stimulus: Anticipatory activity isthe rule in vertebrates. But the models that thegrowing child constructs seem not to be antici-patory, or inferential, or probabilistic-frequencymodels. They seem to be governed by rules thatcan more properly be called syntactical rather thanassociative.

My major concern has been to examine afreshthe nature of intellectual growth. The account hassurely done violence to the richness of the subject.It seems to me that growth depends upon the emer-gence of two forms of competence. Children, asthey grow, must acquire ways of representing therecurrent regularities in their environment, andthey must transcend the momentary by developingways of linking past to present to future—repre-sentation and integration. I have suggested thatwe can conceive of growth in both of these domainsas the emergence of new technologies for the un-locking and amplification of human intellectualpowers. Like the growth of technology, the growthof intellect is not smoothly monotonic. Rather, itmoves forward in spurts as innovations are adopted.Most of the innovations are transmitted to the childin some prototypic form by agents of the culture:ways of responding, ways of looking and imaging,and most important, ways of translating what onehas encountered into language.

I have relied heavily in this account on the suc-cessive emergence of action, image, and word asthe vehicles of representation, a reliance basedboth upon our observations and upon modern read-ings of man's alloplastic evolution. Our attentionhas been directed largely to the transition betweeniconic and symbolic representation.

In children between 4 and 12 language comes toplay an increasingly powerful role as an implementof knowing. Through simple experiments, I havetried to show how language shapes, augments, andeven supercedes the child's earlier modes of proc-essing information. Translation of experience intosymbolic form, with its attendant means of achiev-ing remote reference, transformation, and combina-tion, opens up realms of intellectual possibility that

14 AMERICAN PSYCHOLOGIST

are orders of magnitude beyond the most powerfulimage forming system.

What of the integration of intellectual activityinto more coherent and interconnected acts? It hasbeen the fashion, since Freud, to see delay of grati-fication as the principal dynamism behind this de-velopment—from primary process to secondaryprocess, or from assimilation to accommodation, asPiaget would put it today. Without intending toquestion the depth of this insight, let me suggestthat delay of immediate gratification, the abilityto go beyond the moment, also depends upon tech-niques, and again they are techniques of repre-sentation. Perhaps representation exclusively byimagery and perceptual organization has built intoit one basic operation that ties it to the immediatepresent. It is the operation of pointing—ostensive-ness, as logicians call it. (This is not to say thathighly evolved images do not go beyond immediatetime and given place. Maps and flow charts areiconic in nature, but they are images that trans-late prior linguistic and mathematical renderingsinto a visual form.) Iconic representation, in thebeginning, is build upon a perceptual organizationthat is tied to the "point-at-able" spatioqualitativeproperties of events. I have suggested that, forall its limitations, such representation is an achieve-ment beyond the earlier stage where percepts arenot autonomous of action. But so long as percep-tual representation dominates, it is difficult to de-velop higher-order techniques for processing infor-mation by consecutive inferential steps that takeone beyond what can be pointed at.

Once language becomes a medium for the trans-lation of experience, there is a progressive releasefrom immediacy. For language, as we have com-mented, has the new and powerful features of re-moteness and arbitrariness: It permits productive,combinatorial operations in the absence of what isrepresented. With this achievement, the child candelay gratification by virtue of representing to him-self what lies beyond the present, what other pos-sibilities exist beyond the clue that is under hisnose. The child may be ready for delay of gratifi-cation, but he is no more able to bring it off thansomebody ready to build a house, save that he hasnot yet heard of tools.

The discussion leaves two obvious questions beg-ging. What of the integration of behavior in or-ganisms without language? And how does languagebecome internalized as a vehicle for organizing ex-

perience? The first question has to be answeredbriefly and somewhat cryptically. Wherever inte-grated behavior has been studied—as in Lehrman's(1955) careful work on integrated instinctive pat-terns in the ringdove, it has turned out that a sus-taining external stimulus was needed to keep thehighly integrated behavior going. The best way tocontrol behavior in subhuman species is to controlthe stimulus situation. Surely this is the lesson ofLashley's (1938) classic account of instinctive be-havior. Where animal learning is concerned, par-ticularly in the primates, there is, to be sure, con-siderable plasticity. But it too depends upon thedevelopment of complex forms of stimulus substi-tution and organization—as in Kluver's (1933)work on equivalence reactions in monkeys. If itshould seem that I am urging that the growth ofsymbolic functioning links a unique set of powersto man's capacity, the appearance is quite as itshould be.

As for how language becomes internalized as aprogram for ordering experience, I join those whodespair for an answer. My speculation, for what-ever it is worth, is that the process of internaliza-tion depends upon interaction with others, uponthe need to develop corresponding categories andtransformations for communal action. It is theneed for cognitive coin that can be exchanged withthose on whom we depend. What Roger Brown(1958) has called the Original Word Game endsup by being the Human Thinking Game.

If I have seemed to underemphasize the impor-tance of inner capacities—for example, the capacityfor language or for imagery—it is because I be-lieve that this part of the story is given by the na-ture of man's evolution. What is significant aboutthe growth of mind in the child is to what degreeit depends not upon capacity but upon the unlock-ing of capacity by techniques that come from ex-posure to the specialized environment of a culture.Romantic cliches, like "the veneer of culture" or"natural man," are as misleading if not as damag-ing as the view that the course of human develop-ment can be viewed independently of the educa-tional process we arrange to make that develop-ment possible.

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