HYPOTHESESCONCERNING

THE NRTUREOf INCUBATION

J. P. GUILFORD

Some Incubated Thoughtson Incubation

There can be no doubt that mental incubation is a genuine phe­nomenon and that it plays important roles in creative problemsolving. This is true despite the fact that only one of the well-knownwriters who have presented lists of the major steps in problemsolving or in creative thinking has explicitly included it as a majorstep, and that writer is Graham Wallas (1926). The writers on thesesubjects, however, have often mentioned anecdotes about crea­tive events in which incubation has played parts.

Before going further, a definition is in order. In the discussionsthat follow, incubation will mean a period in the behavior of theindividual during tvhich there is no apparent activity'on his parttoward the solution of a problem, but during which or at the endof which there are definite signs of further attempts, with some­times material progress toward 8; solution. During the intervalthe individual may have spontaneous glimpses of that activity.The period of incubation may be a matter of minutes or hours..even days, months, or years.The signs ofaction during the intervalcall for explanation.

Probably the oldest theory of incubation, going back at least asfar as Poincare, lsthat an "unconscious mind" is working on theproblem after the conscious mind has laid it aside. There seemseven to be an implication that the unconscious mind is superiorto the conscious mind in solving problems. Crediting inspirationsduring incubation to an unconscious mind tells us only thatmuch, besides im70lving us in an animistic conception, and leavingus with everything else to be explained. We would still not knowthe nature of incubation. We would not know what is going on.

Not being aware of the steps by which an inspired idea comes,there is the natural implication that it comes from somewhere

Volume 13 Number 1 Rrst Quarter

2

Some bicubated Thoughts on IncUbation

else. Some may go so far as to attribute such ideas to ESP. It ismost likely, of course, that the thinker's own brain is doing the job,and it is hard to see why anyone would not want to give his ownbrain the credit to which it is entitled,

There is a fatigue theory, to the effect that the thinker works onhis problem until he becomes tired, even exhausted, and the in­cubation period merely gives him time to rest.This theory can bereadily discounted for two reasons. One is that incubation may beeffective even if the thinker is busy working on something else. Itis therefore not a matter of recovering from general fatigue. Iffatigue is at aU a feature, it is very specific. But the fatigue theoryalso does not account for the fact that incubation periods oftenlast well beyond the time needed for recovery from fatigue, eithergeneral or specific.

Woodworth (1938) suggested that retLiming to a problem aftera period of incubation is favorable for the emergence of new ideasbecause, for one thing, it is a fresh.start, which maymean a revisedapproach to the problem. Incidental to this kind of event is the factthat the wrong or useless ideas that were brouqht up on the pre­vious occasion have lost their recency value, and therefore do notinterfere with the emergence of new ideas.

The two theories just mentioned pertain to the benefitsofhavinga period with no attention given to the problem, butdo notaccountfor the spontaneous emergence of ideas that occur withoutreturning to the problem. Incubated thoughts are known toemerge spontaneously in the midst of other activity or in statesof relaxation or rest. My own hypothesis is aimed at accounting forthe actual progress during an apparently inactive incubation inter­val. It attributes progress of this kind to transformations of infor­mation, very largely.

As background for this theory, let us consider what the problemsolver is doing psychologically. Let us assume that he has seenthat a problem exists and that he has structured it, and he is in theperiod of thinking of alternative solutions, or steps toward solution.At this point he is like the person who is in the act of taking a testfor one of the divergent-production abilities. He is retrieving fromhis memory store a sequence of items of information, under thesomewhat general control of his"search mode!." A search modelis composed of the specifications, as he sees it, for the solution tothe problem.

When human subjects are given simple recall tasks, such asthose calling for the names of flowers, foods, or cities ofthe U.SA.,a mathematical-functional relation is often found to apply, relatingrate of production items to the time from the starting point, asillustrated in Agure 1. The function shows a declining rate that

wfiG

URE

1A

func

tiona

lrel

atio

nshl

pbe

twee

np

rod

uct

ion

,inv

olvi

ngre

trie

valo

fite

ms

ofi

nfo

rma

tio

nfr

om

the

me

mo

ryst

ore,

and

wo

rkin

gti

me. ...

.--

I--

- - - - - r--

nn

nn

II

II

I

1 I ~ :! -o .. fl)

.D e :) z

10 5

510

.15

20

TIM

EIN

TERV

AtS

2530

~ c.. 8 [ ~ ~ f i

4

Some Incubated Thoughts on Incubation

becomes asymptotic to zero. The same kind of function appliesto the results from a test of divergent production, for example, atest of Plot Titles or of Unusual Uses '(Christensen, Guilford, &Wilson, 1957; Parnes, 1961). Of special note here is the fact thatif the task is continued long enough. there are short intervals inwhich no responses at all occur. The single responses that dooccur from time to time come at longer and longer intervals. Onecan readily imagine a similar picture extending beyond the termi­nation of the task, When an incubation period begins.

There is another important angle to the relation of productionto time. In both investigations in the two sources just cited, theexaminees' responses were evaluatedasto quality, and qualitywasexamined in connection with time. In the Christensen studies,responses were evaluated in terms of uniqueness or statisticalinfrequency, or as to remoteness of connection, or as to judgedcleverness. All of these indices had previously been found to beindicators of originality. In the Parnes study-responses were ratedfor unusualness or for usefulness. In all cases, the results werethe same. The further along in time from the beginning of the task,the more likely the response is found to be of high quality.

The general picture is one of the individual's getting his well­known and probably his less successful and less imaginative re­sponses, those"off the top of his head;' out of the way first. Thenhe is more free to search or must search in unusual directions forresponses that will do better or otherwise be more acceptable.The higher-quality responses that come then are more likely toinvolve transformations, which have become recognized as animportant secret of originality. It may well be that, normally, trans­formations require more time for the brain to produce. Or the brainwill not so perform unless it proves to be necessary.The period ofincubation provides that time. It should also be said that the trans­formations may occur in the conception of the problem as wellas in generating alternative solutions.

This line of thinking calls for the occurrence of unconscioustransformations. There is some evidence that such events dooccur. Studies of Davis and Sinha (l950a, b) have demonstratedthat items of information in memory storage are not immunefrom interactions with new inputs of information. They may be­come modified, that is to say, transformed. There is also the pos­sibility of interactions between items already stored, especiallyunder the pressures from motivational sources.Weiner (1966) hasassembled evidence to indicate the influence of motivation onmemory traces; on items in memory storage.

The last statement brings motivation into the picture. I thinkthat

5

PERSONRlITYTRAITS BNDINCUBATION

The Journal of Creative Behavior

it can be safely said that without a continued desire to solve theproblem there is little likelihood of incubation effects.An unsolvedproblem can leavea more or less painful void that must be filled,and this could put pressure on the brain parts that are responsiblefor meeting the challenge.

It is very likely that individuals differ considerably with respect tomotivation to solve problems, which brings us to a question ofpersonality. Some individuals may more readily close the matterof a problem, while others keep the matter open; fhey do not soreadily achieve closure. Early closure may mean accepting aninadequate or unjustified solution, or it may mean a dodging ona rejection of the problem. Leaving the gap open invites incuba­tion, and its openness may persist for a long time. Lack of closure,in a sense, means that the individual is continuing to try to solvethe problem. Without this persisting motivation it is likely thatlittle progress would be made toward solution. Also, under thiscondition of motivation, which can rise and fall, new input fromthe environment may interact with stored information to set offthe Eureka spark.

Spearman (1927) once proposed a very general trait of per­severation. Some persons, he said, are perseverators and someare not, more or less. He also proposed that the trait contributesto creativeness, perseveratorsbeing more creative.But experiencehas shown that perseveration takes different forms (Guilford,1959). Not all such traits would contribute to inclination towardincubation or success in incubation in problem solving. Forexample, some instances of perseveration are a mere reliving ofa recent vivid experience.

Highly creative people, among whom there is at least a highproportion of incubators, are often described as being introverted.This probably means introversion of one particular type - thinkingintroversion, a general tendency for reflectiveness. Reflectionmeans a pause in action, with the person perhaps going into aperiod of incubation. This description is reminiscent of Heid­breder's (1924) distinguishing of two types of problem solvers- the participators and the spectators. Some wade in and grapplewith the problem while others sit back and watch what happens.The latter may be expected among the incubators.

In general, it is known that the recall of items of information, theretrieval from memory storage, is facilitated by a state of relaxedeffort. We can often defeat recall by trying too hard. A generallyrelaxed state may also be helpful, since it has been noted thatincubated ideas often well up when the person is in a relaxedinter­val, perhaps on wakening from sleep. But it is unlikely that

6

Some Incubated Thoughts on Incubation

relaxation alone is sufficient; persistent motivation is probablynecessary.

Yet to be considered is the relation of a trait, or traits, of flexi·bility to ·incubation. There is sufficient evidence to reject the ideaof a universal trait of flexibility. There are known to be severalsuchtraits, some of them in the area of intellectual abilities or functions.It may be said that all of the divergent-production abilities repre­sent their special kinds of flexibility, for they are concemed withthe production of altematives. One type of rigid thinker is stuckwith only a single idea. The incubator is prepared to tolerate, infact to look for, other ideas, otherwise he would not be botheringto keep on solving problems.

Other kinds of flexibility are concemed with transformations.Being flexible in this sense is a readinessto modify or revise itemsof information. There are many abilities or functions involvingtransformations, and they appear in connection with kinds. ofmental operations other than divergent production - cognition,evaluation, and even convergent production. Assuming that aperson who is higher with respect to certain functions is also morelikely to indulge in their use, the individual who is strong in trans­formation abilities should be expected to employ them more, asin periods of incubation.

While we are considering personality traits possibly related toincubation we should not overlook the group known as cognitivestyles. In my reviewsof these traits (Guilford, 1979, 1980), at leasttwo kinds of cognitive styles were recognized. One type is in theform of intellectual controls or "intellectual executive functions,"and the others are intellectual preferences or interests. In eithercase, the cognitive styles tend to be distinguished along the linesof sections of the Sttucture-of-lntellect model.

For example, there are preferences for dealing with classesversus relations versus systems, and for visual versus auditoryversus kinesthetic information, and for divergent productionversus convergent production. Probably the best-known trait ofthis nature is Witkin's Field-Independence versus Field­Dependence variable. My interpretation of this trait is that it is atendency to seek or to produce transformations. The evidencefrom scattered sources shows that Witkin's tests of Fl-FD correlatepositively and significantly with tests that also measure transfer­mation abilities. They may be tests involving visual, semantic, orbehavioral information, and the operations of cognition, divergentproduction, or convergent production. Further connectionsbetween other cognitive styles and incubation can possiblybe found.

7

RESEARCH ONINCUBATION

TEACHING FORINCUBATION

REFERENCES

The Journal of Creative Behavior

There have been very few attempts to investigate the phenomenonof incubation by experimental methods. One obvious reason forthis is that control of what a"Subject does, other than his incubativeactivity, during the period of incubation is very difficult, except forvery short periods, lasting a matter of minutes. There have been afew experiments reported. One of them was conducted by Patrick(1938). She had one group of students work on planning a certainkind of research while in the laboratory and another group workedon a solution as homework. Fulgosi and Guilford (1968, 1973)had better control during incubation periods that lasted from avery few minutes up to-an hour, the interval being filled with workon other problems. More studies of the latter type could be done.

There are. a number of things that need to be determined withregard to incubation: the conditions under which it normally oc­curs; the conditions that favor its occurrence or that prevent it;and the conditions favorable or unfavorable for its success.Amongthese conditions are personality traits that are related to it posi­tively or negatively.

Features of incubation that we already know should be sugges­tive of problems to be investigated and hypotheses to be tested.If this information isnot regarded as sufficient, one could gain newinformation by resorting to interviews of creative people. preferablywith standardized questions based on what we already know, butleaving the way open for spontaneous suggestions orforfollowingup on leads that come out in the course of the interview. Anotherapproach would be group brainstorming sessions on what to donext in the way of research.

Enough seems to be known to justify attempts to teach problemsolvers how to employ incubation and how to do it successfully.Emphasis should be placed on avoiding premature closure. eitherby giving up or by settling for an inadequate solution, and theserious need for continued motivation. The key role of transforrna-

1

tions should also be emphasized, with practice in that kind ofactivity. The learner's personality traits might be assessed, andany signs of favorable or unfavorable dispositions might be dealtwith accordingly.. Imparting determining features to the learnershould be helpful. contributing to his improved self-management.

CHRISTENSEN, P. R., GUILFORD, J. P. s WILSON, R. C. Relations of creativeresponses to working, time and instructions. Journal of Experimental Psy·chology. 1957,53,82·88.

DAVIS, D. R. & SINHA, D. The effect of one experience on the recall of another.Quanerly Journal of Psychology. 1950,2, 43·52,(a).

DAVIS,D. R. & SINHA, D'The influence of interpolated experience on recognition.Quaneriy Journal of Psychology, 1950,2, 132·137,(b).

8

Some Incubated Thoughts on Incubation

FULGOSI, A. & GUILFORD. J. P. Short-term incubation in divergent production.Amefican Journal ofPsychology, 1968. 81, 241-246.

FULGOSI. A. & GUILFORD, J. P.A further investigationof short-termincubation.Acta insUtuti Psychologie Universitatis Zagrebiensis, 1973, No. 70, 67-70.

GUILFORD. J. P. Personelitp. NYC:McGraw·HiII, 1959.GUILFORD. J. P. Cognitive psychology with a frame of reference San Diego:

EdITS, 1979.GUILFORD, J. P. Cognitive styles: whatare"they? Educational and Psychological

Measurement, 1980,40 (in press).HEIDBREDER, E An experimental study of thinking. Archives of Psychology,

New York, 1924. No. 73. 213-223.PARNES, S. J. Effects of extended effort in creative problem solving. Journal

of Educational Psychology, 1961,52,117'122.PATRICK, C. Scientific thought, Journal ofPsychology, 1938, 55-83.

SPEARMAN, C. Abilities of man. NYC: Macmillan, 1927.WALLAS,G. The art of thought. London: Watts, 19~.

WEINER, S. Effects of m6tivation on the availability and retrieval of memorytraces.Psychological Bulletin, 1966~ 65, 24-37.

WOODWORTH, R. S. Experimental Psychology. NYC: Holt, 1938.

J. P.Guilford, Emeritus ProfessorofPsychology, Universityof Southern California.Address: Box 1288, Beverly Hills, California 90213.