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PergamonPcr.wn. mdiGd. Drfi Vol. 19. No. I. pp. 73-80. 1995

Copyrig ht 0 1995 Elaewer Science LtdPrinted in Grear Britam. All nghrs reserved0191~8869(95)00009-7 0 9 I -8869i95 59.50 + 0.00

PERSONALITY DIFFERENCES AND GROUP VERSUSINDIVIDUAL BRAINSTORMING

Adrian Fumham* and Tanya YazdanpanahiDepartment of Psychology, University College London, 26 Bedford Way, London WC I OAP, England

(Received I August 1994)Summary-This study examined the effects of personality (psychoticism) and nominal vs real groups usingbrainstorming techniques in problem solving. Subjects either brainstormed three problems on their own,in pairs or in four person groups consisting of similar personality scores. There were six dependent measures:total number of non-redundant ideas; number of superior responses; a rating on the quality of the ideas;the percentage of superior responses; a creativity production rate and a self-rating of imaginativeness. It waspredicted that high P scorers brainstorming alone would have the highest creative scores but when theyinteract with similar types of individuals in group settings, their superior score rate would be overtaken byequivalent groups of low creative individuals. This prediction was supported for four person groups on thenumber and percentage of superior response measures and the mean creative rate measure. Dyads totalcreativity scores were always lower than four person nominal or real groups or two individuals workingalone. There were almost no significant interactions between personality type, group size or the tasks used.Implications for organizations is discussed and the direction of future research is examined.

INTRODUCTIONBrainstorming was first claimed to be an effective method of group problem solving by Osbom (19.57),who argued that this technique increases the quality and quantity of ideas generated by group members.Since this claim was made, researchers have been investigating the technique and the factorsinfluencing it (Dennis & Valacich, 1993; Kameda & Sugimori, 1993).Osbom stated that by engaging in brainstorming the average person can think up twice as manyideas when working with a group than when working alone (Diehl & Stroebe, 1987). Taylor, Berryand Block (1958) were the first to reject the claim. They found that nominal groups (which are madeup of Ss who brainstorm alone and then had their non-redundant ideas combined) out-performedinteracting groups of the same number. This finding has been consistently replicated and the researchhas significantly advanced during the last three decades. The most influential initial work was carriedout in the 1970s by Bouchard and his colleagues, where they manipulated among other things the groupsize and Ss sex and even modified the brainstorming procedure itself, in order to understand what infact determined the problem-solving effectiveness of groups and individuals (Bouchard, 1969, 1972;Bouchard & Hare, 1970; Bouchard, Drauden & Bersaleux, 1974). The work conducted during the1980s and 1990s tried to answer the question as to why individuals performed better than groups(Paulus & Dzindolet, 1993; Paulus, Dzindolet, Poletes & Camacho, 1993). Throughout the past fewyears the theories and models proposed were used along with advanced computer technology todevelop electronic brainstorming systems. The most recent research illustrates their effectiveness inovercoming problems such as criticism, production blocking, social loafing and evaluationapprehension (Gallupe, Bastianutti & Cooper, 1991; Gallupe, Cooper, Grise & Bastianutti, 1994).

Brainstorming experiments usually involve unstructured, open-ended, creative tasks. The taskstraditionally used ranged from the Thumbs problem (whereby the benefits and difficulties of growingan extra thumb on each hand were assessed) to the Blind World problem (which involved thinkingup the consequences if suddenly everybody went blind). The methodological diversity of theseexperiments makes it very hard to compare one study with another. Attempts have been made to finda universal index of performance (Thomberg, 1991) called the creative production per cent (CPP),(group + individual output X 100). The majority of studies have made use of four person groups butstudies investigating dyads as well as much larger groups do exist. We reviewed the results of thefour-person groups conducted from 1958 to 198 1. They have a CPP range of 25-l 25. Although the*To whom reprint requests should be addressed.

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74 Adrian Fumham and Tanya Yazdanpanahimajority lie around 60-70 CPP, the extreme values could be accounted for by methodologicaldifferences, such as variations in the task requirements, differences in quality measurements (forexample, some studies assess quality as the average quality but others rate total quality and differencesin time allowance and brainstorming instructions).

In 1970 Bouchard and Hare investigated group size and compared groups of five, seven and ninecompared to the equivalent nominal groups. The previous experiments had never gone abovefour-person groups, yet Osbom had suggested that optimal brainstorming groups was between fiveand 10. Their prediction that the growth curve of nominal groups would level off and be overtakenby that of the real groups was not confirmed. Instead they found that there was a nominal group effectup to groups of nine-persons.

Considerable research has been directed at answering the question: why are real groups repeatedlyless productive than the same number of individuals working alone? Diehl and Stroebe (1987)identified three potential group effects; social loafing, evaluation apprehension and productionblocking. Working in groups has traditionally been seen to have potentially two opposing effects; thatof social loafing and that of social facilitation. Social loafing is described as the finding that interactinggroup members (with pooled outputs) will exert less effort than similar participants working alone(Harkins, 1987). Depending on the task however, findings from social facilitation studies have shownthat group participants performance which are individually identifiable will be greater than the outputfrom Ss working alone on tasks. In order to explain the latter phenomenon, investigators have urgedalong the lines of a preference theory and an evaluation theory. The former theory argues that themere presence of others leads to an increased motivation to perform and the latter theory argues thatthe presence of others becomes associated with evaluation and/or competition among other things,which again will increase the motivation to perform. Social loafing studies have tended to identifya group vs individual effect rather than an evaluation effect.

Williams, Haskin and Latare (198 1) demonstrated that identifiability of individual output was animportant factor involved in evaluation. Harkins and Jackson (1985) tested this notion using abrainstorming technique and found that identifiability was a factor involved in evaluation but onlywhen this output evaluation took place as a result of competition with co-workers.Kerr and Bruun (1983) claimed that social loafing depended heavily on task features: whether thetask was disjunctive (where only the best answers counted) or additive (where outputs were summed).They claimed that dispensability (and hence the likelihood to loaf) matters less with additive tasksthan disjunctive tasks. The possibility of redundancy may in fact promote dispensability. Social loafingcould be deemed responsible for only a small proportion of productivity loss and other processes mustbe contributing. This may be a consequence of the nature of brainstorming, which requires little effort,as opposed to physical tasks where loafing may account for more loss (Diehl & Stroebe, 1987).

A second possible interpretation which has been offered to account for low real group productivityis evaluation apprehension. Many individuals refrain from expressing their views in various socialsettings such as the classroom or the boardroom because they are uncertain as to how they are goingto be received. This notion of fear of negative evaluation from other group members has beeninvestigated as a plausible cause of productivity loss in brainstormin g groups; but the results have beensomewhat contradictory. Colaros and Anderson (1969) concluded that productivity was lowest in thecondition which aimed to produce the highest amount of evaluation apprehension. This findingdiffered from Maginn and Harris (1980) who found that: individual productivity in the presence ofobservers was not significantly different from that of individual subjects working without observers.However, the methodology of the two experiments was dissimilar in that the former experimentinduced evaluation apprehension by deceiving the Ss with respect to the number of experts that werepresent in the group, but the latter experiment manipulated evaluation apprehension by telling Ss thatthree external judges were observing them. Furthermore, this latter experiment investigated onlyindividuals working alone and aimed to lower productivity (to that of real groups) with apprehension,but the former experiment dealt with real groups and aimed to illustrate an increase in productivityin the no-expert condition. The lack of support found in this area indicates that a more powerful causeof productivity loss exists.

Production blocking is the notion that due to the fact that only one individual can speak at a giventime in a group, other group members are prohibited from airing their ideas when you occur to them.This waiting time can cause them to forget (due to the limitation of the short term memory) or consider

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Group vs individual brainstorming 75the idea to be less original or relevant with respect to the presently viewed idea. This opposes theoriginal claim that brainstorming allows individuals to verbalize their ideas which in turn wouldstimulate other members.. Traditionally brainstorming has adopted equal man-hour methodology.Members of real groups of size n, have only llnth of the amount of speaking time of the equivalentnominal group members. By varyin,0 nominal group members time allowance, so that it wascomparable to real group members assumed time allowance, Diehl and Stroebe (1987) tested whetherthis procedural explanation of the blocking effect was valid. Two experiments manipulating timeallowance or even speaking time allowance showed that it failed to produce a reduction in theproductivity gap between real and nominal groups.New computer aided techniques to unblock brainstorms have only recently been constructed andtested (Gallupeetaf., 1991; Gallupe, Dennis, Cooper, Valacich, Bastianutti & Nunamaker, 1992). Thisnew technique is called electronic brainstorming and aims to overcome the problems of socialloafing, evaluation apprehension and production blocking. Electronic brainstorming involves groupmembers sitting at computer terminals and typing in their ideas but also having full access to the othersideas as they are produced. It aims to intergrate the two important and advantageous features ofnominal and real group brainstormin g, namely being able to freely generate ideas and also being ableto share respectively. Ideas on the screen have not been found to be distracting which was the casewith traditional brainstorming (Gallupe et nl., 1991). Simultaneous contributions lessen the potentialeffect of blocking and the anonymous nature of the technique alleviates evaluation apprehension. InGallupes original and pioneering study comparing electronic and non-electronic brainstorming, hefound that electronic brainstorming four-persons groups outperformed the four-person traditional(verbal) brainstorming groups and failed to find a difference between nominal and interacting groupsusing the electronic technique. In electronic brainstorming groups, performance increased with groupsize, which contrasts with non-electronic brainstorming groups, which failed to increase with groupsize growth. Electronic brainstorming was not advantageous when only two people were involved (andthus anonymity and production blocking was at its lowest) but as group size and therefore anonymityand production blocking increased, the true potential of this new technique was exhibited. Per-personproductivity and average per-person output of ideas tends to remain stable with an increase in groupsize (unlike non-electronic brainstorming where a fall was noted). This was attributed to the fact thatproduction blocking remained at a constant low level throughout different electronic brainstormingsessions. Lastly, satisfaction is greater with electronic brainstorming groups and this increases withgroup size, contrary to non-electronic brainstorming.

This study is concerned specifically with individual differences and group interaction inbrainstorming tasks. The brainstormin g literature appears to have neglected individual differenceswhich could be a major source of variation. More specifically, it is concerned whether creativethinkers (as measured by their psychoticism score) are superior in group or individual brainstormingtasks. Few studies in the area of brainstorming have considered individual differences, even the mostobvious possibility that trait-creativity might interact with individual vs group production of ideas.

Since the last century creativity has been linked with psychosis. Eysenck (1992) argued that as aresult of evidence identifying relatives or descendants or psychotics as highly creative, creativity isa function of psychoticism (P), which is a predispositional trait to the development of psychoticsymptoms (Eysenck & Eysenck, 1976). This concept is very similar to Bleulers schizoid personalitywhich was also regarded as predisposing to creativity (Bleuler, 1978) as well as being noticed priorto psychotic breakdowns (Claridge, 1985). Nevertheless, the two terms psychosis and psychoticism(of which the latter predisposes a person to the former) must not be confused and it is probably thelatter which is most closely linked to creativity (Rushton, 1990).

Five different sources of evidence have been presented which support the P-creativity link model:first, individuals genetically related to psychotics (and thus likely to be high on the psychoticism scale)have been shown to be highly creative. Heston (1966) found the offspring of schizophrenic mothers(and raised elsewhere) were highly artistic and imaginative compared to non-schizophrenics.Secondly, P has been correlated with tested creativity using creativity tests (Woody & Claridge, 1977).Third, P was found to be related to creative achievement of a higher order (Gotz & Gotz, 1979). Fourth,highly creative individuals exhibit greater psychopathology than less creative individuals (Eysenck,1992) and this appears greater than chance would predict. Fifth different cognitive styles have beenregarded to be characteristic of psychotics, high P-scorers and creative achievers (Eysenck, 1992).

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76 Adrian Fumham and Tanya YazdanpanahiThree hypotheses were proposed suggesting that there will be a main effect for group size (given

the fairly consistent brainstorming literature): personality (given the recent P-score literature) andmore importantly an interaction between personality and group size. It was hypothesized:(1) That nominal brainstorming groups will outperform real interacting groups of two or four

individuals. (That is, nominal groups of individuals perform better than interacting groups.)(2) That high P scorers will have higher scores on a creativity test than low P scorers. (That is, therewill be a main effect of personality.)

(3) That (high P scorers) brainstorming alone will have the highest rate of creative achievement butwhen placed in interacting groups consisting of similar highly scoring individuals (on thepsychoticism scale), this rate is overtaken by low P scorers working alone. (That is the benefitof trait-creativity is washed out in groups because of production blocking.)

METHODSubjectsFifty-two psychology first year undergraduates took part in the experiment. The ratio ofmales:females was 3:7 but two-thirds of the male Ss fell into the high P group. Sex and P are thusconfounded and as a result every effort was made to keep the sex distribution in groups consistent.The age range was approximately between 18 and 50 yr old but most were between 19 and 24 yr old(mean 22.3; SD = 7.1).

Independent variableCreativity rype. High or low creativity was predetermined on the basis of the Ss P-score on the

EPQ (Eysenck & Eysenck, 1975). The P-score ranged from 0 to 16 but only two Ss in the samplescored above nine. Ss who scored above four were placed in the high group and those who scoredfour or less, were put in the low group. The modal score for this population is in fact four.

Dependent variableS s were required to complete three tasks; the first took 5 min and required the Ss to suggest as many

different (good trade) names for a new chocolate bar. They were given the description of a new typeof chocolate bar about to go onto the market and asked to think up a good name for it. The secondtask, which took 10 min, involved studying a cartoon sketch and writing down as many ideas as towhat may occur next. This was a typical picture from a cartoon series but incomplete with a full setof pictures which could make up the final joke. Ss were required to think up and very briefly describealternative endings/next steps in the story. The third task which lasted 15 min, involved thinking upa complete television advert about a new cough medicine on the market. The medicine was describedalong with particular advantages and disadvantages. This task was like the first but more complicatedin that it involved thinking through the full story-board of pictures and text for the advertisementbut not necessarily the product name. Ss were told that both the quality and quantity of their ideascounted and that they should produce as many as possible in the time allocated. From these tasks itwas possible to derive six different dependent variables:(1) The total number of non-redundant (i.e. non-overlapping) ideas.(2) The mean creativity score measured on a scale of l-5 by trained raters consisting of students

who had studied the creativity literature (Cooper, 1991).(3) The number of superior responses. A superior response was an idea which scored -C r 5 on the

above creativity rating.(4) The percentage of superior responses out of the total number of non-redundant ideas.(5) The creative production rate. This was the total number of ideas which were thought up for each

task, divided by the number of individuals working on the task.(6) Self rating of imaginative ability on a scale of 1 (low) to 10 (high).

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Group vs individual brainstorming 77Table I. Meanumber o f non-redundant and superio r ideas produced by the various group\

Total ,V = 52Glenn number, of

non-redundant ideas Supenor idea

(A) High Psychoticism Real group (four-persons) 49.33(B) High Psychoticism Nominal group (four-persons) 133.00(0 High Psychoticism Real group (two-persons) 52.00CD) High Psychoticism Nominal group (two-persons) 66.50(E) Low Psychoricism Real group (four-persons) 15.so(F) Low Psychoticism Nominal group (four-persons) 133.00(G) Low Psychoticism Real group (two-persons) 3 I .oo(H) Low Psychoticlsm Nominal group (two-persons) 46.50

*There were two set s of each of the groups specified but three proups in the G and H.

10.7544.00IO.8022 00I-t.2521.00

2.67I OS0

Scoring and analysisQuantity. The non-redundant ideas were counted, but when two identical ideas were contributed

in the nominal groups, they only counted as one idea. The different ideas could easily be identified.In task I, a name constituted an idea-e.g. Zebra bar. In task II, each small part of the storyconstituted an idea-e.g. the charmer charmed the man in order to run off with the woman. Thiswas counted as one idea. In task III, the Ss described an advert through a number of points. such asthe opening scene, the slogan, the name of the medicine and so forth, and each of these points wascounted as an idea. This was checked by a second person to ensure reliability.

Qua/iv. The quality was rated according to originality on a five point scale [ 1 (low)-5 (high)], byone experimenter. In order to test score reliability, a second experimenter also rated 2.5% of the totalideas. The results showed that the raters agreed on 92.17% on the scores and the remainder werenegotiated till a 100% agreement was obtained.

ProcedureIn all 80 Ss completed the EPQ and from this number a subset were contacted based on their P scores.Once the Ss had been allocated to their creativity group type (either high or low based on their P scores)

and were randomly put in a group type, they were given a booklet which contained a set of standardbrainstorming instructions (Bouchard & Hare, 1970). The booklet also contained the instructionsconcerning the nature of the tasks and the tasks themselves. In the group conditions, one member wasnominated to write down the ideas thought up by the group was remind that each persons contributionwould be evaluated by means of a tape-recorder. The groups worked in small cubicles and used blankwhite paper provided to record their ideas. The experimenter started the group off on the first taskand timed them with a stop-watch for 5 min. This was repeated for the second and third task for timingsof 10 and 15 min, respectively. The tape recorder was switched on at the start of the session and turnedoff only at the end of the experiment. The main purposes of the tape-recorder was to firstly. makethe Ss feel that their contributions were counting and secondly, to provide a back-up in case Ss didnot write their answers down. The second reason was to induce some evaluation apprehension andminimise social loafing. The individual sessions were not tape-recorded.

RESULTS

To get some idea of the results over all the three different tasks, data was pooled. Table 1 showsthe unit of analysis (dependent variable) which was the total mean number of non-redundanr ideasand the number ofsuperior ideas for both real groups (four-person and two-person) and nominalgroups (four-person and two-person groups). The t-tests were carried out between (i) high P-scoringreal and nominal four-person groups superior ideas (t = 6.40; P < 0.005) and number of ideas(t = 6.65; P < 0.05); (ii) high P-scoring real and nominal two-person groups superior ideas (t = 2.8 I ;P < 0.05) and number of ideas (t = 1 Ol; ns); (iii) low P-scoring real and nominal four-person groupssuperior ideas (t = 0.94; ns) and number of ideas (t = 10.55; P < 0.001); (iv) low P-scoring real andnominal two-person groups (t = 1.35; ns) and number of ideas (t = 1.80; ns); (v) generally real andnominal four-person groups (t = 3.27; P < 0.001) and number of ideas (t = 13.68; P < 0.001): (vi)

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78 Adrian Furnham and Tanya Yzzdanpanahigenerally real and nominal two-person groups (f = 1.92; P < 0.05) and number of ideas (f = 1.90:P < 0.05).

The r-tests showed that on the measurement of total number (as opposed to superiority) ofnon-redundant ideas, in either high or low P conditions, the two-person nominal groups did no betterthan the real interacting pairs. When the data was collapsed across P groups this comparison betweeninteracting and nominal pairs, only just becomes significant. With the four-person comparison,interacting groups produced significantly fewer ideas than their equivalent nominal group. This wastrue for both high and low P groups.

However, this preliminary analysis obscures the task differences which may have led to quitedifferent patterns of findings. The scores for the six different measures testing the performance ofindividuals working alone, interacting pairs and interacting groups of four persons, were thensubjected to a 2 X 3 X 3 mixed ANOVA (two personality groups; three working conditions; threetasks) with high/low psychoticism scores groups and working conditions (interacting groups of four,two and working alone) being between group measures and tasks being a within variable.

The first measure, ro&zlnumber of ideas, showed only a main effect of task. The first task producedmore ideas than the second and third, respectively [F (250) = 8.20, P O.OOl]. However, there wereno other main effects or interactions. Superior responses (which are related to the quality of answersproduced), showed three main effects: that of P score type , group and task. High P scorers produceda greater number of superior answers (F= 6.94, P

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Group vs individual brainstorming 79the Creative Production Percent an increase with group size ceased at two-person groups (Bouchard& Hare, 1970). This and other results (Torrance, 1974) led to speculation that dyads were in fact aspecial group. In the present study, the nominal two-person groups can be observed to produce morenon-redundant ideas and more superior ideas than the real groups but apart from the significant highP score group, they just fail to be statistically significant.

The second hypothesis predicted that P scorers would generally have a high creative qualityanswers. Despite the fact that the study contained a relatively small number Ss and that only two ofthe Ss scored above nine on the EPQ P-scale the hypotheses were confirmed. The results of this analysistherefore support Eysencks theory of a relationship between personality (psychoticism) andcreativity. On a number of the measures, such as superiority of responses, percentage of superiorresponses and mean creativity rate, a main effect of creativity type (P) was found. Therefore, withthe limitations suggested above, those that were classed as having high P-scores (high creativity/orig-inality traits) tended to produce a higher level of creative responses. Their ideas were constantly ofa high quality and there was a larger percentage of them compared to those individuals categorizedas having low creative abilities.

The third hypothesis was that in high P scoring Ss brainstorming alone would produce the highestrate of non-redundant and superior responses, but when these individuals are placed in interactinggroups consisting of similar high scores this superior rate would be overtaken by low P scoring groups.Highly creative people have been claimed to be self-assertive, non-conformists and independent(Barron, 1972). It is for this reason, among others, that they may not be able to share, build and workon others ideas, which will push the group productivity down even more. Creativity x groupinteractions approached, but were strictly not significant.

The interaction found with the self-rating measure was slightly different to the above threesignificant findings. When individuals are alone, low P scorers rate themselves as having a fairly highlevel of imaginative ability (mean = 6.50) whereas those individuals who scored highly on the P scalevisualise themselves as having rather poor imaginative abilities (mean = 4.82) when they are on theirown. This however changes and tends to be in line with the classification scheme, when similarlygrouped individuals get together as interacting two- or four-person groups. Thus, high P socrers ratethemselves accordingly (pairs = 7.00 and four-person = 6.70) as do low P scorers (pairs = 5.50 andfour-person = 5.72). It is possible that when individuals are placed in a group with their own type,their initial either over- or under-estimations adjust accordingly, as they have people to comparethemselves to and form a more realistic view.

Main effects for group type were found for superior responses, mean creativity rate and percentageof superior responses which are all quality measures. Thus, regardless of whether high P scorers werebetter or worse than their equivalent low scorer types, the four-persons group productivity was higherthan individuals. This is to be expected, as a group of four people will inevitably produce more ideasas a whole and this, as previously mentioned, is a contributing factor causing people to believe thatthey will achieve more in a group! The creative production rate however confirms that this measureper person decreases as group size increases. The interesting characteristics in this finding, is that forthe quality measures, the trend from individual alone to four-person groups always dips with theinteracting dyads. This was confirmed by post hoc Scheffe tests. Thus, an individual alone seems tohave a higher mean creativity rate, a greater number and percentage of superior responses than twointeracting individuals (regardless of creativity type) and four person groups have the overall highestquality even though creative production per person is lowest for the latter group. What causes thisdyad dip is however not clear.The direction of further research in this area may utilize electronic brainstorming technology. Theinvestigations into this technique have shown it to be promising with respect to an increasing groupsize. Interestingly enough, the findings using electronic brainstorming methods have found that therewas no difference between traditional brainstorming techniques and electronic brainstorming forinteracting dyads (Gallupe er al., 1992). Due to the failure to find a four-person real vs nominalelectronic brainstorming difference (Gallupe et al., 199 l), the focus of attention can be on either typeof group. More specifically, what particular combination of individuals (that is, the ratio of males tofemales and the ratio of high to low P scorers) making up the group and of what size, produces theoptimal condition is unclear. An example of a potentially successful group, is perhaps one or two highP scorers constituting the power source of creative ideas, and the rest of the group made up of low

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80 Adrian Furnham and Tanya Yazdanpanahior middling P scorers who may be better at working on and combining these ideas and who are betterat appreciating responses made by their co-workers. The need for identifying different combinationsof groups is perhaps more relevant to traditional brainstorming methods because as a result of thenature of electronic methods, the above problems may not even arise. Nevertheless these resultssuggest that P scores do have an impact on the quality and quantity of ideas produced in traditionalbrainstorming tasks.

REFERENCESBarron, F. (1972). Arrisrs in the making. New York: Seminar Press.Bleuler, M. (1978). The schizophrenia disorders. New Haven: Yale University Press.Bouchard, T. J. (1969). Personality, problem-solving procedure and performance in small groups. Journal ofApplied

Psychology Monograph. 53, (I, Pt.2).Bouchard, T. J. (1972). A comparison of two group brainstorming procedures.Journal of Applied Psycholog.v, 59.4 1812 I.Bouchard, T. J. & Hare, M. (1970). Size, performance, and potential in brainstorming groups. JaurnalafApplied Ps.vchology.

54, 5 l-55.Bouchard, T. J., Drauden. G. & Barsaloux, J. (I 974). Brainstorming procedure, group size and sex as determinants of the

problem solving effectiveness of groups and individuals. Journal of Applied Psychology, 59, 135-l 38.Buyer, L. S. (I 988). Creative problem solving: A comparison of performance under different instructions. Journal of CreatiL,e

Behaviour. 22, 55-6 I.Claridge, G. (1985). Origins of mental illness. Oxford: Blackwell.Colaros, P. & Anderson, L. (1969). Effect of perceived expertness upon creativity of members of brainstorming groups.

Journal of Applied Psychology, 53, 1159-l63.Dennis, A. & Valacich, J. (1993). Computer brainstorms: More heads are better than one. Journal of Applied Ps.vcho1og.v.

78. 531-537.Diehl, M. & Stroebe, W. (1987). Productivity loss in brainstorming groups: Toward a solution of a riddle. Journal of

Personality and Social Psychology, 53, 497-509.Diehl, M. & Stroebe, W. (1991). Productivity loss in idea-generation groups: Tracking down the blocking effect. Journal

of Personaliv and Social Psychology, 61, 392-403.Eysenck, H. J. (1992). Creativity and personality: Suggestions for a theoF. Institute of Psychiatry. University of London

(unpublished).Eysenck, H. J. & Eysenck, S. B. Ci. (1975). The Evsenck personalitv quesrionnaire. London: Hodder & Stoughton.Eysenck, H. & Eysenck, S. B. C. (1976). Psvcho&m as a dimension of personaliry. London: Hodder 8: Stoughton.Gallupe, R. B., Bastianutti, L. &Cooper, W. H. (I 991). Unblocking brainstorms. Journal ofApplied Psychology, 76, 137-142.Gallupe, R. B., Dennis, A. R.. Cooper, W. H., Valacich, J. S.. Bastianutti, L. M. & Nuna Maker, J. F. (1992). Electronic

brainstorming and group size. Academy of Managemenr Journal, 35, 350-369.Gallupe, R. B., Cooper, W. H., Grise. M.-L. & Bastianutti. L. M. (1994). Blocking electronic brainstorms. Journal ofApplied

Psycho1og.v. 79, 77-86.Gotz, K. & Gotz, K. (1979). Personality characteristics of successful artists. Perceprual and Motor SkiUs, 49, 919-929.Harkins, S. G. (1987). Social loafing and social facilitation. Journal of Experimental Social Ps.vchologv, 23, I-18.Harkins. S. G. &Jackson, J. M. (1985).The role ofevaluation in eliminating social loafing. Personalif?andSocial Psycholog>

Bulletin, l/(4) 457465.Heston, L. (I 966). Psychatric disorders in foster-home reared children of schizophrenic mothers. British Journal of Ps.vchiatT,

112, 819-825.Kameda, T. & Sugimori. S. (1993). Psychological entrapment in group decision making: An assigned decision rule and a

group think phenomenon. Journal of Personality and Social Psycholog!. 65, 282-292.Kerr, N. & Bruun, S. (1983). Dispensability of members effort and group motivation losses: Free-rider effects. Journal ofPersonality and Social Psychology, 44, 78-94.

Maginn, B. K. & Harris, R. J. (1980). Effects of anticipated evaluation on individual brainstorming performance. Journalof Applied Psychology, 65, 2 19-225.Osbom, A. F. (1957). Applied imaginarion New York: Scribner.

Paulus, P. & Dzindolet, M. (1993). Social influence processes in group brainstorming. Journal of Personalit! and SocialPsychology, 64, 575-586.

Paulus, P., Dzindolet, M.. Poletes, G. & Camacho, L. (1993). Perception of performance in group brainstorming. Personalit>and Social Psychology Bullerin, 19. 79-89.

Rushton, J. P. (I 990). Creativity, Intelligence and Psychoticism. Personalig and individual D#ferences, / 1. I29 I- 1298.Stroebe, W.. Diehl, M. & Abakoumkin. (1991). The illusion ofgroup effectiviv. (p. 33) The Psychological Institute. University

of Tuebingen.Taylor, D. W., Berry, P. C. & Block, C. H. (1958). Does group participation when using brainstorming facilitate or inhibit

creative thinking? Administrat ive Science Quarterly, 3, 23-47.Thomberg, T. H. (I 99 I). Group size and member diversity influence on creative performance. Journal of Creative BehaLiour,25, 324-333.

Torrance, E. (1974). Torrance tests of creative thinking: Norms & technical manual. Lexington, MA: Gunn.Williams, K., Harkin, S. & Latane, B. (I 98 I). Identifiabil ity as a deterrent fo social loafing: Two cheering experiments. Journal

of Personality and Social Psychology, 40, 303-3 I I.Woody, E. & Claridge, G. (1977). Psychoticism and thinking. Brirish JournalofSocialand ClinicaL Ps.vcho/ogF, 16.241-258.