European Journal of Social Psychology, Vol. 20,519-523 (1990)

Short Note

The effects of ingroup and outgroup homogeneity on ingroup favouritism,

stereotyping and overestimation of relative ingroup size

BERND SIMON Universitat Munster, Federal Republic of Germany

PAWEL MLlCKl Universiteit te Utrecht, The Netherlands

LUCY JOHNSTON University of Bristol, U. K.

ANTONIO CAETANO lnstituto Superior de Ciencisa do Trabalho e da Empresa, Lisboa, Portugal

MIROSLAW WAROWlCKl Wyzsza Szkoia Nauczycieiska, Oisztyn, P oiand

AD VAN KNIPPENBERG Universiteit te Nijmegen, The Netherlands and RICHARD DERIDDER Universiteit te Tilburg, The Netherlands

Abstract

An experiment (n = 61) investigated the efects of ingroup and outgroup homogeneity on ingroup favouritism, stereotyping and the overestimation of relative ingroup size. As predicted, outgroup homogeneity was conducive to ingroup favouritism. Ingroup homogeneity, however, failed to influence ingroup favouritism. Also unexpectedly, asym- metry in group homogeneity - irrespective of whether the ingroup or the outgroup was the more homogeneous group - led to pronounced stereotyping of both groups and to the overestimation of relative ingroup size.

INTRODUCTION

The present study investigates the effects of perceived intragroup similarity or homo- geneity on three intergroup phenomena, namely ingroup favouritism, stereotyping This research was conducted during the summer school of the European Association of Experimental Social Psychology, Tilburg, The Netherlands, August, 1989. The authors would like to express their thanks to John Rijsman, dean of the summer school, and his coworkers for their friendly and competent support during that time.

Requests for reprints should be sent to the first author.

0046-2772/90/0605 19-05$05.00 0 1990 by John Wiley & Sons, Ltd.

Received 27 December 1990 Accepted 20 April I990

520 B. Simon et al.

and overestimation of relative ingroup size. First, prior research indicates that per- ceived outgroup homogeneity, relative to heterogeneity, fosters the deindividuation of outgroup members and thus the tendency to favour the ingroup over the outgroup (Wilder, 1986; Miller and Brewer, 1986). On the other hand, perceived ingroup homo- geneity should foster the deindividuation or depersonalization of the ingroup thus strengthening social identification with the ingroup (Brown and Turner, 1981). Conse- quently, following social identity theory (Tajfel and Turner, 1986), which states that social identification leads to ingroup favouritism in order to achieve or maintain a positive social identity, we also expect ingroup homogeneity, relative to heteroge- neity, to increase ingroup favouritism.

Second, we assume that apparently homogeneous, and thus depersonalized, groups are likely targets of stereotyping (see Quattrone, 1986). Consequently, we hypothesize that a homogeneous idoutgroup is more readily ascribed stereotypical characteristics than a heterogenous idoutgroup.

Third, in line with research on the false consensus effect (Ross, Greene and House, 1977), group members can be expected to overestimate ingroup relative to outgroup size (Simon and Mummendey, 1990). Additionally, people might assume homogeneity to be a characteristic of small rather than large groups. Thus, outgroup homogeneity might further augment the overestimation of relative ingroup size while ingroup homogeneity might reduce it.

In sum, we make the following predictions: (1) Both ingroup and outgroup homo- geneity will increase ingroup favouritism. (2) Ingroup homogeneity will increase stereotyping of the ingroup and outgroup homogeneity will increase stereotyping of the outgroup. (3) While ingroup homogeneity will lessen the overestimation of relative ingroup size, outgroup homogeneity will increase it.

METHOD

Subjects, procedure and factorial design

Sixty-one female and male students from Tilburg University - mean age 20.6 years - participated on a voluntary basis. The study was introduced as being concerned with the relationship between artistic preferences and behaviour in social situations. Then, subjects were categorized into two groups (group A and group B). Categoriza- tion was allegedly based on subjects’ preferences for paintings by two different painters (painter A and painter B); in fact, however, it was purely random. Before subjects were informed about their group membership, the degree (high versus low) of homogeneity of the two groups had been manipulated orthogonally. Subjects were told that usually members of the respective group do (not) ‘display very similar attitudes, opinions and behaviours to one another in various social situations’. Sub- jects were run in four independent sessions, one session for each combination of the two between-subjects factors, homogeneity of group A (high versus low) and homogeneity of group B (high versus low).

Dependent measures

On seven-point scales (1 = not similar at all, 7 = very similar), subjects first rated the degree of similarity within group A and within group B. They then estimated

Efects of ingroup and outgroup homogeneity 521

how much they thought that group A members and group B members would like two additional paintings' (actually displayed on the screen) - one identified as by painter A, another as by painter B. For each subject, we later subtracted the assumed ingroup liking for the outgroup painting from the assumed ingroup liking for the ingroup painting. And the assumed outgroup liking for the ingroup painting was subtracted from the assumed outgroup liking for the outgroup painting. Thus, these difference scores reflect the extent to which each group is seen as preferring the painting of its own group to the painting of the other group. In other words, these scores can be interpreted as indices of the extent to which ingroup or outgroup are stereotyped (i.e. are seen as having stereotypical preferences). Furthermore, sub- jects were told to imagine a government grant (1 80 000 Dutch guilders) being available to support exhibitions by the two painters. On a matrix, subjects were to indicate a preference for the split of the money. The allocation matrix contained seven choices, ranging from /180000 and 0 guilders/ to /O and 180000 guilders/ for painter A and painter B respectively. Finally, before they were debriefed, subjects estimated the percentage of group A and group B members both in the experimental session and in the Dutch population as a whole.

RESULTS AND DISCUSSION

Manipulation check

The manipulation of ingroup and outgroup homogeneity was successful. Perceived similarity within ingroup was higher in the high than in the low ingroup homogeneity condition (M(H1GH-IN) = 5.7, M(L0W-IN) = 3.0; F(1,54) = 39.47,~ < 0.0005). Per- ceived similarity within outgroup was higher in the high than in the low outgroup homogeneity condition (M(H1GH-OUT) = 5.8, M(L0W-OUT) = 3.2; F(1,54) = 48.87,~ < 0.0005; see also Table 1).

Ingroup favouritism

Subjects' money allocations were scored from 1 to 7 according to the degree to which they favoured the ingroup painter relative to the outgroup painter. As pre- dicted, outgroup homogeneity was conducive to ingroup favouritism. Given high outgroup homogeneity, the ingroup painter was favoured, while no such ingroup favouritism was observed when the outgroup was heterogeneous (M(H1GH-OUT) = 4.4 M(L0W-OUT) = 3.7, F( 135) = 6 . 1 0 , ~ < 0.05; only the first mean differs signifi- cantly from the fairness point 4, p < 0.05). But contrary to our hypothesis, ingroup homogeneity did not increase ingroup favouritism. Rather, there was a nonsignificant

' trend in the opposite direction. (M(H1GH-IN) = 3.9, M(L0W-IN) = 4.2, F( 135) = 2.48, ns).

' Although both paintings had been rated equally likeable in a pretest, data from the main study indicated that subjects in general preferred the painting by painter A to the painting by painter B. The findings reported in this paper were not affected by this differential liking in a way relevant to our hypotheses. A more detailed report is available from the first author on request.

522 B. Simon et al.

Table 1 . Perceived homogeneity (Homo) and size (Size) of ingroup and outgroup and stereo- typing (Ster) of both groups

Ingroup homogeneity High Low

Ingroup Outgroup Ingroup Outgroup * *

Homo 5.2 5.1 2.4 6.5 High Size 50.8 49.2 60.5 39.5

Outgroup Ster 0.13 1.73t homoge- neity Homo 6.2 * 2.5 3.6 3.8

Low Size 60.4 * 39.6 54.4 45.6

Ster 1.08t -0.15 Due to missing data cell numbers vary from 13 to 17. * Means for ingroup and outgroup (per cell and per measure) differ at the 0.05 level of significance or better (1-test, two-tailed). t Ster-mean is significantly different from zero at the 0.05 level of significance or better (t-test, two-tailed).

Stereotyping

The ingroup-outgroup variable was included in the ANOVA design as a within- subjects factor, but had no influence (no significant main or interaction effect). Unexpectedly, however, the two-way interaction between ingroup homogeneity and outgroup homogeneity was significant (F(1,56) = 12 .58 ,~ I 0.001). Given asymmetry in homogeneity, both ingroup and outgroup were seen in stereotypical terms, while there was virtually no stereotypical perception when both groups had the same degree of homogeneity (see Table 1).

Overestimation of relative ingroup size

The size estimates referring to the particular experimental session and those to the Dutch population in general were averaged (correlation between these estimates: +0.69, p < 0.0005). Although overall the ingroup was seen as the majority and the outgroup as the minority (M(1G) = 56.3, M(0G) = 43.7, F(1,56) = 13 .69 ,~ < 0.0005), this effect was qualified by a three-way interaction between ingroup homogeneity, outgroup homogeneity and the ingroupoutgroup variable (F( 1,56) = 4 . 9 0 , ~ < 0.05). The ingroup was seen in the majority position vis-d-vis the outgroup only in the asymmetry cells, i.e. when one group was more homogeneous than the other, irrespec- tive of whether the ingroup or the outgroup was more homogeneous (see Table 1).

In sum, the results presented here lend further support to Wilder’s (1986) assump- tion that perceived outgroup homogeneity is an important antecedent of intergroup discrimination. We also examined the influence of perceived ingroup homogeneity, but failed to obtain any substantial effect on ingroup favouritism. Finally, our specific expectations regarding the effects of perceived group homogeneity on stereotyping and overestimation of relative ingroup size were disappointed. Yet interestingly, parallel effects were found in both cases. An asymmetry in perceived ingroup and outgroup homogeneity led to stereotypical perception of both groups and an over- estimation of relative ingroup size. We have no conclusive explanation for these

Eflects of ingroup and outgroup homogeneity 523

novel effects, though one might speculate that the asymmetry in homogeneity contri- buted to the salience of the intergroup situation thus facilitating stereotyping and overestimation of relative ingroup size. In any case, these novel effects deserve more attention in future research.

REFERENCES

Brown, R. J. and Turner, J. C. (1981). ‘Interpersonal and intergroup behaviour’. In: Turner, J. C. and Giles, H. (Eds) Intergroup Behaviour, Basil Blackwell, Oxford.

Miller, N. and Brewer, M. B. (1986). ‘Categorization effects on ingroup and outgroup percep- tion’. In: Dovido, J. F. and Gaertner, S . L. (Eds) Prejudice, Discrimination and Racism, Academic Press, London, pp. 209-230.

Quattrone, G. A. (1986). ‘On the perception of a group’s variability’. In: Worchel, S. and Austin, W. G. (Eds) Psychology oflntergroup Relations, Nelson-Hall Publishers, Chicago.

Ross, L., Green, D. and House, P. (1977). ‘The false consensus effect: An egocentric bias in social perception and attribution processes’, Journal of experimental Social Psychology,

Simon, B, and Mummendey, A. (1990). ‘Perceptions of relative group size and group homo- geneity: We are the majority and they are all the same’, European Journal of Social Psy-

Tajfel, H. and Turner, C. J. (1986). ‘The social identity theory of intergroup behavior’. In: Worchel, S. and Austin, W. G. (Eds) Psychology of Intergroup Relations, Nelson-Hall Pub- lishers, Chicago.

Wilder, D. A. (1986). ‘Social comparison: Implications for creation and reduction of intergroup bias’. In: Berkowitz, L. (Ed.) Advances in Experimental Social Psychology, Vol. 19, Academic Press, New York, pp. 291-355.

13: 279-301.

chology, 20: 351-356.