People report less variability within in-groups than within out-groups when they make their ratings on traits on which the in-group has a higher central tendency than the out-group. [Simon, 1992a] and [Simon, 1992b] proposed that this effect is motivated by the need to protect a positive social identity. The present research tested the necessity of the social identity motive by using participants who were not members of any of the target groups that they judged. In Study 1 (N = 60), psychology undergraduate students reported significantly less intragroup variability on positive traits among a group of fashion designers that won a fashion competition than among a group that lost. Study 2 (N = 75) found a reverse effect on negative traits and confirmed the mediating role of perceived central tendency. These results demonstrate that the social identity motive is not necessary to explain the effect of central tendency on ratings of intragroup variability, and that the effect is more general than previously reported.
Journal of Experimental Social Psychology Vol. 46, Issue 2, p. 410-415