The role of assimilation and differentiation needs in the perception and categorization of ingroup and outgroup members

According to optimal distinctiveness theory (ODT; Brewer, 1991, 1993), individuals have both the desire for assimilation (inclusion within a group) and also the desire for differentiation (distinctiveness from others). In order to reconcile these two competing needs, optimal distinctiveness theory states that individuals will seek social identities that are at the equilibrium point between the two needs. In other words, individuals will identify with groups that allow for both assimilation and differentiation. Although the needs for assimilation and differentiation can lead to differences in the groups with which individuals identify, these needs may also have an effect on the process o f categorizing others as ingroup and outgroup members. According to ODT, the inclusiveness of a particular group membership is inversely related to the amount of differentiation the group provides and directly related to the amount o f assimilation provided by the group. Thus, one way in which individuals may attempt to satisfy their assimilation and differentiation needs is by being either more restrictive or more lenient in terms o f defining who belongs to the ingroup and outgroup. Three studies were conducted in order to explore the role o f assimilation and differentiation needs in the process o f social categorization. Recent research on the ingroup overexclusion effect—the tendency to be stringent in one’s criteria for ingroup membership—and an older body o f literature on ethnic identification indicates that social categorization may be influenced by the goals and motivations that perceivers possess. Although research on the ingroup overexclusion effect and research on racial categorizations suggest that individuals have a general default towards stringency when categorizing others as ingroup members, a different set of predictions was derived from Brewer’s (1991) optimal distinctiveness model. It was predicted in the studies presented here that activating the needs for assimilation and differentiation would result in a relaxation or tightening of group boundaries leading to greater inclusion or exclusion of group members. More specifically, when the need for assimilation was aroused, participants were expected to be more lenient in their criteria for group membership, and when the need for differentiation was aroused, participants were expected to be more stringent. In addition, perceptions o f ingroup and outgroup homogeneity were predicted to be affected by assimilation and differentiation needs sych that greater perceived homogeneity would occur when participants’ need for differentiation was aroused. Contrary to predictions, both the arousal o f the need for assimilation and the arousal o f the need for differentiation led to greater stringency in defining group membership compared to control participants. In addition, perceptions of ingroup homogeneity increased when either the need for assimilation or differentiation was aroused. The results presented in this dissertation suggest that a bounded and homogeneous ingroup may be important for the satisfaction o f both assimilation and differentiation