Perceptions of group homogeneity during group formation and change

Research on the effects of categorization on intergroup perceptions has commonly reported the existence of an out-group homogeneity effect in which the out-group is seen as less internally heterogeneous than the in-group. An influential explanation for this effect is based on differential familiarity with in-group and out-group members. However, substantial evidence now exists for the reverse phenomenon-an in-group homogeneity effect-which is difficult to reconcile with the differential familiarity explanation. This study extends the latter work by hypothesising that such in-group homogeneity may be especially prevalent during the initial stages of group formation, particularly on dimensions central to the group's identity, or at other important transition points in the group's evolution. Seventy-seven student nurses in three training cohorts participated in a longitudinal study, rating their own cohort group and a variety of other categories on dimensions related or unrelated to the professional identity of nurses, and at two points in time separated by a 12-month interval. Results revealed evidence of an in-group homogeneity effect on nurse-relevant dimensions, but out-group homogeneity vis A vis doctors on a doctor-relevant dimension. Furthermore, there were several changes in the perceived variability of out-groups over time but relatively few changes in the perceived variability of the in-group. The implications of this data for some current models of perceived intragroup homogeneity are discussed.