Humans are driven by a variety of needs, motives, and goals. Dating back to the early part of the twentieth century, researchers have attempted to understand human behavior by linking behavior to underlying motiva-tions(e.g., Hull, 1943; Spence, 1956). In line with this tradition of exam-ining human behavior within the framework of individual goals and motivations, researchers studying group
... [Show full abstract] behavior and intergroup relations from a social identity perspective (e.g., Tajfel & Thrner, 1979, 1986) recognized that multiple motives may operate in a group context. Behavior is driven not only by realistic concerns (e.g., conflicts over resources), but also by individuals' desire for positive social identity. In answer to the question of why individuals identify with groups (particularly minimal groups that appear to hold little significance for group members), Thrner (1975) argued that "subjects will identify with a social category to the extent that such identification enables them to achieve value significance, to the extent that it is the category most relevant to the "desire for positive self-evaluation" (pp. 19-20). Thus, the social identity approach to inter-group relations has always incorporated the concept of needs and motives for understanding intergroup behavior. However, what has been missing to some extent from earlier formulations of social identity theory (SIT: Tajfel & Thrner, 1979, 1986; Turner, 1975) and self-categorization theory (SCT: Turner, Hogg, Oakes, Reicher, & Wetherell, 1987) is an integration of the variety of individual needs (beyond positive distinctiveness) that might come into play within group contexts and how these needs might interact with cognitive and structural variables to produce particular patterns of intragroup and intergroup behavior. The goal of the current chapter is to address the issue of how individual needs and motives influence identification processes and group behavior Assimilation and Differentiation 57 by focusing on two particular needs -the need for assimilation and the need for differentiation -that have comprised the bulk of our research in this area. We will begin by describing research suggesting that these needs represent core human motivations. We then tum to the subject of how these needs can be satisfied within groups and the implications that these needs have for understanding social identity and group processes. In reviewing our work in this area, we hope to convey that the complexity of intragroup and intergroup behavior requires an understanding of both the external factors (e.g., group status, group size) present in a given context and the internal factors (e.g., personal appraisals, needs, personality) that can vary widely among individuals within that context. Assimilation and differentiation as fundamental human needs