From private attitude to public opinion: A dynamic theory of social impact.

A computer simulation modeled the change of attitudes in a population resulting from the interactive, reciprocal, and reeursive operation of Latan~'s (198 I) theory of social impact, which specifies principles underlying how individuals are affected by their social environment. Surprisingly, several macrolevel phenomena emerged from the simple operation of this microlevei theory, including an incomplete polarization of opinions reaching a stable equilibrium, with coherent minority subgroups managing to exist near the margins of the whole population. Computer simulations, neglected in group dynamics for 20 years, may, as in modern physics, help determine the extent to which group-level phenomena result from individual-level processes. Writing about social phenomena, social scientists have produced empirical generalizations and theoretical analyses of social processes representing differing levels of social reality. Some analyses concern the cognitions, feelings, and behavior of individuals; others deal with small, medium, or large groups, collectivities, and organizations; still others involve such largescale human aggregates and systems as nations, societies, or cultures. Theories can be and are formulated and tested independently for phenomena at each of these levels, but one can also ask about the relations between mechanisms operating at different levels (Doise, 1986; Kenny, 1987; Nowak, 1976). These relations may be of two kinds. The functioning of higher level units (e.g., social groups) may be partly or completely determined and therefore explained by mechanisms known from theories describing phenomena at lower levels (e.g., human individuals). Alternatively, the functioning of lower level units (e.g., individuals) may be affected by the higher level units to which they belong. In other words, individuals in a given social context behave differently than they would outside that context. These relations, taken together, suggest that the interactive impact of individuals and their social context can result in the emergence of new regularities at the levels of both the individual