Experiments have shown that simply by dividing individuals into groups and identifying them with labels, systemic "discrimination" is produced against the out-group. Further, that once there is an in- and out-group distinction (when there is also direct competition and rivalry), the out-group will be the target of hostility and negative attitudes and behavior. These destructive attitudes and actions subsequently become general norms . . . . Thus are social categories made to be culturally problematic.Constance Perin, Belonging in America: Reading Between the Lines (Madison: Univ. of Wisconsin, 1988) (pp. 124-125, citing Robin M. Williams, review of Towards the Elimination of Racism, by Phyllis A. Katz, Ed Science 192: 660-662 [14 May 1976]).