Contact theory, sometimes called the contact hypothesis, suggests that contact between members of different groups can improve relations between them if the contact occurs under certain conditions. For more than 50 years, this theory has been important in influencing expectations [Page 446]regarding the social outcomes of schools with diverse student bodies and in suggesting factors likely to influence whether experiences in such schools improve intergroup relations. So, for example, Thomas F. Pettigrew distinguishes between schools he characterizes as integrated, because they serve diverse student populations and meet contact theory's conditions, and those he characterizes as merely desegregated, that is, merely racially or ethnically mixed, suggesting that the former improves intergroup relations but the latter might not do so.