Speculation about effects of intergroup contact dates back to the nineteenth century and studies on the topic started as early as the 1930s (Pettigrew & Tropp, 2005). In this field, Allport’s (1954) work has shown to be most influential. Ever since its formulation, his contact hypothesis has inspired hundreds of studies (Pettigrew et al., 2011). In a meta-analysis of more than 500 of these studies, Pettigrew and Tropp (2006) concluded that the hypothesis is generally supported and that the conditions set by Allport (equal status, institutional supports, common interests and the pursuit of common goals) turn out to be facilitating, indeed. As such, it is worthwhile to quote Allport (1954, p. 281) here at length:
Prejudice (unless deeply rooted in the character structure of the individual) may be reduced by equal status contact between majority and minority groups in the pursuit of common goals. The effect is greatly enhanced if this contact is sanctioned by institutional supports (by law, custom or local atmosphere), and provided it is of a sort that leads to the perception of common interests and common humanity between members of the two groups.