Sharon Barnhardts jobmarket paper, "Near and Dear? Evaluating the Impact of Neighbor Diversity on InterReligious Attitudes" undersöker ett intressant fall i Indien:

I exploit a natural experiment in a large Indian city in which Hindus and Muslims were randomly assigned units in a public housing complex with physically distinct "clusters" of four units. The lottery generates exogenous variation in the degree of religious diversity across clusters within the complex.

Resultaten:

Greater exposure to Muslims (the minority group) improves Hindus' explicit attitudes about Muslims by 0.25 to 0.40 standard deviations, depending on the measure, and increases their willingness to live with Muslims. Paralleling this, I observe significant reductions in implicit bias against Muslims (0.20 to 0.57 standard deviations) among Hindu children

En annan studie, "Interaction , prejudice and performance . Evidence from South Africa" (Burns et al) med randomiserad kontext ger också en del upplyftande resultat:

We exploit random assignment of roommates in double rooms at University of Cape Town to investigate whether interaction with a person of a different race affects inter-ethnic attitudes, cooperative behavior and academic performance.

Resultaten:

living with a roommate of a different race significantly reduces white students’prejudice towards blacks[...]. The reduction in stereotypes is accompanied by a more general tendency to cooperate, as measured in a prisoner’s dilemma game and by participation in volunteering activities. Finally, we show important effects of the policy on academic outcomes: blacks who share the room with non-black students significantly improve their GPA, pass more exams and have a higher probability to continue university. The positive effect on performance among black students is not driven by the ability of the roommate and is stronger the lower the degree of prejudice of the roommate. [min markering av sista meningen]

En tredje randomiserad studie (Scacco & Warren i APSR) visar inte på några positiva effekter av blandade grupper, men däremot på negativa effekter av homogena grupper.

Kontexten:

an education-based, randomized field experiment—the Urban Youth Vocational Training program (UYVT)—with 849 randomly sampled Christian and Muslim young men in riot-prone Kaduna, Nigeria.

Resultaten:

After sixteen weeks of positive intergroup social contact, we find no changes in prejudice, but heterogeneous-class subjects discriminate significantly less against out-group members than subjects in homogeneous classes. We trace this finding to increased discrimination by homogeneous-class subjects

När det gäller kontakthypotesen generellt, finns en ofta citerad survey av Pettigrew och Tropp’s (2006) som drog följande slutsats:

With 713 independent samples from 515 studies, the meta-analysis finds that intergroup contact typically reduces intergroup prejudice. Multiple tests indicate that this finding appears not to result from either participant selection or publication biases, and the more rigorous studies yield larger mean effects.

En uppföljning (publicerad i somras) av denna översikt, som fokuserade på randomiserade studier bekräftade bilden:

Building on Pettigrew and Tropp’s (2006) influential meta-analysis, we assemble all intergroup contact studies that feature random assignment and delayed outcome measures, of which there are 27 in total, nearly two-thirds of which were published following the original review. We find the evidence from this updated dataset to be consistent with Pettigrew and Tropp's (2006) conclusion that contact "typically reduces prejudice."