The Contact Hypothesis (hence, "CH") is an old idea in social psych: That contact between groups reduces prejudice. This was one central theme of Allport's 1954 classic The Nature of Prejudice, built on even earlier ideas.
1. The effects hover near 0.
2. The one exception is for contact w/ppl w/disabilities. Remove that, and the results are still above 0 (ie, *some* effect of conctact), BUT: