Does diversity actually change people's prejudices, or just their options?

Researchers tracked friendship choices across 228 classrooms to test whether exposure to different ethnicities, genders, and social classes reduces prejudice. Using a statistical model that accounts for the actual pool of available peers, they found that for most categories, students' underlying preferences stayed the same—diversity just created more opportunities to befriend people they wouldn't otherwise meet. For gender, however, preferences actually strengthened toward same-gender peers as classrooms became more mixed, supporting conflict theory over the optimistic contact-hypothesis.