In the first study, 34 elementary school students were evaluated to determine their attitude toward immigrants (often stigmatized in Italy) and then divided into two groups that read passages from Harry Potter for six weeks under the guidance of a research assistant. The test group read the scenes that describe prejudice (mudbloods, house elves etc. If that doesn’t make sense to you, you should read the books), while the control group read passages without themes of prejudice. After the last session the children who identified the most with the character Harry and read the prejudice-related passages were shown to have significantly improved attitudes toward immigrants whereas the opinions of the children in the control group had not changed.
A second, similar study was conducted with high-school students and demonstrated an improved attitude toward homosexuals in the test group. The third was conducted among university students regarding their attitudes toward refugees with the same results.