Immunizing against prejudice: effects of disease protection on attitudes toward out-groups.

Contemporary interpersonal biases are partially derived from psychological mechanisms that evolved to protect people against the threat of contagious disease. This behavioral immune system effectively promotes disease avoidance but also results in an overgeneralized prejudice toward people who are not legitimate carriers of disease. In three studies, we tested whether experiences with two modern forms of disease protection (vaccination and hand washing) attenuate the relationship between concerns about disease and prejudice against out-groups. Study 1 demonstrated that when threatened with disease, vaccinated participants exhibited less prejudice toward immigrants than unvaccinated participants did. In Study 2, we found that framing vaccination messages in terms of immunity eliminated the relationship between chronic germ aversion and prejudice. In Study 3, we directly manipulated participants' protection from disease by having some participants wash their hands and found that this intervention significantly influenced participants' perceptions of out-group members. Our research suggests that public-health interventions can benefit society in areas beyond immediate health-related domains by informing novel, modern remedies for prejudice.