According to one definition, a race is a group of individuals who share some common physical characteristics that distinguish them from other individuals in the species. Although members of different races are members of the same species and can breed together, some kind of separation usually geographic has prevented them from doing so for some period. During that period, the distinctive differences between the groups emerged. This definition implies that differences between groups are based in biological differences. In adults, individuals with an authoritarian personality appear to have high levels of negative prejudices about other groups.
Authoritarian personalities emphasize control, rules, and discipline.
Many of the most extreme racist doctrines of the past have been based on the assumption of biological differences between groups. Controversy over these issues, such as whether genetic differences between groups are the cause of group differences on IQ test scores, still swirls through academic and public debates. Scientists generally believe that this concept of race as based on biological differences does not fit the case of human groups. Biological distinctions are quite minor compared with the commonalties at the biological level. The majority of the variation occurs within groups.