Leda Cosmides: UC Santa Barbara

According to the alliance detection hypothesis, racial categorization is a (reversible) byproduct of cognitive mechanisms that evolved for detecting social alliances (Kurzban, Tooby & Cosmides, 2001; Pietraszewski, Cosmides & Tooby, 2014). In southern California, showing subjects a single social interaction in which race is uncorrelated with alliance patterns produces a sharp decrease in racial categorization. But what happens in Brazil, where the social history linking race with alliance patterns is different? We conducted tests in seven Brazilian states that differ radically in their racial composition. Social class is a major dimension along which alliances are formed, and these states differ in the extent to which race predicts social class. Across states, the extent to which categorization by race decreased in response to alliance cues was highly correlated (r = .97) with the cue validity of race for predicting that targets were of the same social class as the subjects.