Integrating approaches requires more than a division of labour: commentary on Wӧlfer & Hewstone

Wӧlfer and Hewstone (2015; hereafter W&H) argue that evolutionary psychology (EP) is useful for understanding sex differences in same-sex aggression, while social role theory (SRT) is best applied to sex differences in opposite-sex aggression. W&H tested this proposal using a rich dataset on high school students’ peer-reported aggression. They regressed classroom-level sex differences in same- and opposite-sex aggression onto five variables drawn from the two theoretical positions. Three variables (gender and masculinity norms, derived from SRT and body dimorphism, derived from EP) did not differ in their association with the two forms of aggression. Another variable (sex ratio: EP) was not interpretable because it was confounded with number of available targets, leaving a fifth (male hierarchy: EP) predicting sex differences in same-sex but not opposite-sex aggression. Our focus is not on the study itself, but on their proposal that theoretical disputes between EP and SRT can be resolved by assigning one form of aggression to EP and another to SRT. We believe that this argument mischaracterises both theories, reinforces the ‘evolutionary vs social’ divide, and falls short of integration.