The reality and evolutionary significance of human psychological sex differences

Abstract

The aims of this article are: (1) to provide a quantitative overview of sex differences in human psychological attributes, and (2) to consider evidence for their possible evolutionary origins. Sex differences were identified from a systematic literature search of meta-analyses and large-sample studies. These were organized in terms of evolutionary significance as follows: (1) characteristics arising from inter-male competition (within-sex aggression; impulsiveness and sensation-seeking; fearfulness; visuospatial and object-location memory; object-centred orientations); (2) those concerning social relations that are likely to have arisen from women’s adaptations for small-group interactions and men’s for larger co-operative groups (person-centred orientation and social skills; language; depression and anxiety); (3) those arising from female choice (sexuality; mate choice; sexual conflict). There were sex differences in all categories, whose magnitudes ranged from (1) small (object location memory; negative emotions), to (2) medium (mental rotation; anxiety disorders; impulsivity; sex drive; interest in casual sex), to (3) large (social interests and abilities; sociosexuality), and (4) very large (escalated aggression; systemizing; sexual violence). Evolutionary explanations were evaluated according to whether: (1) similar differences occur in other mammals; (2) there is cross-cultural consistency; (3) the origin was early in life or at puberty; (4) there was evidence for hormonal influences; and (5), where possible, whether there was evidence for evolutionarily derived design features. The evidence was positive for most features in most categories, suggesting evolutionary origins for a broad range of sex differences. Attributes for which there was no sex difference are also noted. Within-sex variations are discussed as limitations to the emphasis on sex differences.