Sex differences in cognitive ability are modest (McCarthy & Konkle, 2005). Patterns of social interaction typically show much stronger contrast, extending in varying form and degrees of magnitude across species. In general, species having the greatest differences in roles in procreation tend also to have the most marked behavioral differences (McCarthy, 2008). In humans and most other mammalian species, females have generally been characterized as being more sensitive to social cues and stresses, such as perception of rejection. Evolutionarily this has been tied to adaptation of social roles to facilitate bearing offspring and having primary responsibility for care of the very young, including the capacity for attunement needed to foster cognitive and social development of the neonate (Cyranowski, Frank, Young, & Shear, 2000). The relationship of the sex differences in brain development described by the neuroimaging studies above to these functional differences in social behavior is as yet largely unexplored. It is intriguing to speculate that a better understanding of the neurodevelopmental processes underlying sex differences in social cognition may also provide a key to another functional aspect of sex
