Large sex differences in children's toy preferences are attributed to gender group identification and social learning. The proposal outlined in this paper is that contemporary conceptual categories of "masculine" or "feminine" toys are also influenced by evolved perceptual categories of male-preferred and female-preferred objects. Research on children exposed prenatally to atypical levels of androgens and research on typically developing infants suggest sex-dimorphic preferences exist for object features, such as movement or color/form. The evolution and neurobiology of mammalian visual processing--and recent findings on sex-dimorphic toy preferences in nonhuman primates--suggest further that an innate bias for processing object movement or color/form may contribute to behaviors with differential adaptive significance for males and females. In this way, preferences for objects such as toys may indicate a biological preparedness for a "masculine" or "feminine" gender role-one that develops more fully as early perceptual preferences are coupled with object experiences imposed by contemporary gender socialization.