Heterosexual males are reported to display higher levels of physical aggression and lower levels of empathy than homosexual males. A characteristic linked to both aggression and empathy is social dominance orientation (SDO). A significant sex difference has been reported for SDO, with heterosexual males scoring higher than heterosexual females. The precise relationship between dominance and aggression is currently contested. Given the association between SDO, aggression and empathy, and the differences between heterosexual and homosexual males, an analysis of how sexual orientation co-varies with SDO might help to clarify the association between aggression and dominance. SDO scores were derived from heterosexual males (n = 60), heterosexual females (n = 60) and homosexual males (n = 60). Heterosexual males reported higher levels of SDO than heterosexual females and homosexual males, while heterosexual females scored higher than homosexual males. These differences were analogous for physical aggression. More work is required to thoroughly understand the aetiology of these effects as well as the strategic value of the behaviours, but for now we have reason to further investigate the organizational hormone hypothesis put forward in this paper.
Evolutionary adaptation in variable environments is likely to give rise to several signals that can be used to identify a suitable mate in multisensory organisms. The presence of multiple signals for sexual selection could be advantageous, limiting the chance of mating with a suboptimal partner and avoiding the costs of inferior progeny. Despite extensive research into isolated signals of attractiveness, the amalgamation of multiple signals in sexual selection is poorly understood, particularly in humans. Inferences regarding both the function and importance of such signals are therefore tentative unless the effects are considered together. Here, the literature regarding two evolved signals of attraction (cf. faces and voices) is reviewed in relation to a framework (Candolin 2003) for signal integration. It is argued that the functional nature of signals of attractiveness would be better studied through manipulation and experimentation with both single and multiple signals. Considering the prevalence of traits in relation to their combined effects may well provide a more fruitful and informative approach to human mate selection.