Does Exogenous Testosterone Modulate Men's Ratings of Facial Dominance or Trustworthiness?

Previous research indicates that men's testosterone levels, or personality and contextual variables known to influence testosterone levels, predict men's attributions of social and personality characteristics from faces. However, the correlational nature of many of these past findings precludes our ability to establish causal pathways. Here, across two pharmacological challenge experiments, we examined the extent to which testosterone reduced men's perceptions of trustworthiness from emotionally-neutral faces (Experiment 1, N = 30, within-subjects design) or sensitivity to dominance from men's faces that varied in characteristically dominant shape (Experiment 2, N = 117, between-subjects design). Results from Experiment 1 showed that administration of testosterone did not significantly lower men's perceptions of trustworthiness. An unexpected order effect (i.e., drug x order of administration interaction) showed that trustworthiness ratings were higher after testosterone, but only if men received testosterone on the first day and placebo on the second day; importantly, this effect was directionally opposite to that reported in the literature and to that predicted for the present study. Experiment 2 demonstrated that dominance perceptions did not vary as a function of whether men received testosterone or placebo. Supplementary analyses with linear mixed effects generally support the main findings across experiments, but also provide more nuanced details involving exploratory individual difference variables. Results from the present experiments provide important information to a growing body of research examining testosterone and complex social processes, and may help inform future research on the topic.