Testosterone responses to competitive interactions and facial displays of emotion: a social neuroendocrinology perspective

Testosterone levels are not static but fluctuate in response to environmental inputs, including social signals. Acute changes are particularly observed in response to evolutionarily salient social interactions such as antagonistic encounters and exposure to potential mates. The overarching goals of this dissertation are (1) to examine whether facial displays of emotions are effective social behavioral signals that modulate testosterone (Study 1); (2) to better understand the interplay between motivational, situational and physiological factors in shaping androgen release in competitive situations (Study 2 and Study 3); and, (3) to investigate the short-term and longer-term functional consequences of testosterone responses to competition (Study 3). In Study 1, I found that both men and women had an increase in testosterone when exposed to faces of the opposite sex, while only women had an additional increase in testosterone when presented with angry faces. In Studies 2 and 3, I found that testosterone responses to shifts in social status (win vs. loss) (1) were modulated by situational (i.e. familiarity of the task and number of competitions) as well as physiological (i.e. basal levels of cortisol) factors, and (2) had long-term – but not short-term- functional consequences on behaviors related to the competitive task. These results are discussed within a comparative perspective, drawing parallels with the Competition Effect, the Winner Effect and the Challenge Hypothesis observed in non-human animals. Possible evolutionary mechanisms underlying these phenomena are discussed as well.