Testosterone reactivity and reward-related brain activation in social dominance

Interpersonal relationships are an essential part of individuals, and individuals would like to be socially dominant to maximize their fitness and future well-being and access to resources. Threatening peers can achieve dominance, but dominance can be alternatively obtained by successfully taking risks and receiving tangible or social rewards from a given task. Acute testosterone increase (i.e., testosterone reactivity) is potentially independent of basal testosterone levels in explanation of social dominance, thus status-seeking or reward-seeking tendency in individuals. To examine such tendencies and their relation to the testosterone reactivity, we conducted the status-seeking task, Skydiving task (Study 1), as well as two types of the reward-seeking task, Monetary Incentive Delay (MID) task (Study 2) and Gopher task (Study 3). The results showed that a subset of the participants showed the testosterone reactivity in all three studies, which partially supports our hypothesis. As we expected, testosterone reactivity was related to the reward-related brain activity, measured by using the FRN and P300 amplitude in the Study 2 (MID Study) and reward-related brain activation in the Study 3 (PEB Study). Biological sex was associated with basal testosterone, not directly related to testosterone reactivity. Age was not linked with the testosterone reactivity in Study 1 and 2. Those results suggest that testosterone reactivity is a unique biomarker representing an individual difference, which is not much explained by the basal testosterone level. Testosterone reactivity and its link with the social dominance-related neural, behavioral, or psychosocial correlates will be worthwhile to be invested in future research