Testosterone and emotion expression shape social interactions in defection-cooperation conflicts

Emotions and hormones such as testosterone crucially shape social interactions, including cooperation. However, whether testosterone regulates the impact of emotional expressions in defection versus cooperation conflicts remains elusive. The present study determined the effects of single-dose testosterone administration on cooperative behavior and emotional expression in the prisoner’s dilemma game (PDG). Sixty-one healthy young males received either a 125 mg dose of testosterone gel or placebo in a double-blind, placebo-controlled design and subsequently underwent a modified PDG paradigm including emotional expressions. Testosterone increased the likelihood to defect when facing defection, yet enhanced cooperation when both players cooperated. Notably, when exposed to negative emotions from their counterparts, testosterone-treated individuals reacted with a higher proportion of Emoji 4 (commonly conveying strong negative emotions). Findings underscore the crucial interaction between testosterone and emotional cues on social interactions and indicate a social context-specific role of testosterone.