Sexual selection and trust games

Abstract

In economic games the facial attributes of counterparts bias decisions to trust and decisions to enter play. We report research supporting hypotheses that trust and reciprocation decisions in trust games are biased by mechanisms of sexual selection. Hypotheses that trust game behaviour is modulated by inter-sexual competition were supported. 1) Attractive individuals elicit more cooperation. 2) Male participants display trust and reciprocation toward attractive female counterparts in excess of perceived trustworthiness (and this display is modulated by male self-reported physical dominance). 3) Female participants appear to respond to male trust as a signal of sexual interest and are therefore more likely to exploit the trust of attractive males. 4) In explicitly dating contexts females are more likely to prefer attractive males to pay for the meal. These results indicate that participants are biased by mate choice and mating display considerations while playing economic games in the lab. Hypotheses that trust game behaviour is modulated by intra-sexual competition for resources were also somewhat supported. 1) Male participants reporting an ability to win fights with same-sex peers are more exploitative of other males. 2) Cues to current circulating testosterone level in counterpart’s faces are less trusted but elicit more reciprocation. 3) The male sexually dimorphic trait facial width-to-height ratio (a trait which is related to both aggression and dominance) is related to an increased proportion of decisions to exploit others in the trust game while also being used by others as a cue to untrustworthiness. We conclude that trusting and trustworthy behaviour in both sexes is biased by mating market considerations predicted by intra- and inter-sexual selection.