Better-than-chance prediction of cooperative behaviour from first and second impressions.

Could cooperation among strangers be facilitated by adaptations that use sparse information to accurately predict cooperative behaviour? We hypothesise that predictions are influenced by beliefs, descriptions, appearance and behavioural history available for first and second impressions. We also hypothesise that predictions improve when more information is available. We conducted a two-part study. First, we recorded thin-slice videos of university students just before their choices in a repeated Prisoner's Dilemma with matched partners. Second, a worldwide sample of raters evaluated each player using videos, photos, only gender labels or neither images nor labels. Raters guessed players' first-round Prisoner's Dilemma choices and then their second-round choices after reviewing first-round behavioural histories. Our design allows us to investigate incremental effects of gender, appearance and behavioural history gleaned during first and second impressions. Predictions become more accurate and better-than-chance when gender, appearance or behavioural history is added. However, these effects are not incrementally cumulative. Predictions from treatments showing player appearance were no more accurate than those from treatments revealing gender labels and predictions from videos were no more accurate than those from photos. These results demonstrate how people accurately predict cooperation under sparse information conditions, helping explain why conditional cooperation is common among strangers.

Gender, Stereotypes, and Trust in Communication.

Gender differences in dishonesty and mistrust have been reported across cultures and linked to stereotypes about females being more trustworthy and trusting. Here we focus on fundamental issues of trust-based communication that may be affected by gender: the decisions whether to honestly deliver private information and whether to trust that this delivered information is honest. Using laboratory experiments that model trust-based strategic communication and response, we examined the relationship between gender, gender stereotypes, and gender discriminative lies and challenges. Drawing from a student sample, we presented males and females (N = 80) with incentivized stereotype elicitation tasks that reveal their expectations of lies and challenges from each gender, followed by a series of strategic communication interactions within and between genders. Before interacting, both genders stereotyped females as more trustworthy (expected to send more honest messages) and more trusting (expected to accept and not challenge others' messages) than males, in accord with cross-cultural gender differences. In best response to these stereotypes, both genders discriminately accepted or challenged messages based on the sender's gender. However, we find no differences between males' and females' overall rates of lies and challenges. After learning the results of their strategic interactions, males and females revised their stereotypes about lies and challenges expected of each gender; these stereotype revisions resulted in greater predictive accuracy and less disparate gender discrimination. This suggests an important facultative feature of human trust-based communication and gender stereotyping: while the delivery and trust of private information is informed by gender stereotypes, these stereotypes are recalibrated with experience.