Integration of social and utilitarian factors in decision making.

Decision making is influenced by social cues, but there is little understanding of how social information interacts with other cues that determine decisions. To address this quantitatively, participants were asked to learn which of two faces was associated with a higher probability of reward. They were repeatedly presented with two faces, each with a different, unknown probability of reward, and participants attempted to maximize gains by selecting the face that was most often rewarded. Both faces had the same identity, but one face had a happy expression and the other had either an angry or a sad expression. Ideal observer models predict that the facial expressions should not affect the decision-making process. Our results however showed that participants had a prior disposition to select the happy face when it was paired with the angry but not the sad face and overweighted the positive outcomes associated with happy faces and underweighted positive outcomes associated with either angry or sad faces. Nevertheless, participants also integrated the feedback information. As such, their decisions were a composite of social and utilitarian factors.