A Model of Risk and Mental State Shifts during Social Interaction
Montague, P. Read
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Cooperation and competition between human players in repeated microeconomic games offer a powerful window onto social phenomena such as the establishment, breakdown and repair of trust. However, although a suitable starting point for the quantitative analysis of such games exists, namely the Interactive Partially Observable Markov Decision Process (I-POMDP), computational considerations and structural limitations have hitherto limited its application, and left unmodelled some critical features of behavior in a canonical trust task. Here, we extend the I-POMDP framework and also improve inference. This allowed us to address two phenomena: a form of social risk-aversion exhibited by the player who is in control of the interaction in the game, and irritation or anger, seen as a shift of their internal state, exhibited by both players. Irritation arises when partners apparently defect, and it potentially causes a precipitate breakdown in cooperation. Failing to model one’s partner’s propensity for it leads to substantial economic inefficiency. We illustrate these behaviours using evidence drawn from the play of large cohorts of healthy volunteers and patients.