# A Model of Risk and Mental State Shifts during Social Interaction

## TL;DR

This paper enhances the I-POMDP framework to better model social risk, trust dynamics, and emotional responses like irritation in repeated trust games, providing insights into social behavior and disorders.

## Contribution

It introduces improved inference methods for I-POMDPs, modeling social risk-aversion and irritation, and applies them to analyze human behavior in trust games.

## Key findings

- Identified social risk-aversion in control players.
- Modeled irritation and anger affecting cooperation.
- Demonstrated relevance in healthy and patient cohorts.

## Abstract

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. This offers the prospect of particular insight into populations of subjects suffering from socially-debilitating conditions such as borderline personality disorder. However, although a suitable foundation for the quantitative analysis of such games exists, namely the Interactive Partially Observable Markov Decision Process (I-POMDP), computational considerations have hitherto limited its application. Here, we improve inference in I-POMDPs in a canonical trust game, and thereby highlight and address two previously unmodelled 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 exhibited by both players. Irritation arises when partners apparently defect, and it 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.