Frederike Petzschner

Frederike Petzschner

Brown University

Agency Beliefs and Credit Assignment

Room 636 NYU Meyer Hall, 4 Washington Place

Abstract

The judgement that an action is worth performing at all rests on a belief of agency: that what one does bears some reliable relation to what one obtains. Beliefs of this kind, concerning the efficacy of one’s own agency, are neither uniform across individuals nor stable within them, and their distortions are distributed across much of the psychiatric spectrum. At one pole lies the depressive conviction that no available action will alter the course of events; at the other, the compulsive conviction that a particular action, however arbitrary its relation to the feared outcome, must nevertheless be performed lest catastrophe ensue. I argue that these apparently opposite phenomena are better understood as two expressions of a single computational problem, that of assigning credit for observed outcomes to the actions that may or may not have produced them. The first half of the talk concerns disordered gambling. We show how the illusion of control, an expectancy of personal success in excess of what the objective probabilities warrant, inflates both the magnitude of wagers and subjective estimates of winning under conditions determined by chance alone, and how the systematic misattribution of wins to skill rather than to fortune sustains compulsive play. The second half addresses credit assignment more directly. Here we examine how beliefs about action-outcome contingency give rise to repetitive behaviour in healthy participants and in obsessive-compulsive disorder, where actions are repeated despite evidence that they contribute little to the outcomes they are intended to secure.