Behavioral Economics of Persecutory Delusions

Abstract

Persecutory delusions cause significant distress in the individuals who experience them, yet as a field we are still working to understand their etiology. Persecutory delusions and suspiciousness have some overlap with mistrust, and thus this dissertation focuses on the use of trust games to examine behavior and neural mechanisms of spite sensitivity. Spite sensitivity is the fear that a partner is willing to take a hit in order to ensure that you do as well, as opposed to rational mistrust, in which a partner can make a gain but at your expense. The benefit of using social decision making tasks such as the Trust Game and its adaptation, the Minnesota Trust Game, is that 1) a computational model can be developed based on the given parameters of the task to understand beliefs and motivations and 2) it can provide a well-controlled task to examine principles of trust and spite sensitivity in neuroimaging. The goal of this dissertation is to provide evidence that spite sensitivity is an important construct to understand persecutory ideation and distrust, both in psychiatric populations but also the general population. I show that while the Trust Game identifies decreased trust in individuals with psychosis, the Minnesota Trust Game identifies that spite sensitivity is distinct from rational mistrust and can be measured computationally. Further examination in a group of individuals with psychosis show a neural dissociation between spite sensitivity and rational mistrust as well. We did not find this dissociation in a community sample of twins, yet did find a relationship between twin discordance in a computational measure of spite sensitivity and a personality measure of suspiciousness. Altogether, this dissertation provides a foundation for the use of spite sensitivity as a construct to understand persecutory ideation.