A paradigm for the study of paranoia in the general population: The Prisoner's Dilemma Game

Abstract

A growing body of research shows that paranoia is common in the general population. We report three studies that examined the Prisoner's Dilemma Game (PDG) as a paradigm for evaluation of non-clinical paranoia. The PDG captures three key qualities that are at the heart of paranoia—it is interpersonal, it concerns threat, and it concerns the perception of others' intentions towards the self. Study 1 (n=175) found that state paranoia was positively associated with selection of the competitive PDG choice. Study 2 (n=111) found that this association was significant only when participants believed they were playing the PDG against another person, and not when playing against a computer. This finding underscores the interpersonal nature of paranoia and the concomitant necessity of studying paranoia in interpersonal context. In Study 3 (n=152), we assessed both trait and state paranoia, and differentiated between distrust- and greed-based competition. Both trait and state paranoia were positively associated with distrust-based competition (but not with greed-based competition). Crucially, we found that the association between trait paranoia and distrust-based competition was fully mediated by state paranoia. The PDG is a promising paradigm for the study of non-clinical paranoia.

Keywords:

• Non-clinical paranoia
• Prisoner's Dilemma Game
• Experimental methodology

Acknowledgments

Study 1 formed part of the doctorate work of RA-C; Studies 2 and 3 part of the doctorate work of AS.

We thank BF for his help with development and validation of the SPS.

Notes

¹A potential criticism of the study is that the SPS does not capture the sense of mistrust and suspicion that people might feel when playing the PDG against a computer. If this were the case, we would expect a floor effect in participants’ scores on the SPS in the computer condition. However, there was a normal distribution of scores on the SPS among participants playing against the computer (M=15.08, SD=2.49) and with similar range of scores (9–20) as those playing another person (range = 7–23).

²Note that results for co-operation are redundant with those for distrust-based competition and greed-based competition because knowledge of any two choice alternatives allows for perfect prediction of the third alternative.