Cooperation and psychopathy: A game-theoretic perspective

Abstract

In the last century, academics have focussed on understanding how we make decisions and they have proven through lab and web experiments that people do not always follow a purely rational process. Contrariwise, several exogenous and endogenous mechanisms have been found to influence our decision-making patterns, leading us towards cooperative behaviours, even when personal costs are involved. In this thesis, I investigate how a specific aspect of personality, namely psychopathic traits, affects cooperative actions in different scenarios, employing both primary and secondary experimental data. Furthermore, I explore the beneficial and detrimental role of some of the most defining dimensions of psychopathy in the evolution of a population through an individual-based model.

Firstly, I address the topic by analysing the data of two laboratory experiments previously conducted. Both experiments examine the influence of psychopathic traits in an iterated Prisoner’s Dilemma game, with the presence of opponents emotional facial feedback. While in the first experiment those feedbacks are purely contextual, in the second one they are manipulated to investigate their effects on cooperation, while controlling for psychopathic traits. Results from the first experiment show a negative marginal effect of a dimension of psychopathy, namely disinhibition, on cooperative actions. In the second experiment, higher levels of fearless dominance have a negative influence on cooperation over time, although the presence of emotional facial feedbacks does not affect the level of cooperation. Moreover, I find a positive correlation between psychopathic measures and the adoption of defective strategies in the game. Thus, this first part of the thesis sheds light on the interaction of psychopathic traits and the presence of emotional stimuli received from the opponent after each decision.

Both these experiments investigate the effects of psychopathic traits on decision-making from an individual point of view. In the second part, I approach the subject from a group level view. I designed and conducted a laboratory experiment examining the influence of the presence of relatively high psychopathic individuals in groups on the level of cooperative actions. The main result is that, independent of individuals own psychopathic measures, belonging to a group with a larger number of high psychopathic people leads group members towards less cooperative behaviours. This second part approaches the study of decision-making and psychopathic traits iii by investigating group dynamics, providing new interesting results on group composition and cooperation, as well as an innovative experimental design to investigate group decisions.

Lastly, I model the evolution of a population composed by two main agents types, one of which incorporates some of the most characteristic feature of psychopathy (such as selfishness and risk-seeking attitudes). Relying on empirical findings, I developed an individualbased model mimicking the evolution of a population under different environmental conditions. Through this model, I examine the beneficial and detrimental effects of individuals with selfish and risk-seeking over several generations: while they can be harmful in situations of prosperity, they become helpful, if not essential, in periods of hardship.

This thesis inspects the role of psychopathic traits in decision-making processes from a wide range of perspectives. Doing so, it enables the reader to have a comprehensive understanding on how this specific dimension of personality shapes both individual and group cooperation in different scenarios, and how psychopathic individuals can be (or not) evolutionarily adaptive.

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Identifiers

ORCID for Rebecca Hoyle: orcid.org/0000-0002-1645-1071

ORCID for Hedwig Eisenbarth: orcid.org/0000-0002-0521-2630

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