UNMASKING RECIPROCITY: Behavioral components and neural correlates of human trustworthiness

Abstract

Trust-repayment behavior is crucial to establish and maintain cooperative links between different (even genetically unrelated) individuals. However, neither the exact nature of this behavior considered mainly as reciprocity, an intentions-based behavior), nor its underlying neural basis, re clear. My research used behavioral economics games designed to measure reciprocity (the Investment game) and altruism (the Dictator game), in addition to electroencephalography, to investigate the processes that occur in the brain during trust-repayment behavior. Unlike other similar studies, the experimental setup I used monitored the behavior and brain activity during the Dictator and Investment games in the same individual and session. This allowed me to identify differences that are specifically due to altruism versus reciprocity. My results show that measuring reciprocity together with altruism enables me to distinguish between positive and negative reciprocity, constructs “hidden” when reciprocity is measured without assessing altruism. Furthermore, I found that subjects’ neural activity differs when they evaluate an allocation received in a Dictator versus an Investment game, triggering different frontomedial negativities that could reflect differences in (i) cognitive control requirements in altruistic, outcome-based behaviors, and in (ii) subjects’ valuation of trust in reciprocal, intentions-based behaviors. In addition, my results show that subjects’ psychopathic traits interact with expectation-related brain activity in the mentalizing network, thus modifying how subjects respond to trust.