The Neuroeconomics of Distrust: Sex Differences in Behavior and Physiology.

Trust is an essential component of transactions that occur over time. The amount of trust accorded to others is typically conditioned on multiple factors, including knowledge of the other party, the history of interactions, and the context of exchange. Determining who to trust and who to distrust is especially important in modern societies with largely impersonal exchange (Vernon L. Smith, 2003). In fact, trust is among the strongest predictors of whether a country will successfully develop: poor countries are by-and-large low-trust countries. This occurs because low trust inhibits investment and thereby the creation of wealth (Zak and Stephen Knack, 2001). Unfortunately, subjects in laboratory settings are unable to articulate clearly why they decide to trust or distrust a trading partner. In order to discover why human beings trust or distrust others, economists have begun obtaining physiologic measurements during trust experiments (Zak, 2005). This new transdisciplinary field is called neuroeconomics (Kevin McCabe et al., 2001; Zak, 2004; Colin F. Camerer et al., 2005). Recently, Zak et al. (2004, 2005) reported that people who received a signal of trust in an experimental game had higher levels of the neuroactive hormone oxytocin (OT) than those who received similar amounts of money absent a trust signal. In addition, higher OT levels were associated with an increased reciprocation of trust (i.e., greater trustworthiness). Animal models have shown that OT promotes prosocial behaviors by producing a pleasurable sensation. Because humans are highly social creatures, there may be both positive and negative physiologic controls over social behaviors, as there are for other important behaviors. For example, the hormones ghrelin and leptin are primary regulators of nourishment, promoting food intake and signaling satiety to terminate food consumption, respectively. This paper provides evidence for a hormone that is associated with a negative social interaction, distrust. We test two hypotheses: