Scientific Understanding of Consciousness
Neural Basis of Economic Decision-Making
Science 13 June 2003: Vol. 300. no. 5626, pp. 1755 - 1758
The Neural Basis of Economic Decision-Making in the Ultimatum Game
Alan G. Sanfey,1,3 James K. Rilling,1 Jessica A. Aronson,2 Leigh E. Nystrom,1,2 Jonathan D. Cohen1,2,4
1 Center for the Study of Brain, Mind and Behavior, Princeton University, Princeton, NJ 08544, USA.
The nascent field of neuroeconomics seeks to ground economic decisionmaking in the biological substrate of the brain. We used functional magnetic resonance imaging of Ultimatum Game players to investigate neural substrates of cognitive and emotional processes involved in economic decision-making. In this game, two players split a sum of money;one player proposes a division and the other can accept or reject this. We scanned players as they responded to fair and unfair proposals. Unfair offers elicited activity in brain areas related to both emotion (anterior insula) and cognition (dorsolateral prefrontal cortex) (DLPFC), Further, significantly heightened activity in anterior insula for rejected unfair offers suggests an important role for emotions in decision-making.
Standard economic models of human decision making (such as utility theory) have typically minimized or ignored the influence of emotions on people's decision-making behavior, idealizing the decision-maker as a perfectly rational cognitive machine. However, in recent years this assumption has been challenged by behavioral economists, who have identified additional psychological and emotional factors that influence decision-making, and recently researchers have begun using neuroimaging to examine behavior in economic games. This study applies functional neuroimaging techniques to investigate the relative contributions of cognitive and emotional processes to human social decision-making.
The limitations of the standard economic model are effectively illustrated by empirical findings from a simple game known as the Ultimatum Game. Objecting to unfairness has been proposed as a fundamental adaptive mechanism by which we assert and maintain a social reputation, and the negative emotions provoked by unfair treatment in the Ultimatum Game can lead people to sacrifice sometimes considerable financial gain in order to punish their partner for the slight. Unfair offers in the Ultimatum Game induce conflict in the responder between cognitive ("accept") and emotional ("reject") motives, motives that we might expect to see represented in brain areas implicated in cognitive and emotional modes of thought, with additional regions possibly mediating these competing goals.
Among the areas showing greater activation for unfair compared with fair offers from human partners were bilateral anterior insula, dorsolateral prefrontal cortex (DLPFC), and anterior cingulate cortex (ACC). Activation of bilateral anterior insula to unfair offers from human partners is particularly interesting in light of this region's oft-noted association with negative emotional states. Anterior insula activation is consistently seen in neuroimaging studies of pain and distress, hunger and thirst, and autonomic arousal. This region has also been implicated in studies of emotion, in particular involvement in the evaluation and representation of specific negative emotional states. Chief amongst these are anger and disgust, both of which have been found to engage a distinct region of the anterior insula activated by an unfair offer in the present study. Though studies of disgust have largely focused on physical sensations of taste and odor, it has been suggested that emotion-based disgust (as perhaps induced by an insultingly unfair offer) may be conceptually similar. The recruitment of similar neural structures, namely the anterior insula, in both physical and moral disgust gives some credence to this notion.
In contrast to the insula, DLPFC usually has been linked to cognitive processes such as goal maintenance and executive control. Thus, the DLPFC activation we observed in response to unfair offers may relate to the representation and active maintenance of the cognitive demands of the task, namely the goal of accumulating as much money as possible.
Finally, unfair offers were also associated with increased activity in ACC. ACC has been implicated in detection of cognitive conflict, and activation here may reflect the conflict between cognitive and emotional motivations in the Ultimatum Game.
This study sought to identify the neural correlates of fairness and unfairness, and in particular the relative contributions of cognitive and emotional processes to human decision-making. A basic sense of fairness and unfairness is essential to many aspects of societal and personal decision-making and underlies notions as diverse as ethics, social policy, legal practice, and personal morality. Our results are consistent with the idea that the areas of anterior insula and DLPFC represent the twin demands of the Ultimatum Game task, the emotional goal of resisting unfairness and the cognitive goal of accumulating money, respectively. Further, our finding that activity in a region well known for its involvement in negative emotion is predictive of subsequent behavior supports the importance of emotional influences in human decision-making.
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