Abstract:
Altruistic behaviors can be defined as those actions which are costly to self, beneficial to
another, and do not convey a benefit from reputation or reciprocity on the part of the
recipient. Behaviors which meet these criteria are widely observed in behavioral
experiments utilizing the dictator game. It has been suggested altruists may receive direct
utility in the form of "warm glow" which offsets the cost of their behavior. Alternatively,
it has been suggested that social norms exist which supporting reciprocity and reputation,
the salient features of those norms are reproduced in the experimental setting, and
altruism will decrease over time as subjects gain experience in the experimental
environment. We explore other-regarding behavior while subjects undergo functional
magnetic resonance imaging in the context of a modified dictator game where money
cost is either replaced or augmented with effort cost. We find behaviorally that subjects
are willing to exert effort to benefit their counterpart, but will not expend money, even
when the cost to the subject is trivial compared to the gains available to the counterpart.
Neurologically, we find evidence that superior-temporal regions and temporo-parietal
junction is active when subjects observe reward accruing to the counterpart but not to
self. These regions are frequently implicated in theory of mind tasks where subjects must
imagine the mental state of another individual, and in social contextual knowledge tasks,
where subjects must access and utilize norms proscribing appropriate conduct in social
settings. Our results suggest that regions of the brain associated with social knowledge
and interaction are required to interpret those outcomes associated with other-regarding
behavior, even in the context of a one-player game where social interaction is absent.
This activation pattern is more consistent with a theory that other-regarding behavior is
modulated by social norms than the "warm glow" of utility directly experienced from
increased payments to the counterpart.
