Klinische Neurophysiologie 2012; 43 - P066
DOI: 10.1055/s-0032-1301616

A reward prediction error for charitable donations reveals outcome orientation of donators

K Kuss 1, K Fliessbach 1
  • 1Center for Economics and Neuroscience, University of Bonn, Bonn

Objective: The motives underlying charitable donations are much debated and one striving question is whether people care about the outcome of charitable donations (outcome-orientation). Another motive discussed in this context can be regarded as action-oriented: people care about the act of giving per se (action-orientation). We tested for outcome orientation by investigating if brain activity in the NAc covaries with the amount of donated money.

Methods: While lying in an MR scanner, subjects (N=33) made 180 decisions affecting their own payoffs and payoffs to a charity organization. In order to test the subjective value of a chosen outcome half of the decisions was discarded, the other half was confirmed. This manipulation implemented two reward prediction errors (RPE), one with regard to subjects’ payoff, the other with regard to the charity’s payoff. Data analysis focused on brain activity in the nucleus accumbens (NAc) during the decision phase and at the time-point of the RPE induction (2 parametric regressors: subject’s RPE regressor, charity’s RPE regressor in ascending order).

Results: Subjects were classified into donators (n=16) and non-donators (n=17) based on their willingness to give up own monetary advantages in favor of the charity organization during the experiment (costly donations). We did not find an effect of different decision types on NAc-activity during the decision phase of the experiment. However at the point of RPE induction there was a strong signal in the NAc reflecting the RPE for the subjects’ own payoff in the entire subject group. For the subgroup of donators there was a significant signal reflecting the RPE for the charity’s payoff in the same location.

Conclusions: This result provides strong evidence for outcome orientation of donators and is a unique demonstration of a RPE signal for a payoff concerning unrelated others.

Acknowledgements: This study was funded by the German Research Council (Grant FL715/1–1)