Individuals' neural circuitry predicts their prosocial motives

Grit Hein, Yosuke Morishima, Susanne Leiberg, Sunhae Sul, and Ernst Fehr

Previous social science research has identified different prosocial forces, reaching from 
emotions such as empathy to social motives such as reciprocity. However, attempts to 
uncover the motive behind an actual prosocial act have been of little success. Here we 
show that the motive that drives a personŐs prosocial behavior can be identified on the 
basis of information about an individual's neural circuitry captured by DCM parameters. 
Participants made the same set of prosocial decisions either driven by an empathic or a 
reciprocal motive that we controlled experimentally. We measured each individual's DCM 
parameters and submitted them to a classification algorithm that identified the two 
underlying motives with high accuracy, thus uncovering whether a personŐs decision had 
been driven by empathy or reciprocity. Our results further indicate that the empathic 
motive consolidates the neural underpinnings of basic prosocial motivation, whereas the 
reciprocal motive activates additional processes related to impression formation and 
action selection. Finally, we show that the empathic motive is more effective in 
increasing prosocial behavior in relatively selfish individuals compared to the reciprocity 
motive. These findings provide neurobiological foundations for the driving forces of 
human prosociality.