Biological influences on human social behavior Bernd Weber Life & Brain Center, Bonn & Center for Economics and Neuroscience, Bonn Social preferences are important determinants of social behavior and vary largely between individuals (e.g., reciprocity, altruism). This talk will focus on several studies investigating the biological basis of individual differences in social behavior applying different neuroscientific methods. The first two studies will show influences of social comparison processes on reward-related brain activity (Fliessbach et al., 2007, 2012). I will go on to present a study where we investigated motives in charitable donations (Kuss et al., 2012) and hormonal influences on cheating behavior (Wibral et al., 2012). Finally, I will present brain-structural correlates of interindividual differences in social behavior (Cohen et al., 2009).