Some researchers would examine your brain anatomy to answer this question... and it's exactly what a team of scientists from the University of Zurich in Switzerland have done. The researchers conducted a study to investigate the neurobiological causes of altruistic behavior. To do so, participants were asked to share some money with a stranger. The team found that the most altruistic subjects, i.e those who shared the most money, were also those with more gray matter at the junction between the parietal and temporal lobes. These results help the scientists understand which biological factors determine a person's tendency to altruism. Nonetheless, it is not to forget that such behavior can also be explained by other factors such education or cultural background.