Oxytocin and vasopressin, two hormones that inspire feelings of love and generosity when they flood our brains, bind to neurons by attaching to molecules called receptors, which can come in different forms. The new research, led by psychologist Michel Poulin of the University of Buffalo, suggests that if you have the genes that give you certain versions of those hormone receptors, you’re more likely to be a nice person than if you have the genes for one of the other versions. However, the researchers found that the genes work in concert with a person’s upbringing and life experiences to determine how sociable — or anti-social — he or she becomes.

As detailed in a new article in the journal Psychological Science, hundreds of people were surveyed about their attitudes toward civic duty, their charitable activities and their worldview. They were asked, for example, whether people have an obligation to report crimes, sit on juries or pay taxes, whether they themselves engage in charitable activities such as giving blood or volunteering, and whether people — and the world as a whole — are basically good, or are threatening and dangerous. Of those surveyed, 711 people provided a sample of their saliva for DNA analysis, which showed which version of the oxytocin and vasopressin receptors they had.