When researchers at the University of Buffalo and University of California, Irvine, set out to look into the neurogenetics of being nice, they went about collecting a few things: first, answers to several survey questions, such as, "Are people basically good or bad?," and "Do you donate blood? Go to PTA meetings?" Next, they asked surveyers to spit.

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After analyzing the answers and the saliva, they found that some people have receptors that are especially sensitive to the hormones oxytocin and vasopressin, and that those people did nice things even when their survey answers revealed that they generally feared others in society.

"We’ve found that these genes also predict people’s willingness to be nice on behalf of other people or aggressive on behalf of other people," study co-author and assistant professor of psychology Michael Poulin told CNN.

Past tests have shown people to be nicer after receiving squirts of oxytocin in their noses. And without the extra sensitivity to those hormones, this study revealed that people who perceive the world as threatening did not participate in charitable activities.

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The study, published in this month's Psychological Science, doesn't give you a free pass to blame your DNA for being mean, Poulin said. The study shows a an association between genes, hormones and behavior; not a direct causal link.

"While we found some interesting interactions with genes and perceptions of the world, I would resist saying that we found genes that control behavior," he said. "We aren't saying we've found the niceness gene. But we have found a gene that makes a contribution."

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