The "cuddle hormone" oxytocin [2] gets all the attention, but a new study finds that other chemicals in the brain may play even bigger roles in people's interactions with others.

In the study, researchers looked at people's genes for six different "social neuropeptides" — chemicals in the brain that are involved with social interactions — and found that two have particularly large effects on relationships.

"There are a number of chemicals in the brain that play an important role in predisposing us to behave in particular ways," said senior study author Robin Dunbar, a professor of evolutionary psychology at the University of Oxford in England. [11 Interesting Effects of Oxytocin [3]]