From Scientific American:
Breathing in the hormone oxytocin has been shown in recent years to trigger all kinds of feel-good emotions in people, such as trust, empathy and generosity. Now scientists find it might have a dark side: Snorting oxytocin might also incite envy and gloating. Past studies have shown that oxytocin plays a wide role in social bonding in mammals—between mates, for instance, or mother and child—and recent work suggested the hormone was linked with pro-social behavior in people, such as altruism. Still, neuroscientist Simone Shamay-Tsoory in University of Haifa in Israel and her colleagues noted that oxytocin was found to raise aggression in rodents, suggesting the hormone might play a wider role in social emotions in humans. The researchers decided to investigate envy and gloating—feelings related to the tendency to compare oneself with others—to see if oxytocin ramped up these emotions or dialed them down.
The researchers gave 56 volunteers either oxytocin or a placebo and paid them to take part in a game of chance with another participant which, unknown to them, was a computer. They were shown three doors on a video screen, either red, blue or yellow, and told that behind each door was a different sum of money they could keep after the game.