Whenever the hormone oxytocin makes the news—and it does so regularly—the media can’t help but refer to it as the “love hormone”, “cuddle chemical” or “moral molecule”. Few substances enjoy such a positive public profile. Oxytocin, it is said, is at the core of all our virtues, from trust to empathy to cooperation.

This rose-tinted view is a sham.

The latest example of this comes from Shaul Shalvi and Carsten de Dreu. They found that people who sniff oxytocin become more dishonest in a simple team game, but only if their lies benefit their group. If they play the game alone, oxytocin doesn’t change their behaviour for better or for worse. As de Dreu says, “This is the best evidence yet that