THE MORAL MOLECULE
Paul J. Zak's proclivity for taking blood samples has earned him a nickname as the vampire economist. But his sanguinary habit is backed by his scientific quest: What if there was a master switch for human behavior? On, and people are loving and generous. Off, and they revert to violence and greed. By studying thousands of blood samples, Zak has pinpointed just such a switch: a brain chemical called oxytocin.