Trust, morality -- and oxytocin?

(NOTE: Research and statements in this talk have been challenged by other scientists working in this field. Please read "Criticisms & Updates" below for more details.) What drives our desire to behave morally? Neuroeconomist Paul Zak shows why he believes oxytocin (he calls it "the moral molecule") is responsible for trust, empathy and other feelings that help build a stable society.