Definition
Oxytocin is a peptide hormone, also acting as a neurotransmitter, that the body releases during childbirth, nursing, touch, and social bonding. It earned its nickname — the "love hormone" or "cuddle hormone" — from research showing it boosts trust, generosity, empathy, and attachment.
Sapolsky uses oxytocin to puncture the assumption that any hormone is simply good. Oxytocin makes people warmer and more cooperative, but only toward those they count as their own. The very same molecule that deepens in-group affection can intensify suspicion, defensiveness, and aggression toward the out-group.
Why it matters
How it works
Oxytocin is produced in the hypothalamus and released both into the bloodstream and within the brain, where it acts on regions governing social cognition, fear, and reward. By dampening amygdala responses to familiar faces, it lowers the guard we keep up around in-group members. But because the brain so readily sorts people into us and them, that lowered guard is selective — and the heightened vigilance toward them is the flip side of the same process.