You fall in love with somebody who fits within what I call your 'love map,' an unconscious list of traits that you build in childhood as you grow up. And I also think that you gravitate to certain people, actually, with somewhat complementary brain systems.

If we remained perpetually infatuated, we couldn't eat, sleep or work.

Hair that gleams can send a clear sign that you're young and in your prime, whatever your actual age.

When you fight, anger drives up testosterone in both men and women.

Women apparently are quite drawn to men who have differences rather than similarities in their histocompatibility system. They pick it up by smell, and they can pick it up from kissing.

Blushing is thought to be linked to increased levels of norepinephrine in the brain, which may be associated with romantic feelings. It signals that we are interested and excited, which is attractive to men.

Office romances are few, short, and not usually destructive.