When chimps threaten, they open their mouth and show their teeth. It's a little like waving a knife in front of you. It's very primitive, and therefore bizarre.

There are cognitive processes and limbic reactions associated with basic emotions. And you can change brain chemistry, but you're still not going to change memories and experiences in a human being.

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

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.

In America, we are demanding everything from our marriage.

In general, men are wired to notice obvious signs that convey interest in mating - a warm smile, for example - and ignore other subtleties, like if your lipstick is faded.

Kissing is not just kissing. It is a major escalation or de-escalation point in a powerful process of mate choice.