Saliva has testosterone and estrogen. When you kiss, you're having a chemical experience.

People compose poetry, novels, sitcoms - for love.

We spend our lives trying to get along with people so we can keep our jobs, keep our marriages together, so that we can raise our kids properly.

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

Romantic love is not an emotion. ... It's a drive. It comes from the motor of the mind, the wanting part of the mind, the craving part of the mind.

There's magic to love... Millions of years ago we evolved three basic drives: the sex love, romantic love, and attachment to a long-term partner. These circuits are deeply embedded in the human brian. They're going to survive as long as our species survive on what Shakespeare called, this "mortal coil."

From my studies of genetics and neuroscience I have come to believe that people fall into four broad personality types - each influenced by a different brain chemical: I call them the Explorer, Builder, Director, and Negotiator.