Romantic love is an addiction: a perfectly wonderful addiction when it's going well, and a perfectly horrible addiction when it's going poorly.

There's a lot of talk about the positive aspects of love. We as a society downplay the danger, the anxiety, and the disappointment. We romanticize romance.

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

Until recently, we regarded love as supernatural. We were willing to study the brain chemistry of fear and depression and anger but not love.

Men tend to be hierarchical, but women are driven to make lateral connections so they can cooperate.

Men and women are like two feet; they can help each other get ahead.

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.