What Is Love? Evolution and Infatuation

Valentine's Day is all about love. But what, exactly, is that?

Helen Fisher is an anthropologist at Rutgers University in New Jersey and author of several books on love, including Why We Love: The Nature and Chemistry of Romantic Love.

Fisher breaks love into three distinct brain systems that enable mating and reproduction:

• Sex drive
• Romantic love (obsession, passion, infatuation)
• Attachment (calmness and security with a long-term partner)

These are brain systems, not phases, Fisher emphasized, and all three play a role in love. They can operate independently, but people crave all three for an ideal relationship.

"I think the sex drive evolved to get you out there looking for a range of partners," she said.

"I think romantic love evolved to enable you to focus your mating energy on just one at a time, and attachment evolved to tolerate that person at least long enough to raise a child together as a team."

Valentine's Day, Fisher added, used to encompass only two of these three brain systems: sex drive and romantic love.

But "once you start giving the dog a valentine, you are talking about a real expression of attachment as well as romantic love."