Helen Fisher

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.

The Great Depression of the 1930s saw more American unmarried women working from nine to five, mostly in repetitive, boring, subordinate, dead-end jobs. But the number of working women doubled between 1870 and 1940. During World War II it doubled once again.

When you massage someone, the levels of oxytocin go up in the brain, and oxytocin is one of the chemicals that drives attachment.

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

You know, when you've been dumped, the one thing you love to do is just forget about this human being, and then go on with your life - but no, you just love them harder.

Whether you're married or not, relationships - and the satisfaction tied to them - are extremely important for increasing men's and women's quality of life.

Sometimes we fall in love with somebody who will probably never love us, for reasons having nothing to do with us but with their own mindset, their chemistry.

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.

We all have restlessness in long-term relationships.

The reason you take antidepressants is to feel calm. And romantic love is not calm - it's elation, it's mood swings, and you're killing all that when you take the drug.

At first I assumed hate was the opposite of love. But it isn't. The opposite of love is indifference.

Women are naturally prone to compete over their mates.