We're apt to fall in love with those who are mysterious and challenging to us.

Hair that gleams can send a clear sign that you're young and in your prime, whatever your actual age.

Romantic love is an addiction.

The Internet lets women use words, which is their natural tool. Little girls speak in more complex, grammatical sentences than little boys do, and women never lose that superiority in verbal ability.

Hair that looks like it's been naturally sun-bleached makes you seem youthful, like you spend a lot of time outdoors. And that appeals to most people.

Jealousy can even be good for love. One partner may feel secretly flattered when the other is mildly jealous. And catching someone flirting with your beloved can spark the kind of lust and romance that reignites a relationship.

As a group, anthropologists are not too fond of people who work in the business world.