For men, being too put-together implies femininity.

My hypothesis is that conservative Republicans have very clear values, and when you have that, you're simply more relaxed.

Once you fall for someone, their smell can be a powerful thing. Women will wear their boyfriends' T-shirts, and throughout tales in history men have held on to their lover's handkerchief.

There exists no culture in which adultery is unknown, no cultural device or code that extinguishes philandering.

When somebody leaves Match.com or Chemistry.com, they ask you why you left. One box you can check is, 'I found somebody.' Between 15 and 20 percent of people check that box.

Overdone lipstick is a deterrent to men. It rubs off easily onto their skin and the edges of their shirts, so it discourages them from kissing, touching, and coming closer to you, which is what they really want to do!

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.

Young women today do not marry the men they met in high school, or even the one they go out with at college, because they do not need to.

Your sweetheart calls you by another's name. His eyes linger too long on your best friend. He talks with excitement about a girl at work. And the fire catches. Jealousy - that sickening combination of possessiveness, suspicion, rage, and humiliation - can overtake your mind and threaten your very core as you contemplate your rival.

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.

Both sexes like the exercise and challenge of sports, but for men it's also a basic display behavior for impressing and winning a mate.

You've got to remember that men are men and women are women. And although a lot of similarities, there are some real differences.

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

It certainly would have been adaptive for ancestral man to have a chubby wife during stressful times of famine. Not only would she have had more calories to burn, and thus more energy and endurance, but since fat stores estrogen, she would have remained fertile for longer.

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

The human brain is built to compare; it's Darwinian to consider an alternative when one presents itself.

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.

When you look at the brain regions associated with picking up data from the body, a huge amount of the brain is devoted to picking up information from the lips and tongue.

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.

There is more and more data indicating that there is a biological basis to your political views.

Mothers really were not built to raise babies not only by themselves, but with only a partner. For millions of years, a woman had much more than just her husband to help rear her young... This whole idea of 'it takes a village to raise a child' is exactly how we're supposed to live.

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

Research shows that couples who have a lot of similarities, including intellectual compatibility, end up staying together.

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