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Just by watching Barack Obama walk down the stairs with George W. Bush last month, Helen Fisher, a research professor of anthropology at Rutgers University, knew what kind of president he’d be—and what kind of mate he is. Fisher is the author of the best-selling Why We Love and chief scientific adviser to the dating site Chemistry.com. Her new book, Why Him? Why Her? (Henry Holt) describes four archetypal human temperaments—the risk-taking “Explorer,” the cautious, traditionalist “Builder,” the competitive, analytical “Director” and the empathetic “Negotiator”—and how they interact personally, romantically and even professionally.

Look at John McCain’s face, he’s got the jaw, the heavy brow ridges and the high forehead of the high-testosterone type, the Director.

You say you’re interested in “nature’s patterns of mate choice.” What do you mean by that?

Psychologists know that we gravitate toward people who are from the same socio-economic background, same general level of intelligence and looks and religious and social values. But you can walk into a room where everyone shares those traits with you, and you don’t fall in love with all of them. Why is that? We’ve been looking for explanations in childhood, in relationships to your parents, which we know must be important, but we haven’t found the patterns yet. Maybe they exist but we haven’t found them.

I’m a biological anthropologist. My research convinced me that we have evolved four broad personality styles, a constellation of temperament traits, each associated with different brain systems. And I drew the hypothesis that maybe when you walk into a room full of people who could be plausible mates, you are drawn to some rather than others because of this biology. I just couldn’t believe that four million years of evolution would be so lax as to let us choose our partners on whim.

And the pattern you found is…

We saw this pattern where the Explorer goes for the Explorer, the Builder goes for the Builder, and the Director and the Negotiator are attracted to one another. And it doesn’t matter if you’re male or female. Of course this is just a matter of degree. We’re all a mix of all of them, which is why I describe people with both a primary and a secondary type.

The book reprints a questionnaire you used in your research, that readers can take to determine which type they are. But even if you know what you are, you can’t run the test on someone you’ve just met at a party. So what are people supposed to take away from this?

Well, let me tell you what I got from it. I finally understand people. I’ve been working on romantic love and pair-bonding for 30 years and I finally understand why we’re rather magically drawn to some people and not to others. I would like people to understand who they are, and why they love the person that they love, how to reach the person, how to make some changes in your own style—on a date, or in a relationship, or with a boss or with your children.

So this principle is about more than just romance.

By far. I understand Obama, I understand his wife…I don’t want to be presumptuous here, but when you understand nature’s patterns, you see them play out over and over.

And what type is Obama?

I think he’s an Explorer/Negotiator. For a black man to seek the presidency, he’s clearly a risk-taker. He’s got a lot of curiosity, he’s creative in the way he addresses problems and handles people. I also think he’s a Negotiator, because he’s caring. This man cares about the whole world. He was trying to improve the South Side of Chicago as a young men when he could have gone to Wall Street and made a million bucks. He has wonderful verbal skills and people skills.

Two traits he has that indicate elevated activity in the dopamine system, which relates to the Explorer: He has a very expressive face, and he moves with a style…watching him and Bush walk down the stairs to the helicopter, he walked gracefully, like an Explorer would, and Bush lumbered down.

And Bush is…?

I think he is a Builder/Director. He has that intense need for loyalty. That’s in the serotonin system. He’s religious, stubborn, uncreative.

I know those are predominantly negative-sounding traits. I don’t want to malign Builders. They have some wonderful characteristics too. George Washington was a Builder.

I’ve actually gotten extremely interested in history because now, I understand history better. Boris Yeltsin was an obvious Explorer: impulsive, charming, alcoholic, but at the right moment he leapt onto a tank and gave a speech that changed the course of his country. A cautious Builder might have hesitated.

You didn’t give them your test, obviously. How do you know that, as you say in your book, Einstein was “a classic Director” or that Darwin was a Negotiator

From their biographies, of course, and their words and even their faces. Look at John McCain’s face, he’s got the jaw, the heavy brow ridges and the high forehead of the high-testosterone type, the Director. And when he was conceding, the front page of The New York Times had a picture of him holding his hands up, and sure enough, his fourth finger was longer than his second. That’s a dead giveaway of more testosterone. The man was a fighter pilot, for heaven’s sake. He must have used the word “fight” 43 times in his acceptance speech.

Your data about attraction is drawn from a sample of people on the Chemistry.com site, so it measures initial attraction, not long-range happiness or satisfaction. How do you know these relationships will last?

Psychologists have known for a long time that you tend to make up your mind about someone in the first three minutes. That decision guides the trajectory for years to come. Initial attraction is a very important moment. It’s not an idle moment that I’m measuring, it’s a very profound point in a relationship.

And what about Helen Fisher? You’re an Explorer—have you found another one?

I’m still looking for him.

Have you ever been married?

I was married when I was 23, and divorced when I was 23.

He wasn’t an Explorer?

Not enough of one.

Jerry Adler is a contributing editor at Newsweek, where he writes about medicine, science, and ideas. He is the author of High Rise: How 1,000 Men and Women Worked Around the Clock for Five Years and Lost $200 Million Building a Skyscraper.

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