What makes us attractive — or not?

What's in a face? David Perrett has spent his career trying to find out.

The author of "In Your Face: The New Science of Human Attraction" (Palgrave Macmillan, 2010), Perrett is an experimental psychologist at the University of St. Andrews in Scotland and head of its Perception Lab. Using computer graphics, Perrett's team tweaks faces on-screen to explore how they help us choose the best mates, whether you can trust a face, the cuteness factor in babies and what faces reveal about overall human health.

We tend to be egotistical creatures, he says; when people smile, we tend to think they are smiling at us, but when they look angry, we think they are mad at someone else. We like attractive faces turned toward us, and less attractive faces turned away from us. But then, he notes, our brain chemistry can break all the rules and make us drawn to one person, even if that person's visage is not perfect.

Perrett spoke with The Times about his work.

The work in your lab has produced some general rules of attractive faces. What are they?

One rule is symmetry — it does make faces more attractive. But it's a small factor. Another rule is averageness. That may seem contradictory, but we like to choose things that are familiar to us.

Another rule applies to female faces: You can make them more attractive [in computer models] by making them more feminine. For instance, you can make lots of structural changes — taking a broader chin and more prominent eyebrow bones and changing them to a smaller chin and a less prominent eyebrow bones. You can also create a smaller nose and larger eyes. In male faces, you can make them more rugged or masculine, but not all women will agree that the increased masculinity is more attractive.

There are also clues to health in the face. For instance, skin color — this is not about dark skin or light skin, but rather about redness and yellowness. Ruddiness can tell you about the blood circulation, whether it's poor or good. Yellowness in the skin reveals a plant-based diet.

Do people seek symmetrical partners?

Everyone seems to like symmetry, but not everyone likes it as much. For instance, women who find themselves attractive seek more symmetrical men. So the degree to which symmetry matters to someone depends on what they think of themselves.

Symmetry is less important to some people; it actually explains very little about the range of attractiveness in people.

Your research also reveals that not everyone plays by the same rules or focuses on the same things. Can you talk about that?

Beauty is in the eye of the beholder. There are so many reasons why we're attracted to one face versus another. The family — particularly parents — affects us. Especially if we get along with our parents, we tend to (but don't always) choose partners that resemble the opposite-sex parent.

There's also a lot of social learning from peers. If we see our peers giving a lot of attention to one person, then that person might become more appealable in our eyes. We can see that in the influence of Hollywood stars.

The experiences you have with someone — friendship or more intimate — really affects how you see them. No matter what their face, the chemicals in our brain can lock us onto one person.

You have also charted attractiveness over time. You've written: "We're at our cutest at about 8 months of age, and after that it's all downhill." Explain.

One way to chart this is to play around with faces of babies [on the computer]. You can expand the forehead and reduce the size of the chin.

By 8 months of age, human babies have a massive forehead and a really diminutive chin — and that's the point at which most people find babies most attractive. After 8 months, the face grows relatively quickly. That gives rise to a less and less cute configuration. We find infants cute and we want to take care of them.

But, of course, there are different types of "attractive" — for instance, sexual attraction after puberty.

You also observe that "a good-looking son could come from any dad, whether the dad was good-looking or not." Why?

There is a widely believed idea in biology called "sexy sons" — that good-looking sons will father the most offspring, and that what is attractive to women in one generation will be attractive to women in the next generation.

We found that masculine dads do have masculine sons. But some women like masculine men and some women don't like it. So that's why there's no connection between father[s] and sons.

Can you talk about the evolutionary forces that caused our faces to look the way they do?

Because we move forward in the environment, it makes sense for the sense organs — ears, nose, mouth — to be in the front.

The biggest evolutionary change is that we transformed from animals shuffling around in the night to daytime creatures — you move from dependence on smell to navigate at night to high-quality vision during the day. Our noses aren't nearly as important as our visual sense in the daytime, and so our noses are scaled back and smaller. And using vision goes hand in hand with using facial expressions. We began to use our facial muscles for calls and expressions — we see this in monkeys that signal to each other with postures and head signals. Most other mammals can hardly move their faces for a range of expression. Whereas we can move our faces expressively and pick up on subtle communications.

This interview was edited for space and clarity from a longer discussion.


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