Q. Isn't love a basic human emotion?

A. Romantic and parental love are more enduring than emotions, though they are highly emotionally laden. I don't just feel happy with my daughter. Sometimes I'm worried, sometimes I'm surprised, and sometimes I might feel anger. It's an attachment, not a fleeting emotional state. A mood, by the way, is different still. It doesn't last as long as an attachment, though it can last for hours or even longer.

Q. More than 100 years ago, Charles Darwin proposed that human facial expressions are universal. Anthropologists like Margaret Mead thought the opposite. What do you think?

A. Initially, back in 1965, I thought Margaret Mead was probably right. But I decided to get the evidence to settle the argument. I showed pictures of facial expressions to people in the U.S., Japan, Argentina, Chile and Brazil and found that they judged the expressions in the same way.

But this was not conclusive because all these people could have learned the meaning of expressions by watching Charlie Chaplin and John Wayne. I needed visually isolated people unexposed to the modern world and the media.

I found them in the highlands of Papua New Guinea. They not only judged the expressions in the same way, but their posed expressions, which I recorded with a movie camera, were readily understandable to people in the West.

Q. One of your most fascinating findings is that if a person merely arranges his face into a certain expression, he will actually feel the corresponding emotion. In other words, emotions work from the outside in as well as the inside out. Is happiness really as simple as putting on a happy face?

A. In a very limited way, yes. The trick with happiness is that while everybody can smile, most people can't move one crucial muscle around the eyes that must be moved to generate the physiology of happiness. With anger or disgust, though, everybody can make the right facial movements and turn on the physical sensations of those emotions.