It may be hard to believe, but your college yearbook photo might provide the most accurate insight into how happy you are with your life today, says University of California, Berkeley, psychologist Dacher Keltner, PhD.

In one of Keltner's most well-known studies of human emotion, he and colleague LeeAnne Harker, PhD, coded the smiles of 110 women who graduated from Mills College in 1960, based on the contractions of two facial muscles—the zygomatic major, which pulls the lip corners up, and the orbicularis oculi, which surrounds the eyes. He found that the women with warmer smiles in their yearbook photos—that is, stronger contractions in these two muscles—reported being more content with their lives 30 years later.

He also found that these women were also more likely to have accomplished their goals, reported less anxiety on a daily basis and were happier in their marriages (Journal of Personality and Social Psychology, Vol. 80, No. 1).

Keltner, director of the Greater Good Science Center, an interdisciplinary research center based at Berkeley, is the author of the book, "Born to Be Good: The Science of a Meaningful Life" (W.W. Norton & Co., 2009).

How is it that we can glean so much information from a half-second smile or momentary eyebrow shift?

It's thanks to evolution. The body is an amazingly powerful and rich medium of communication. It signals our deepest emotions, and because so many of the most important social interactions in human life and in our evolution are really brief and fast—be it flirting with someone amid a bunch of strangers or rescuing an offspring who's catapulting toward a source of danger—we've evolved the powerful ability to communicate our current states really fast. So when we measure such states scientifically, like in our yearbook photo study, by coding facial expression, vocalization or patterns of touch, you get this remarkably faithful assessment of who a person is and what they're feeling.

What have you found about non-verbal behaviors among romantic partners?

Romance and long-term bonds are built on a few basic emotions. One is the dizzying sexual passion often really pronounced early in a relationship. Another is this poignant long-term love that you feel for someone you live a life with. The thinking in evolutionary terms is that those emotions do different things. One gets us to reproduce, because without that, our species doesn't go very far. The other helps us form pair bonds.

We wondered if people reveal emotions such as sexual desire or long-term love in little changes in facial appearances. We had romantic partners come into the lab and recorded them talking about how they fell in love, and then we gathered data from them about how much they loved each other, whether they felt sexually attracted to each other, whether they were committed.

In the non-human primate world, prior to copulation, partners lick and pucker their lips and protrude their tongues. Lo and behold, little half-second bursts of lip puckers and lip licks in our human subjects correlated with feeling sexually attracted to their partner and being happy sexually. In contrast, in the primate world, tender warmth is signaled by head tilts and open-handed gestures and warm smiles, and sure enough, in our human couples, we found that little one-second bursts of those behaviors correlated with feeling love and wanting to get married and talking about a long-term life together.

In a second study, we had women talk about an experience of love or warmth and we assessed oxytocin release in the bloodstream, a neurochemical that promotes devotion, long-term pair bonding, trust, sacrifice and generosity. Sure enough, the more the women showed these warm, open-handed gestures and smiles and head tilts, the more we saw oxytocin get released into the bloodstream, whereas the degree to which they showed sexual desire in their faces—in lip licks or puckers—bore no relationship to oxytocin release. So in analyzing very specific behaviors that are expressed for just a second or two, we can start to pull apart long-term love versus momentary sexual desire.

What has your research revealed about how touch can communicate emotion?

Up until about five years ago, the study of human emotion had been anchored to the face and to a lesser extent, the voice. We haven't fully studied other modalities of communication. So a former student, Matt Hertenstein, came to my lab and said, "I wonder what emotions you can communicate just by touching a person?"

So Matt and I brought people into the lab and separated them by a barrier so they couldn't see or hear each other and we had them try to communicate different emotions just by a touch to the forearm. What we found was really quite remarkable: You can communicate emotions like anger, fear and disgust just with one-second touches, and in fact you can communicate emotions like sympathy, gratitude and love much more powerfully through touch than through the face.

We also found some pretty provocative gender differences. We had all possible gender combinations in this research in terms of who was the toucher and who was the touchee, and the only differences we saw were that when a woman tries to communicate anger through touch to a man, he can't figure out what she's doing, and when a man tries to communicate sympathy to a woman, she has no idea what he's doing. We think this might have to do with how women are socialized into the ways of sympathy and how they occupy more caretaking roles. They probably develop a richer vocabulary in touch for sympathy, and men have trouble with that. Men get a richer socialization into anger and aggression, and that means women may have trouble communicating that emotion through touch.

What research is still needed with regard to positive emotions?

We know a lot about the physiological processes related to stress, anxiety and anger and how these emotions shorten our lives and harm our immune system and our organs. But we don't yet know what effects emotions such as compassion and a sense of beauty and awe have in the long run in terms of resilience and health. These kinds of questions represent enormous opportunities for the field, to understand how positive emotions are embodied in our nervous systems, and how they enable more meaningful lives.

We're also starting to generate data showing that when positive emotions like compassion and pride are activated, they stimulate different regions of the brain than emotions like anger and disgust. That work starts to, in a very early sense, tell a story about the genetically encoded physiological underpinnings of positive emotions.

What about your work might psychologists find most surprising?

Psychologists tend to think of our core human design as being about fight-or-flight tendencies and about the bad in human nature. But in fact it may be the case that the most recent shifts in our evolution are toward these more cooperative, positive emotions. It's intuitive for people to say that human nature is evil or dark or violent or aggressive, and when you hear about the continuing struggles of the Israelis and the Palestinians, or you hear about the latest genocide, you say, well, that's just what human beings are—that's our natural state. Our studies reveal that the good stuff in human nature—sympathy, gratitude, awe, laughter—are just as clearly part of our natural state and readily explained by evolutionary principles and built into the human design.

What makes this work so important today?

We're in a deep period of cultural reflection right now in terms of our values, our economy and our relationship to the environment. My take is what we've lost sight of are a lot of these important social emotions, which the data say are the paths to the good life and happiness and being more modest in our use of resources and being more generous. I hope this new science of altruism and human goodness stimulates a broader conversation about the place of emotions like compassion and awe in our lives.

How can psychologists use your research to tackle some of these ongoing challenges?

Part of our task as psychologists is just to understand this complex organism, the human being. But I've always felt that our science is only as good as the people who put it into practice. For example, we know how important compassion and touch are to our human nervous system, and work by Darlene Francis here at Berkeley shows that touch calms stress-related physiology in rat pups and that it's good for their immune systems. We're now learning that physicians are taking this science of compassion and gratitude and touch and they're learning how to be more empathetic doctors.

New scientific findings show that the more patients feel a compassionate connection to their doctors, the longer they live in the face of disease. That is just one on-the-ground application of this new science of positive emotions. I see enormous hope in where the science will go in shaping our society.