Want to know the formula for happiness? According to Paul Ekman, a psychologist at the University of California at San Francisco, the answer's simple: 12+6 AU. This may seem a tad technical, and indeed it is: Ekman's numbers correspond to physiology not feeling. His Facial Action Coding System (FACS) measures the movements of the forty-odd muscles in the face; and as far as he's been able to determine, the closest we come to pure delight is with a combination clench of the zygomatic major (the grin muscles, or Action Unit 12) and the orbicularis oculi (the muscles surrounding the eye, or Action Unit 6). Sadness may be defined just as crisply: 1+4+6+11 AU. In plain English, that means "the inner corners of the brows drawn together and upward, cheeks raised, slight deepening of the nasolabial fold, and slight depression of the lip corners."

Ekman's obsessive mapping of the human face is part of a Darwinian quest to prove that facial expressions are hardwired, largely involuntary, displays of human affect. A new Oxford anthology co-edited by Ekman, What the Face Reveals, offers a gallery of tantalizing FACS experiments that support his claim. While some of the results are not exactly surprising--for example, a lurch of Action Unit 5, the "eyelid raiser," turns out to be the key signal for surprise--other FACS research suggests that frame-by-frame scrutiny of the face can pick up fleeting visual cues that otherwise get lost in real-time conversations. Despite our best intentions to suppress or conceal our emotions, it seems they're written all over our face--whether we like it or not.

The FACS system is laborious but simple: All possible facial movements, from the everyday (blinks, nose wrinkles) to the exotic (lip compressions, cheek puffs), are assigned a classification number between 1 and 46. Through careful notation of photographs and video stills, FACS researchers can chart a subject's changing facial landscape. By comparing observed facial patterns with subjects' self-reports of emotional states, FACS researchers claim to have isolated characteristic expressions for seven discrete emotions--anger, fear, contempt, disgust, sadness, surprise, and happiness.

Ekman himself is a distinguished pioneer in the field of evolutionary psychology. Back in the Sixties, he started out his career as a disciple of B.F. Skinner, who argued that emotions were mere "unobservables" and thus not worthy of serious inquiry. As for facial expressions, behaviorists viewed them as arbitrary gestures learned in infancy through reward and punishment. Ekman set out to prove this notion by contrasting the facial repertoires of Americans with those of the Fore, an isolated Papua New Guinean tribe. But the Fore refuted the behaviorist thesis: When asked to act out a humorous story, tribespeople began flashing Kodak smiles; when describing frightening hunting tales, they adopted Hitchcockian poses. As Ekman says now, "I was dead wrong, and it was the most exciting discovery of my life."

So Ekman turned to Darwin, who in 1872 penned a monograph called The Expression of the Emotions in Man and Animals, which argued that "the same state of mind is expressed throughout the world with remarkable uniformity." While Ekman recognizes the role of culture in establishing "display rules"--social values that dictate when it's appropriate to smile in public, for example--he nonetheless insists that facial gestures have fixed biological underpinnings. In the anthology, Ekman cites a study comparing the expressions of American and Japanese toddlers who were physically restrained for several minutes. FACS reveals that both sets of impeded tots display the same group of Action Units associated with anger.

What are the implications of this universalist thesis? Try as we might to mold our emotional displays, Ekman suggests, involuntary responses keep leaking through. "To me, an emotion can't be fully masked," says Ekman. "We can't feel something intensely and not show it at all." This insight has led some researchers to use FACS as a sort of subliminal-message decoder. Take Ekman's famous case study of "Mary," a suicidal patient who manipulated her therapists into granting her release from the hospital. Just before leaving, she admitted her deception. Fortunately for Ekman, Mary's false statements at the exit interview had been videotaped. Using FACS, he determined that her underlying despair was, however briefly, written on her face: "In a moment's pause before replying to her doctor's question about her plans for the future, we saw in slow motion a fleeting facial expression of despair, so quick that we had missed seeing it the first few times we examined the film. Once we had the idea that concealed feelings might be evidenced in these very brief micro expressions, we searched and found many more, typically covered in an instant by a smile."

FACS has uncovered numerous "slips of the face." In a related essay on suicide faces, the Swiss psychologists Michael Heller and Veronique Haynal describe FACS experiments that reveal significant differences in facial expressions between suicidal and non-suicidal depressed patients. The two researchers interviewed residents of a Geneva psychiatry ward, half of whom had recently attempted to kill themselves. A FACS analysis was conducted to analyze nonverbal responses to the question "Do you still wish to take your own life?" The results were unexpected: Most of the suicidal patients displayed flashes of contempt and disgust when answering the question, while none of the non-suicidal patients did.

Other researchers have used FACS as a facial polygraph. How can one tell a genuine smile from a false one? According to several papers in the anthology, the telltale sign of a genuine smile isn't a wide grin but a deep eye scrunch. These "felt happy smiles," one Ekman-led study notes, typically feature "apex coordination," with the eye closure reaching its maximum intensity at the same time the grin reaches its fullest height. Real smiles are also shorter and smoother in execution than anxious or faked varieties. One can only imagine what HMOs could do with such a diagnostic tool.

And yet FACS itself is hardly perfect. According to one paper, faked lower-back pain looks just like the real thing to FACS. "This is a frustrating finding," admits Ekman. "But while the face is a key signal system, there are others, like the voice and gestures, that may have more pivotal roles with certain emotions." Similarly, attempts to venture beyond the Big Seven emotions have proved tricky; one of the most recent papers in the anthology suggests that embarrassment is evinced not through a "snapshot expression" but rather through a sequence of movements (most prominently, lip compression, Action Unit 24) combined with gestures like lowering the face. And FACS may never be able to pinpoint exact patterns for emotions like jealousy or disappointment.

Another barrier to progress is FACS's speed. At present, five minutes of videotape takes around twelve hours to transcribe. Fortunately, Terry Sejnowski, an artificial intelligence theorist at San Diego's Salk Institute, is working with Ekman to develop a computerized neural network that will almost instantly translate a facial image into a list of Action Units. According to Ekman, "it should be up and running within five years." The 400 psychologists currently certified to use FACS must be salivating. After all, when reading a face becomes as easy as making one, who knows what they'll uncover?

Daniel Zalewski

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