Human faces pop up on a screen, hundreds of them, one after another. Some have their eyes stretched wide, others show lips clenched. Some have eyes squeezed shut, cheeks lifted and mouths agape. For each one, you must answer this simple question: is this the face of someone having an orgasm or experiencing sudden pain? “The assumption for a long time was that facial expressions were obligatory movements,” says Lisa Feldman Barrett, a psychologist at Northeastern University in Boston who studies emotion. In other words, our faces are powerless to hide our emotions. The obvious problem with that assumption is that people can fake emotions, and can experience feelings without moving their faces. Researchers in the Ekman camp acknowledge that there can be considerable variation in the ‘gold standard’ expressions expected for each emotion. … According to Jessica Tracy, a psychologist at the University of British Columbia in Vancouver, Canada, researchers who conclude that Ekman’s theory of universality is wrong on the basis of a handful of counterexamples are overstating their case. One population or culture with a slightly different idea of what makes an angry face doesn’t demolish the whole theory, she says. Most people recognize an angry face when they see it, she adds, citing an analysis of nearly 100 studies. “Tons of other evidence suggests that most people in most cultures all over the world do see this expression is universal.” Read the whole story: Nature More of our Members in the Media > … At one extreme, the group cited studies that found no clear link between the movements of a face and an internal emotional state. Psychologist Carlos Crivelli at De Montfort University in Leicester, UK, has worked with residents of the Trobriand islands in Papua New Guinea and found no evidence for Ekman’s conclusions in his studies. Trying to assess internal mental states from external markers is like trying to measure mass in metres, Crivelli concludes. … But a growing crowd of researchers argues that the variation is so extensive that it stretches the gold-standard idea to the breaking point. Their views are backed up by a vast literature review. A few years ago, the editors of the journal Psychological Science in the Public Interest put together a panel of authors who disagreed with one another and asked them to review the literature.