There are 43 muscles in the human face, so it's no wonder that the range of emotions expressed by those muscles extends well beyond the six reseachers tend to focus on—"happy sad, fearful, angry, surprised and disgusted," according to the Guardian. And now researchers have identified 21 "emotional states" and their corresponding human facial expressions.
Researchers used a computer program to analyze the faces of 230 volunteers. These 21 expressions, the researchers found, were more or less universal among the group, NPR reports. Some were hybrids of basic emotional states, like happily disgusted (i.e., when you watch The Aristrocrats) or sadly angry (i.e., when you discover your signficant other is cheating on you).
The volunteers were all American, NPR points out, so at this point the team doesn't know whether or not happily disgusted is a distinctly North American expression or a universal human experience.