Human Faces Might Only Express Four Basic Emotions

How many facial expressions can you make? Offhand, you might guess ten, or twenty, from fear to disgust to sadness to joy to skepticism. But researchers now say that human faces might only be able to make four universally recognized facial expressions.

For a while, researchers thought that there were six faces that everybody in the world could identify: happiness, sadness, fear, anger, surprise and disgust. Now, a new study out of the University of Glasgow suggests that some of those share facial “signals” and should be combined. They argue that fear and disgust share the same key facial signal: the wrinkled nose. The same goes for fear and surprise, both involve widened eyes and should be combined.

There are 42 individual facial muscles in the face. To examine how each of these muscles impacts facial expressions, the researchers worked with people who are specially trained to be able to activate each and every one of those 42 muscles. (Apparently those people exist.) Scientists filmed these super facers activating these muscles individually, and then built a computer model in which they could pick and chose which muscles a digital face flexed. They then asked volunteers to look at this model as it made faces, and identify what expression they were seeing.

This was when the anger/disgust and fear/surprise signals got crossed. When the basic units of each expression were made with just a few muscles, people couldn’t tell them apart. It wasn’t until more and more facial muscles were activated that people could distinguish between the faces. Rachel Jack, the lead researcher on the project, told the University’s press office, “What our research shows is that not all facial muscles appear simultaneously during facial expressions, but rather develop over time.” In other words, when you’re about to make a mad face, you start with a few muscles, and activate more and more over time to finish the expression. It isn’t until you’ve got most of those muscles flexed that someone else can tell you’re mad, and not grossed out.

According to the university, Jack intends to test her facial expression model in other countries to see if the same things happen:

The researchers intend to develop their study by looking at facial expressions of different cultures, including East Asian populations whom they have already ascertained interpret some of the six classical emotions differently – placing more emphasis on eye signals than mouth movements compared to Westerners.

In the meantime, it might be worth learning how to activate all your face muscles individually to avoid confusion. 

Rose Eveleth | | READ MORE

Rose Eveleth was a writer for Smart News and a producer/designer/ science writer/ animator based in Brooklyn. Her work has appeared in the New York Times, Scientific American, Story Collider, TED-Ed and OnEarth.