In times gone by, they used to say the eyes were the gateway to the soul. Science now says they were probably onto something.
A new study published in Psychological Science looked into how humans can communicate and infer emotional states simply by using their eyes. Of course, this is something we all do, sometimes consciously, every day. But this study says it could be even more accurate and deep-rooted than we once thought.
"If you're watching 'Curb Your Enthusiasm' and wonder why when Larry David squints his eyes that conveys scrutiny, our work offers a theory that explains it," author Daniel H. Lee of the University of Colorado Boulder explained in a statement. "Narrowing the eyes for visual scrutiny also communicates scrutiny."
The researchers put 28 participants through 600 trials where they were shown images of eyes that were isolated from people pulling varying expressions, such as sadness, disgust, anger, joy, fear, and surprise. They then had to choose which kind of word describes that person’s mental state.
After looking through the results, the researchers analyzed how these perceptions related to specific eye movements, such as the openness of the eye, the distance from the eyebrow to the eye, the slope and curve of the eyebrows, as well as the wrinkles around the nose, the temple, and below the eye.
Maybe unsurprisingly, the results showed that the participants made fairly similar responses to the expressions. Eye-narrowing was widely associated with mental states related to social discrimination, such as hate, suspicion, and aggression. On the flip side, eye-widening was highly associated with sensitivity, anticipation, cowardice, and interest.
However, these movements were shown to be surprisingly subtle. This could perhaps explain why humans don’t always see eye-to-eye, so to speak.
"Human expressions are highly complex – when enumerating our facial muscles, we computed that there are at least 3.7 x 1016 different expression combinations, which is about the same probabilistic space as two Powerball jackpots," Lee explained. "We looked at a subset of this space – just the eye region – and found that one simple physical dimension (widening vs. narrowing) explained a majority of this complex space in social communication."
The study’s authors say that although these expressions probably originated for practical purposes, they may have been co-opted for social purposes. For example, eye-narrowing might have started in order to gain better visual acuity, perhaps at times of heightened concentration such as hunting or physical confrontation. Hence, it came to be associated with anger and aggression.
"We went back to Darwin," Lee added. "His theories on how expression appearance evolved to have a sensory function for the sender showed how it also co-evolved to have communication function for the receiver."