The Key to Reading Facial Expressions
We know from experience—and cartoons—that we open our eyes wide when we see something that surprises or excites us, and squint when we're wary.
New research suggests that more than any other part of the face we look to people's eyes to tell us what they're thinking and feeling. Scientists from Cornell University and the University of Colorado, Boulder asked people to identify the emotions of others based only on photos of their eyes and one of 50 words describing a mental state (like "discriminating," "curious" or "bored").
Given only a photo of eyes and a single word, participants were able to correctly identify all six basic emotions the researchers were testing for—sadness, disgust, anger, joy, fear and surprise. For example, they consistently linked narrowed eyes with emotions related to discrimination, like disgust and suspicion. They associated open eyes with emotions related to sensitivity, such as fear and awe.
The researchers analyzed the images to figure out what exactly about our eyes helps other people figure out what we're feeling. They considered the distance from the eyebrow to the eye, the slope and curve of the eyebrow and the wrinkles around the nose, temple and below the eye. But they found that the openness of the eye is the tell—it's most closely related to humans' ability to read emotions from the eyes.
They compared participants' ability to read eyes to their ability to discern emotions from the mouth and even the nose. According to their results, the eyes offer more insight into someone's true emotions than other parts of the face. Maybe that's why it's pretty easy to tell when someone's faking a smile.
The evolutionary science behind side-eye
Despite the help others' eyeballs give us in understanding their emotions and navigating social situations, eye expressions weren't developed for that purpose, said Adam Anderson, Cornell human development professor and author of the study.
"The eyes evolved over 500 million years ago for the purposes of sight but now are essential for interpersonal insight," Anderson said to Cornell.
Our facial expressions developed for survival reasons, the researchers found in a previous study. Humans originally made different faces purely to adapt to our environments, not to communicate with one another. For example, squinting, which now might signal suspicion to others, blocks light and sharpens your eyes' focus, making it easier to suss out a sketchy situation. Widening your eyes communicates amazement or fear but also expands your field of vision, allowing you to take in more. Over time, these simple adaptations became crucial to our nonverbal communication.
“What our work is beginning to unravel are the details of what Darwin theorized: Why certain expressions look the way they do, how that helps the person perceive the world, and how others use those expressions to read our innermost emotions and intentions," Anderson said.