The Evolution of Emotion

The Evolution of Emotion

An interesting new theory behind the way human facial expressions developed.


You can tell an awful lot about someone just by looking at his or her eyes—even if the person is a total stranger. How humans are able to so quickly analyze expressions is an ongoing topic of interest for scientists. New research from Cornell University looked specifically at how the eyes developed for sight—but are now also used for insight.

Adam Anderson is a professor of human development at Cornell University’s College of Human Ecology. He and his study co-author, Daniel Lee, created models of six common facial expressions—sadness, disgust, anger, joy, fear and surprise—using faces from databases. Study participants were shown a pair of eyes that described a specific mental state, such as “curious” or “bored,” and were asked to rate how closely it matched the eye expression. They were able to consistently match the metal state to the eye expression, from the eyes alone. Then Anderson analyzed how the perceptions related to what the eyes were doing. For example, how curved was the eyebrow? How open was the eye?

The study showed that people consistently associated narrowed eyes, which enhance our visual discrimination by blocking light and sharpening focus, with emotions related to discrimination, such as disgust and suspicion. On the other hand, open eyes, which expand the field of vision, were associated with emotions related to sensitivity, like fear and awe.

This study continues the research that Anderson had conducted in 2013, which suggests that facial expressions, such as raising an eyebrow, arose from universal, reactions to the environment—like it’s a sunny day out—rather than signaling social communication to other humans. Gradually, we started to attach emotional meaning to these gestures. Darwin had this theory about the evolution of emotion.

“What our work is beginning to unravel,” wrote Anderson, “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.”

Kathryn Drury Wagner is a writer and editor based in Los Angeles. Her latest book is Hawaii’s Strangest, Ickiest, Wildest Book Ever!, a science and natural history “gross out” for young readers.

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