Why do we wrinkle our noses in disgust or widen our eyes with fear? A new study shows that doing so might help keep us alive.
The idea that facial expressions confer a survival advantage was first posited, perhaps not surprisingly, by Charles Darwin. In 1872, 13 years after he published On the Origin of Species, Darwin wrote a lesser-known tome, The Expression of the Emotions in Man and Animals. In it, he observed that some human expressions occur across cultures and even in some other animals. He cited the wide-eyed gasp of surprise as an example. Darwin speculated that these emotional faces might serve a biological function, such as getting a good look at an enemy.
Darwin's hypothesis went untested until 3 years ago, when cognitive neuroscientist Adam Anderson, graduate student Joshua Susskind, and their colleagues at the University of Toronto in Canada decided to apply new technology to the century-old idea. The researchers computer-generated a "classic" fear face: one with raised brows, popping eyes and flaring nostrils. They also mocked up a disgust face: the wrinkled nose, raised lip, and narrowed eyes familiar to anyone who's smelled rotten eggs or stepped in something foul. The team then asked volunteers to mimic these faces while taking vision and breathing tests.
Emotional faces weren't just for looks. The team found that a fearful visage improves peripheral vision, speeds up eye movement, and boosts air flow, potentially allowing a person to more quickly sense and respond to danger. Squinty, scrunched-up disgusted faces had the opposite effect, limiting vision and decreasing air flow, ostensibly to keep out substances that might be harmful to the eyes or lungs.
The findings, reported online this week in Nature Neuroscience, are "pretty radical," says Anderson, because most research on expressions has focused on their function in communication, not their physiological or evolutionary underpinnings. "No one's ever shown this in a scientific way," adds neuroscientist Elizabeth Phelps of New York University in New York City. "The best kind of study seems obvious on the one hand, but no one's demonstrated it before," says Kevin Ochsner, a cognitive neuroscientist at Columbia University. "This is one of those studies."