Next time someone throws you a look, don't take it personally: In a study of fear and disgust (the facial expressions), researchers have shown how those reactions to threat have helped us survive. Scientists studied the effects of eyes widening in fear, admitting more light and broading a participant's field of vision, or narrowing in disgust, focusing more precisely on an object. As two-dozen undergraduate volunteers mimicked each emotion, scientists tracked their vision using using standard eye-exam equipment.
From a recent Los Angeles Times article:
Although some scientists have proposed that emotional expressions are intended primarily to communicate information, study authors argued that expressions of fear and disgust seem to perform different visual functions.
"Eye widening may improve detection and localization of a potential threat that requires enhanced vigilance, which would be consistent with the hypothesized function of fear," wrote senior author Adam Anderson, [PhD,] a professor of human development at Cornell University. (The research was conducted by Anderson and his colleagues at the University of Toronto.)
"Conversely, eye narrowing may improve perceptual discrimination to discern different kinds of threats, such as disease vectors and contaminated foods, avoidance of which is a hypothesized function of disgust," Anderson and his colleagues wrote.
The study was published in the journal Psychological Science.