Why our eyes become wide with fear

Researchers have said revealed the reason behind us becoming saucer-eyed from fear and squint from disgust.

According to a study by a Cornell University neuroscientist, these near-opposite facial expressions are rooted in emotional responses that exploit how our eyes gather and focus light to detect an unknown threat.

Our eyes widen in fear, boosting sensitivity and expanding our field of vision to locate surrounding danger. When repulsed, our eyes narrow, blocking light to sharpen focus and pinpoint the source of our disgust.

The findings by Adam Anderson, professor of human development in Cornell's College of Human Ecology, suggest that human facial expressions arose from universal, adaptive reactions to environmental stimuli and not originally as social communication signals, lending support to Charles Darwin's 19th century theories on the evolution of emotion.

Looks of disgust result in the greatest visual acuity - less light and better focus; fearful expressions induce maximum sensitivity - more light and a broader visual field.

Anderson that these emotions trigger facial expressions that are very far apart structurally, one with eyes wide open and the other with eyes pinched, asserting that the reason for that is to allow the eye to harness the properties of light that are most useful in these situations.

The study has been published in the journal Psychological Science.