Are emotional facial expressions such as fear or disgust created by chance? A study published online this week in Nature Neuroscience provides evidence for the suggestion, first made by Charles Darwin, that emotional facial expressions have not evolved randomly, but that they serve to alter sensory experience.

Joshua Susskind and colleagues found that when people pose expressions of fear, they have a subjectively larger range of vision, faster eye movements, and an increase in nasal volume and air velocity during breathing in. While posing fear expressions, people were also able to detect targets which were further away. Expressions of disgust, which are objectively opposite to fear, produced opposite results, with people reporting a subjectively smaller range of vision and a decrease in nasal volume.

These results suggest that fear works to enhance perception of external information, whereas disgust decreases perception.