The feeling of 'disgust' not only helps us to avoid impurities, it may also make people better at detecting them, according to a new study. From an evolutionary standpoint, experiencing the intense, visceral sense of revulsion that comes with disgust presumably helps us to avoid contaminants that can make us sick or even kill us. The new study published in journal Psychological Science found that disgust also allows people to better detect impurities.

If something looks dirty and disgusting, we typically assume it's contaminated in some way; when something is white, however, we are more likely to assume that it's clean and pure, researchers said. Research has shown that people from many different cultures hold this association between lightness and purity, they said. "In the psychology of purity, even the slightest deviation from a pure state (i.e., whiteness) is an unacceptable blemish," said psychological scientist Gary Sherman and co-authors.

They hypothesised that if feeling disgust motivates people to create or protect pure environments, it may also lead them to prioritise the light end of the visual spectrum. For people trying to preserve cleanliness and purity, the ability to distinguish even slight deviations from a light shade like white may become particularly important. Researchers tested participants' ability to make subtle gray-scale discriminations in both ends of the light spectrum. In a study, 123 college students were presented with sets of rectangles. In each set of four rectangles, one rectangle was either slightly darker or slightly lighter than the others.

The participants were asked to indicate which of the four rectangles in each set was different from the other three. After completing the discrimination task, they completed a survey that measured their overall sensitivity to disgust. In general, the students were better at identifying the rectangle that stood out when the rectangles were presented on the dark end of the visual spectrum. People who showed higher sensitivity to disgust also showed better performance on the light end of the spectrum relative to the dark end, the study found.

In two other experiments, researchers found that inducing disgust would actually "tune" participants' visual perception, enhancing their ability to discriminate among small deviations in lightness. The studies provide evidence for an interactive relationship between disgust sensitivity and perceptual sensitivity that may ultimately help people detect and avoid the germs, toxins, and other contaminants around us, researchers said.