Disgust is a natural response to unpleasant sights, like rotten food
Researchers at the University of Cambridge, UK, explain what lies behind the phrase “my stomach turns” when something disgusting is seen. According to the study, changes in the rhythm of our stomach lead us to look away from disgusting images.
Disgust is a natural response to unpleasant sights like rotten food, bodily waste, and weirdos, and it has evolved to help us survive, encouraging us to avoid things that could spread disease. But for some people, disgust can turn pathological and affect their mental health and quality of life.
In a study published Tuesday in the journal Current Biology, researchers from the Cognition and Brain Sciences Unit is a branch of the UK Medical Research Council show that domperidone, a commonly prescribed anti-nausea drug, can help to significantly reduce the number of volunteers looking at unpleasant images.
The domperidone acts to stabilize the rate of the electrical signals in the muscles of the stomach. Normally, these signals help the stomach expand and contract, helping to move food through the digestive tract. These rhythms become abnormal when we are nauseous or when we are hungry or full, for example. When they are strongly interrupted, for example, when we feel a strong repulsion towards something, they can cause us to vomit the contents of our stomach.
In the study, 25 volunteers between the ages of 18 and 35 were randomly assigned to one of two groups: one group to receive domperidone, the second a placebo.
Before taking their pills, the volunteers were shown a series of unpleasant images alongside neutral images, such as a scarf or buttons, while the researchers followed their eye movements. Thirty minutes after taking their tablets, the volunteers were shown the images again while their eye movements were tracked.
The researchers then offered an incentive to the volunteers: For every four to eight seconds they could look at an unpleasant image, they would receive 25 pence and hear a sound. The volunteers saw the images again for a final round, but this time without any incentive.
The volunteers were also asked to rate how disgusting they found the images at the beginning and end of the test.
The researchers found that initially, taking domperidone made little difference in the time volunteers spent looking at a particular image. As was to be expected between both groups, the dwell time increased dramatically when they were paid to look at the images.
In the final condition, when the volunteers were no longer incentivized, the team found that the volunteers who had received domperidone spent much more time than the placebo group looking at the disgusting images. In the end, people looked at the neutral image about 5.5 seconds longer than the disgusting image, but under the influence of domperidone, the difference was only 2.5 seconds. Domperidone did not influence how unpleasant the images were rated by the volunteers.
“We’ve known for some time that when you see something unpleasant, the electrical signals from the stomach muscles go out of regulation, which in some cases makes people feel sick or the stomach churns. So you’re likely to avoid that thing,” says Dr. Camilla Nord, from the MRC Brain Sciences and Cognition Unit at the University of Cambridge.
“What we have shown here is that when we stabilize the electrical signals of the stomach, people avoid an unpleasant image less after interacting with it,” he continues. “Changes in the rhythm of the stomach led to a reduction in the avoidance of displeasure in our study, so the rhythm of the stomach must be one of the causes of the avoidance of disgust in general. “
“In another recent study, we showed that we do not become immune to looking at disgusting images, a fact supported by the placebo status in this new study,” adds Dr. Edwin Dalmaijer, also from the MRC Unit. This is one of the reasons why those where the treatment of pathological disgust through exposure is often unsuccessful. Our research suggests that domperidone may help. “
“We have shown that by calming the rhythm of the stomach muscles with anti-nausea medications, we can help reduce our instinct to look away from a disgusting image,” explains Professor Tim Dalgleish, also from the MRC Unit, “but simply Using the drug itself is not enough: overcoming disgust avoidance requires that we be motivated or incentivized. This could provide us with clues as to how we can help people clinically overcome pathological disgust, which occurs in a number of mental health conditions and it can be disabling. “