Disgust is a natural response to unpleasant sights, such as rotting food, bodily waste and creepy crawlies, and has evolved to help us survive, encouraging us to avoid things that might spread disease. But for some people, disgust can become pathological, affecting their mental health and quality of life.
In a study published in Current Biology, researchers at the MRC Cognition and Brain Sciences Unit show that domperidone, a commonly-prescribed anti-nausea medicine, can help significantly reduce how much volunteers look away from disgusting images.
Domperidone works by stabilising the rhythm of the electrical signals in our stomach muscles. Normally, these signals help the stomach expand and contract, helping 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 disrupted – for example, when we feel strong revulsion towards something – they can cause us to throw up the contents of our stomach.
In the study,25 volunteers aged 18-35 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 along with neutral images, such as a scarf or buttons, while the researchers tracked their eye movements. Thirty minutes after taking their tablets, the volunteers were again shown the images while their eye movements were tracked.
Next, the researchers offered an incentive to the volunteers: for every four to eight seconds that they could look at a disgusting image, they would receive 25p – and hear a ‘kerching!’ sound. The volunteers then viewed the images again for a final round, but this time with no incentive.
The volunteers were also asked to rate how disgusting they found the images at the start and end of the trial.
The researchers found that initially, taking domperidone made little difference to the time the volunteers spent looking at a particular image. As could be expected among both groups, the dwell time increased dramatically when they were paid to look at the images.
Image: An expression of disgust
Credit: Wellcome Images
Reproduced courtesy of the University of Cambridge