Both objects and behaviour can be described as disgusting. The term could equally apply to someone who cheats other people out of money as it could to the sight of rancid food or the taste of sour milk. That’s not just a linguistic quirk. Some scientists believe that the revulsion we feel towards immoral behaviour isn’t based on our vaunted mental abilities, but on ancient impulses that evolved to put us off toxic or infectious foods.
It seems that your facial muscles agree. Hanah Chapman from the University of Toronto has found that both physical and moral disgust cause the levator labii muscles, which run from your eyes to your mouth, to contract. The result: you wrinkle your nose and you purse your lips. Nasty tastes, gross photos and foul play all cause the same physical reaction and the same subjective emotions. When people say that moral transgressions “leave a bad taste in your mouth”, it’s more than just a pretty metaphor.
Chapman began by studying disgust in its more primitive forms – reactions to foul tastes. She recruited 27 volunteers and recorded the electrical activity in their levator labii muscles as they drank small vials of various liquids. If the concoctions were unpleasantly salty, sour or bitter, this group of muscles contracted more strongly than if the liquids were sweet or flavourless. These reactions were a good measure of their subjective opinions – the more distasteful they found the drinks, the more strongly their muscles contracted.
Throughout our language, the vocabulary of physical cleanliness is also used to describe moral cleanliness. We describe saints as pure and thieves as dirty; consciences can be clean and sins can be washed away. But more and more, psychological studies tell us that these concepts are entwined in a very real way. The act of cleaning, or even just thinking about the concept of cleanliness, can influence a person’s moral compass, swinging it towards a less judgmental direction.
This isn’t the first time that I’ve blogged about this. Two years ago, Chen-Bo Zhong and Katie Liljenquist found that volunteers who dredged up a past misdeed were more likely to think of words related to cleaning or show a physical preference for cleaning products. This “Lady Macbeth effect” is reminiscent of the infamous Shakespearean character and her failed attempts to wash her hands of spilt blood.
Simone Schnall and colleagues from the University of Plymouth have expanded on Zhong and LIllenquist’s study by showing that the effect works in the opposite direction. Not only can feelings of moral muck trigger a desire for physical cleanliness, cleanliness can also change how seriously people view a moral transgression.
They asked 40 volunteers to a rearrange 40 sets of four words into sentences. Through this word-game, they ‘primed’ 20 of the volunteers with thoughts of cleanliness by interspersing half of their sets with cleaning-related words, such as pure, washed, clean, immaculate or pristine. The other 20 volunteers only saw unconnected neutral words in all of their sets.