Bad deeds have an odor

By morally condemning the actions of others, we activate our own brain centers of disgust.

"This is disgusting," people say when they mean something unacceptable, unethical, immoral. And they really start to feel disgust: scientists have discovered that any unacceptable actions of other people cause a literal feeling of disgust in the human brain, similar to that which occurs when feeling foul odors. This was reported by specialists representing the University of Geneva: they decided to find out how the brain reacts to bad actions - painfully or with disgust.

At the beginning of the experiment, the participants were given an unpleasant aroma, then a slight pain from a light burn. In this way, the scientists were able to understand the specifics of a particular person's reaction to unpleasant physical sensations. After that, the participants were asked to read the famous "trolley problem": the essence of its description is the ability to sacrifice one person in order to save several people. This dilemma usually causes many opinions. On the one hand, it is wrong to say that one person has less value than, for example, five or six people. However, leaving one and losing several victims is also immoral, so choosing the right answer is very difficult, and is there one?

The study showed that after being exposed to the dilemma, participants showed increased sensitivity to unpleasant odors, with relative stability of pain sensitivity. Similar results were observed in the brain activity, which was assessed using a functional type of magnetic resonance imaging. As scientists explain, the sensation of pain and the feeling of olfactory disgust stimulate similar brain areas, which are quite difficult to isolate separately for MRI. However, specialists were able to do this and, based on brain activity indicators, they found that moral condemnation intensified the feeling of disgust. Therefore, it can be safely said that bad deeds smell bad, but are not physically painful. However, it should be clarified that we are not talking about a clear smell: this is rather a metaphor, because there are always several smells around a person at the same time, and not all of them are pleasant. However, we begin to feel an unwanted aroma much more acutely after falling into moral indignation.

The emergence of a relationship between disgust and condemnation of the moral side of the issue is traced using the theory of evolution. A bad smell, along with disgust, signals some kind of danger, possible harm. Something smelling bad can be poisonous, spoiled, infectious, initially unacceptable. And as socialization developed, generally accepted moral criteria were formed.

Those who dare to violate the general criteria of morality put the entire social group at risk, which provokes condemnation. The brain does not restructure or transform, but uses a long-existing neural response - like olfactory disgust.

The scientists' work is presented at www.advances.sciencemag.org