AV短视频

Malice leaves a nasty smell and causes disgust

Bad attitudes lead to moral judgments rooted in our basic survival mechanisms. And scientists from UNIGE have demonstrated that they are linked to foul smells.

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Part of the human brain contributing the most to the prediction of pain (left, orange areas) and olfactory disgust (right, small blue areas). 漏UNIGE/Corradi-Dell'Aqua.

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Unhealthy behaviours trigger moral judgments that are similar to the basic emotions that contribute to our ability to survive. Two different hypotheses are to be found in the current scientific literature as to the identity of these emotions. Some researchers single out disgust, while others opt for pain. After developing a new approach to brain imaging, a research team from the AV短视频 (UNIGE) has come down on the side of disgust. The study, which can be found in Science Advances, shows that unhealthy behaviours trigger brain responses that are similar to those prompted by bad smells. The research also identifies for the first time a biomarker in the brain for disgust.听

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Disgust is a basic emotion linked to our survivability. Smell provides information about the freshness of foodstuffs, while disgust means we can take action to avoid a potential source of poisoning. Following the same principle, pain helps us cope with any injuries we might suffer by activating our withdrawal reflexes. Psychologists believe that these types of survival reflexes might come into play in response to other people鈥檚 bad behaviour.

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Disgust or pain

鈥淭hese connections have been demonstrated via associations between situations and sensations,鈥� begins Professor Corrado Corradi-Dell鈥橝cqua, a researcher in UNIGE鈥檚 Department of Psychology and the study鈥檚 lead investigator. 鈥淔or instance, if I drink something while reading an article about corruption that affects my moral judgment, I may find that my drink smells bad and tastes vile. Equally, the reverse is true: smells can generate inappropriate moral judgment. In concrete terms, if someone smells bad, other people tend to make the judgment that they鈥檙e unhealthy.鈥澨�

While some studies suggest that disgust is involved in the process, others opt for pain, since they consider that moral judgments are made based on actual facts - hence the parallel with the mechanisms involved in pain. 鈥淚f a driver is distracted, and does not see a pedestrian crossing a road, I will judge this person more negatively if the pedestrian was actually harmed, rather than avoided by chance鈥�, explains the psychologist. His team set up an experimental paradigm and customised magnetic resonance imaging (MRI) techniques in an attempt to decide between the contradictory hypotheses.听

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The train dilemma as a paradigm

The first step was for Corradi-Dell鈥橝cqua鈥檚 laboratory to subject volunteers to unpleasant odours or heat-induced pain. 鈥淭he whole idea was to elicit a similar degree of discomfort with the two techniques so that they could work on the same levels.鈥� Once the calibration had been performed, participants in the study were subjected to readings that evoked value judgments. 鈥淲e used the train dilemma when five people are stuck on a railway track as a train approaches. The only possible way to save them is to push someone off the top of a bridge so that the switch is hit as they fall. In other words, it鈥檚 necessary to kill one person to save five in a highly immoral situation,鈥� explains the researcher. The act of reading this unpleasant dilemma had an influence on the odours the participants smelt and caused disgust, but did not influence the pain, an outcome that was backed up by the participants鈥� electrodermal activity. This is a physiological measurement of the electrical conductance of the skin. It reflects the rate of sweating and the activity of the nervous system responsible for involuntary behaviour.

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Neural pathways identified

Professor Corradi-Dell鈥橝cqua then concentrated on the brain response. 鈥淚t is difficult to infer pain and disgust from neural activity, as these two experiences often recruit the same brain areas. To dissociate them, we had to measure the global neuronal activity via MRI rather than focusing on specific regions,鈥� summarises the researcher. The Geneva team adopted a technique that allows predicting disgust and pain from the overall brain activity, such as specific biomarkers.听

Using this tool, the researchers were able to prove that the overall brain response to disgust was influenced by previous moral judgment. Once again, moral judgments are indeed associated with disgust. 鈥淚n addition to this important discovery for psychology, this study was the occasion for the development of a biomarker prototype for olfactory disgust. It鈥檚 a double step forward!鈥� concludes Corradi-Dell鈥橝cqua.

2020