When we see behaviors that violate shared moral standards, our brains inhibit the neurons that control our tongue movements – just like it happens when something tastes bad. An international research group led by the Universities of Bologna and Messina reached this astonishing result in their study published in the journal of Social, cognitive and affective neurosciences and recently received the “Best Paper Prize 2021” at the 12th International Neuroethics Conference.

“Our study advances the hypothesis of an oral origin of morality; the drive of rejection originally evoked by oral disgust could have been co-opted to promote the withdrawal of moral transgressions ”, explains Alessio Avenanti who is the research coordinator and neuroscientist at the Department of Psychology at the University of Bologna, Cesena Campus . “Moral disgust is therefore not only a consequence of thought processes and mental cognitive abilities, but is linked to physiological and emotional responses.”

Indeed, “disgusting” describes not only the taste of rotten or inedible food but also an action or behavior that we perceive as revolting because it violates the moral standards of our culture or value system. The researchers analyzed the neurons controlling the motor activity of the tongue to find out if and how this relationship between morality and disgust relies on neuromechanisms related to physical responses.

“From a sensory point of view, the language-disgust link is intuitive, because this oral muscle functions as a sensory organ that encodes flavors through taste receptors located on its surface”, explains Carmelo Vicario, first author of this article. study and professor at the University of Messina. “In a previous study, we had already shown that oral disgust stimuli could inhibit the motor cortex controlling the tongue. This study confirms that a similar process occurs when we witness moral violations ”.

The researchers came to this conclusion using transcranial magnetic stimulation (TMS) on a sample of subjects. TMS is a non-invasive form of brain stimulation that allowed researchers to stimulate the primary motor area of ​​the tongue using an electromagnetic coil positioned on the subject’s head. Study subjects were presented with vignettes of moral transgressions. Neuroscientists then recorded the response of neurons controlling the movement of the tongue through certain electrodes.

They thus showed that the more these moral transgressions indignant the subjects, the more the motor capacity of their language was inhibited. This phenomenon was observed only at the level of the tongue and did not seem to affect other parts of the primary motor cortex.

When we taste something unpleasant, we experience an inhibition of the movement of our tongue. This reaction may reflect an implicit avoidance-defense mechanism to prevent ingestion of potentially harmful substances. This study indicates that a similar avoidance-defense mechanism could have adapted in response to violations of shared moral standards.

“This study suggests neurophysiological evidence linking morality to a physiological response that has implications for the philosophical debate between the moral theories of sentimentalists and rationalists. A debate that increasingly calls for the contribution of philosophers, psychologists and neuroscientists. “, says Giuseppe Pellegrino, who co-authored the study and director of the Center for Studies and Research in Cognitive Neuroscience at the University of Bologna.

The title of the study is “Outrage over Moral Violations Removes Motor Cortex of Tongue: Preliminary Evidence of TMS” and was published in the journal of Social, cognitive and affective neurosciences. The study was coordinated by researchers from the University of Bologna (Alessio Avenanti and Giuseppe di Pellegrino) and the University of Messina (Carmelo Vicario and Chiara Lucifora) and saw the participation of Robert D. Rafal (University of Delaware, USA), Mohammad A Salehinejad and Michael A. Nitsche (Leibniz Research Center on Work Environment and Human Factors, Germany).

In addition, the Italian Society of Neuroethics (SINe) and the International Neuroethics Society (INS) awarded this study the “Best Paper Prize 2021” at the 12th International Scientific Conference on Neuroethics which took place online from May 14 to 21. SINe and INS promote dialogue and encourage multidisciplinary research by emphasizing the social, legal and ethical implications of neurosciences.


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