The Influence of Disgust on Morality

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoy this article, please consider a print or digital subscription!)

Dan M. Kahan describes two court cases in his article, “The Anatomy of Disgust in Criminal Law,” for the Faculty Scholarship Series of Yale Law School. In one of them, defendant Stephen Roy Carr claims to have murdered a lesbian couple out of pure disgust after having observed them in a sexual act. The judge, insisting that disgust had nothing to do with murder, upped the sentencing to voluntary manslaughter. In the other, Richard Lee Bernardski killed two gay men after having accepted a ride from them to a remote spot. His motive? Gay men repulsed him. That judge, however, empathized with the defendant’s “revulsion” and softened his sentence. These cases, though similar, yielded quite different results.

Morality is thought to rely on emotions, and disgust is one of them. In a legal system where guilt is not only determined by the existence of hard evidence but also by one’s intention to do harm, emotional persuasion weighs heavily on all parties. In court, moral decisions abound from the moment a criminal decides to commit a crime to the moment a judge determines his fate.

Essentially, a moral sense is a code of values that guides someone’s actions in a social context. For example, we all know the Golden Rule: “Do unto others as you would have them do unto you.” Although it appears to be socially constructed, some believe humans evolved with an innate moral sense to help them survive in a world that thrives on mutual cooperation. Disgust, however, is thought of as one of the “basic emotions.” That is, disgust is believed to be distinct, continuous across species, hard-wired in the brain and evolutionarily functional. In research, scientists sometimes lump disgust into one broad category, but some note two types.

Physical disgust, say, in response to a rotting corpse, is thought to help humans avoid disease; interestingly, judgments ease up when you reverse it with cleanliness. Social disgust, for instance, about incest, is thought to help humans dodge dangerous social situations. Disgust, as we’ve seen, has been shown to influence moral judgments. People make harsher judgments when a moral dilemma is associated with higher levels of disgust.

As technology advances, so does scientific insight into the neural underpinnings of disgust and morality. Although likely to develop its own branch of cognitive neuroscience within the next few years, the neurobiology of morality is complex and convoluted with philosophical debate. To ever truly understand it would be a massive feat. To get past this point, scientists break morality down into digestible chunks with testable hypotheses. For example, scientists have recently been chewing on how to determine if a feeling of disgust is necessary to judge whether an act is right or wrong.

In one study, they examined temporal differences with electroencephalography (EEG) and recorded neural responses on the human scalp to moral and disgusting stimuli. Cue the electrodes. In a task, subjects are asked to push a button with the left or right hand to indicate the morality of an act, but only if they feel the act is also disgusting. If the act is not disgusting, the subjects are to do nothing. This is called a “go, no-go” task. For example, a subject may have to determine the morality of a statement such as “A person at a party is drinking blood.” However, the subject will only press the button if he or she finds it disgusting. By varying stimulus delivery, researchers parsed out which stimulus the brain processed first. And guess what? It turned out to be the moral one. It appeared that people were not rationalizing moral judgments via emotion, at least where language was concerned. They seemed to follow moral intuition.

The information gained from studies like this one has important legal implications, but deciding what to do with them won’t be an easy task. Consider the crimes above. Does knowing whether the defendants were impacted by their disgust make these heinous acts any more tolerable?

(Editor’s note: This article is from a past issue of Brain World magazine. If you enjoy this article, please consider a print or digital subscription!)

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