There Once Was a Man Who Could Not Feel Disgust

November's Nature Neuroscience reports the case of a British fellow with a brain injury who had lost the ability to feel disgust.

Neuroscientists at the MRC Cognition and Brain Sciences Unit, in Cambridge, presented the 25-year-old stroke victim with pictures of disgusting things, and other stimuli don't bear describing in detail. They also showed him pictures of people's faces registering disgust. The man reported drastically attenuated personal reactions to disgust-provoking situations. Likewise, although he retained the ability to identify a variety of facial expressions, he was unable to recognize the expression of disgust in other people.

How remarkable that an emotion like disgust — try explaining it! — owes its existence, apparently, to a couple of loci in the insula and putamen.

Are there any human emotions or intellectual functions that are irreducible to biological functions? Descartes struggled with this problem but got sidetracked.

In the health professions, there is a substantial body of literature and a broad general awareness addressing the adjustment from a lay person's sensitivity to a professional's. Some students experience this transformation as a loss, but at the same time it is unquestionably a gain. The ability to overcome disgust is an indispensable skill for all who care for the sick or wretched of the earth. Imagine how ineffective Mother Theresa might have been if she had been unable to rise above this inconvenient emotion.

Does desensitization equal objectivity? Does it make us stronger or weaker? Does the reflex of wrinkling our nose reflect well, or ill, on us? Take the example of the English patient above. Is he — all other things equal — a better humanitarian now? Or does he deserve sympathy, like one who has lost the use of an eye or an ear? Most likely, "it depends."

Endless illustrations

Of course, there must be some people born without the disgust organ. I believe it is a cardinal law of embryology that, if a function can be localized to a specific anatomic part, there must exist individuals in which that part failed to develop. There are endless illustrations. We have all met people without musical talent, color vision, good taste, charitable dispositions, honesty, loyalty, or courage.

Some occupations seem to attract people with a characteristic spectrum of sensitivities. I suspect prisons house thousands of people who are disabled in one or another capacity that society considers essential to good citizenship. Then, how should we classify those without the ability to feel disgust?

Maybe we should be a little jealous? But we might also be sorry. Here is another instance of a potentially advantageous, but limiting, "mutation." Knowing nothing about the case, we might imagine the English patient to be especially suited to certain jobs that the more squeamish would be incapable of performing. Does that suggest we should steer him in those directions? Is this fair?

To heighten the contrast, we have all dealt with people who are hypersensitive. How annoying they are, with their sniveling and blustering and indignation. In daily commerce we find it much easier to deal with placid, tolerant, and patient individuals, who never become outraged or exasperated. Whichever side of the service counter we happen to be on, we all benefit from anesthetizing those little parts of the insula and putamen that bring inconvenient passions to our transactions. In many social contexts, sensibility is a handicap.

Would it be fair to ask those with an unusually hyperactive disgust organ to work side by side with the English patient? I suppose there is a certain range of sensitivity that we consider "functional," outside of which we label people, "impaired." Speaking from somewhere in the middle, I have to admit an inexplicable pride in my ability to feel disgust, and I admit now a little pride in this capability, which I had neglected to appreciate before. Perhaps I shall cultivate it.

Of course, there's the perverse side.

Imagine the commercial value this serendipitous case might have to British pharmaceutical and biomedical engineers. Conceivably, they could develop a drug specifically targeting and blocking the disgust reaction. Or a little electrode might be implanted that could selectively stun the brain's disgust centers. Maybe through simple biofeedback we could all be taught to placate the locus disgustus at will.

Useful reaction

I can think of a thousand uses for a selective blocking agent for disgust. Television programs, political campaigns, and a great deal of contemporary art would all be much easier to view under the influence of a slow-release, antidisgust patch. I would slap on a patch before reading the newspaper every morning. Candidates for public office could hand it out like breath mints. There's huge potential here.

Yet, what kind of society would we have, without disgust? For one thing, I wouldn't go out to eat much. I want that guy at the hamburger stand to have a sense of disgust at least as refined as my own. Likewise, I would ask public health inspectors to undergo special training classes in disgust. In this light, disgust could actually be one of the pillars on which civilization is based. After all, pigs never developed a written language, and it's probably just as well.

I can see the Society for Experimental Poetry applying for a grant to study this unfortunate English patient. It would surely wish to measure his capacity for pity, shame, and indignation — and concoct theories about how these are related.

All these are reasons why I scoff at those who enumerate merely six senses. (Five, for those who haven't seen the recent movie.) It's clear to me that the number of human senses is legion. As with other intellectual gifts, we all display more or less aptitude in each of them. The ability to do math homework, to give a good back rub, to know when one is acting like an idiot — these are some of the countless talents humans may have in greater or less measure.

So, to the guy who has lost his disgust, I say, "Use this gift for the betterment of yourself and those around you."

Michael S. Victoroff, M.D., is medical director for Aetna U.S. Healthcare of Colorado. He had practiced family medicine for 19 years.The author's opinions do not necessarily represent opinions or policies of Aetna U.S. Healthcare, its management, or its employees.

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