Disgusting, isn't it?

Disgust is a universal emotion among human beings, but can it be used as a guide to moral decisions? According to so-called “bioethicist” Leon Kass (University of Chicago, chair of Prez Bush's Council on Bioethics from '02 to '05) the answer is a resounding yes:

“We are repelled by the prospect of cloning human beings not because of the strangeness or novelty of the undertaking, but because we intuit and feel, immediately and without argument, the violation of things that we rightfully hold dear… Shallow are the souls that have forgotten how to shudder.”

“Immediately and without argument”? Hmm, let's see, I have an instinctive reaction of disgust – immediate and without argument – to cockroaches (not to mention to pompous bioethicists), and yet I do not advocate their eradication from planet earth, perhaps mindful of something my grandmother used to say (in Neapolitan dialect): “Ogni scarrafone e` bello a' mamma soja” (roughly, every cockroach is beautiful to his own mother).

The quote by Kass is used as the entry point for an insightful essay on disgust published recently in Nature by Dan Jones (14 June 2007). Jones goes on to show that recent research on disgust implies that Kass's “reasoning” is deeply flawed: there are plenty of things we find instinctively distasteful, but it turns out that instinct is often a bad guide to decision making, especially of the moral kind.

Jones traces the roots of disgust for morally repugnant actions to its more biologically basic counterpart: disgust to things that may injure us physically. For example, disgust at the sight of blood and feces probably originated because it is in fact good to confine the first one inside our bodies, and keep the latter as far as possible from us.

Brain imaging studies have shown that there is an overlap between the neural basis of “core” and “cognitive” disgust, i.e. of disgust for biological objects and for morally repulsive actions respectively. As is usual in evolution, old tools (neural machinery for core disgust) are reused and reshaped for another function (cognitive disgust).

While the rest of Jones' essay is fascinating, I want to draw attention to a particular finding that sheds some additional light on that perennial difference between socially progressive and conservative people, a distinction that has existed since the dawn of recorded history, and that is causing so much havoc still today. University of Virginia psychologist Jonathan Haidt and graduate student Jesse Graham have expanded on previous theory to come up with a list of five domains for ethical “intuitions” that seem to be common across humankind: concern for harm to people, fairness, loyalty to members of the in-group, respect for authority, and “spiritual” purity.

Haidt and Graham then asked 1,613 people who identified themselves as liberals or conservatives to answer questions aimed at identifying which of the five domains elicited strong reactions from them (including cognitive disgust at certain possible moral scenarios). The results were stunning, if not entirely surprising with hindsight: while conservatives where sensitive to all five moral “domains,” liberals were concerned only with the first two (harm to others and fairness).

That may go a long way toward explaining why certain people simply cannot see the point of starting a moral crusade in response to, say, homosexuality (which falls under “spiritual purity,” whatever that is), or do not understand how someone can follow a leader regardless of how stupid or criminal his actions may be (“my country right or wrong,” which falls under both respect for authority and loyalty to the in-group).

Now, a conservative could argue that liberals are morally stunted, that they only “see” (and, more importantly, feel strongly) about a sub-set of the ethical domain. But another possibility is that conservatives don't realize that evolution is tricking them, that they are simply mis-applying their cognitive disgust to improper domains, just like Kass' pathetic appeal to conclusions that are “immediate and without argument.” Wanna bet on which of these two explanations I favor?