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Robert Kurzban

The Evolutionary Psychology Blog

By Robert Kurzban

Robert Kurzban is an Associate Professor at the University of Pennsylvania and author of Why Everyone (Else) Is A Hypocrite. Follow him on Twitter: @rkurzban

Disgust and Morality, The Sequel

Published 10 December, 2012

My prior post on the relationship elicited a set of comments giving readers’ own views of the relationship between morality and disgust. In this post, I thought I’d indicate my reactions, and then give my position, which can be found in somewhat greater detail in a paper I was fortunate to work on with Josh Tybur, Deb Lieberman, and Peter DeScioli, now available (pay wall) online from Psychological Review.

First, to recap, in the prior post I suggested that there are really two distinct questions about the relationship between disgust and morality, which can be briefly glossed as:

  • Why are disgusting things moralized?
  • Why are immoral things called “disgusting?”

One reader, Lee Kirkpatrick, suggested what I’ll call the Diagnostic argument. He proposed that a person who performs the disgusting acts in question “deserves to be condemned and punished not so much for committing the disgusting act per se, but because committing that act is (believed to be) diagnostic of other more nefarious activities.”

It seems to me that Lee is right that one can make some sort of probabilistic inferences about people who engage in various disgusting activities. Things that people find disgusting tend to be, simplifying, fitness errors: having sex with the wrong sorts of entities (e.g., chickens) or exposing oneself to harmful pathogens. So, I agree that an inference is licensed along the lines of: people who perform disgusting acts might deviate in some important respect from the species-typical design. In turn, people who deviate from the species-typical design are unpredictable and therefore more dangerous than the average bear. To me, this argument – the Diagnostic argument – explains why I might avoid such people, in terms of choosing them as friends or allies, and perhaps even in terms of physical proximity. That is, the Diagnostic argument affords, well, a diagnosis, but it doesn’t seem to me that the cure is moral censure, but rather avoidance. When acts are moralized, by and large, it means that people in the group impose costs of some sort on the individual committing the acts in question, and it’s less clear to me that I benefit from having costs imposed on such people, whether by me or by others. The Diagnostic argument is at its heart an informational argument: I have learned something about a person who commits disgusting acts. The right reaction to this new information, it seems to me, is keeping one’s distance, which is why I’m not a big fan of this explanation.

Lee’s response to my argument along these lines echoes Larry Fiddick’s take on this issue. Larry makes what I’ll call a Negative Externalities argument, suggesting that disgusting acts are moralized “because they can potentially harm you (or your kin).” One example he used is that if you eat a part of a SARS-infected cat, then I might get SARS from you, which of course means that I’m better off in a world in which no one eats SARS-infected cats. A rule that specifies punishing any cat-eating at all accomplishes this by disincetivizing the activity. That is, supporting the moralization of this behavior is simply following one’s self-interest. By supporting punishment for all cat-eating, I’m using morality to make myself better off by reducing probabilistic harm in the form of parasite transmission through SARS-infected-cat-eating.

I’m sympathetic to this argument in general, but my worry about this lies in the particulars. The SARS case and another example Larry uses, homosexuality, both strike me as uncommon or oblique pathways from disgusting acts to harm, and other moralized acts strike me as even more difficult to spin as having externalities, such as masturbation or feces-eating. So the Negative Externalities seems to require indirect and low probability routes from the acts of others to harm to me. Further, it seems to me that negative externalities are everywhere, including many that attach to  non-disgusting behaviors and, further, we moralize lots of things that have positive, rather than negative effects, such as, historically, the charging of interest and, still, the sale of kidneys and livers.

Still, I am sympathetic to this general line of argument. As Lee points out, I and my colleagues have proposed that opposition to recreational drug use might be explained in this way. But in such cases our argument is slightly different, having to do with strategic interactions as opposed to externalities. We assume that some moral regimes are better for some people than for others. So, for instance, if I am an individual for whom infidelity is a big potential cost – because I’m an investing monogamous mating strategist as opposed to a mating-effort specialist – then I benefit from regimes that penalize, and so disincentivize, infidelity. This can be thought of as using the punishment institutions in my local social group to inhibit the classes of behavior that probabilistically harm me. So, suppose that people believe that recreational drug use leads to increases in promiscuous sexuality. Because high-investment men are better off in a world in which there is less extra-pair sex, moral regimes that moralize sexuality – or acts that facilitate sexual behavior, such as recreational drug use – constitute a strategic win for such men. This, we have argued, explains why some people, but not everyone, moralizes this behavior.

So what do I think about the answer to the first question? I prefer an epidemiological sort of argument. Moral contents vary greatly across different places and times. This variation suggests that moral contents are socially transmitted, and, further, that moral contents change over time, likely as a result of support for or resistance to various moral contents and regimes in a given social group. (A modern example is homosexuality, which has become steadily de-moralized over time.) Because, as indicated above, different moral regimes help or hurt different people, there might be systems designed to evaluate whether a particular candidate moral rule is likely to help, hurt, or have no effect on one’s interests. From a strategic perspective, one might expect individuals to resist rules that make them worse off, but endorse rules that make them better off, or, importantly, were neutral with respect to their own interests.

One sort of moral rule that people might not be expected to put up much resistance to supporting is one that specifies behaviors that one doesn’t want to do anyway. Acts that elicit disgust are, generally, the sorts of things that most people don’t want to do – indeed, the emotion is designed to steer them away from such acts – giving rules about disgusting acts an epidemiological advantage. So, the proposal in the Tybur et al. paper is that disgust serves as an input to systems that judge the strategic impact of a given candidate rule. To the extent that an act elicits disgust – meaning that I don’t want to engage in the act in the first place – I ought to be (in the fitness sense) in favor of, or at least not opposed to, moralizing the act. This sort of account might help to explain why, for instance, it seems to take so long to de-moralize disgusting acts.

That’s my view on the first question. Just to finish up, in my prior post, Giner-Sorolla refers to an ‘in press’ paper in Psychological Bulletin which he says suggests that “‘disgust’ felt at non-bodily moral violation is a linguistic or metaphorical slippage from the use in English.” I haven’t read the paper in question, so I can’t say much about this, but this seems like a reasonable answer to the second of the two questions, above, why we use the language of disgust to refer to non-sexual, non-pathogen morally wrong behaviors, such as stealing from orphans. We make a related argument in the paper I mentioned at the top of this post.

  • http://gnoughts.blogspot.com/ Vlad The Impatient

    Wouldn’t a defence of the Diagnostic Argument be that moralising such stuff is in fact just a social shorthand/shortcut? So nobody needs analyse (even sub/unconsciously) the behaviour on a case by case basis, but is culturally primed against some sorts of behaviours that in the past have been found to be “bad”? So it does start as avoidance, but the culture eventually moralises it into something you can teach your kids, sort of thing – which moral rules tend to be, at least IMHO?

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