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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 & Morality

Published 27 November, 2012

Paul Bloom and David Pizarro recently did a bloggingheads conversation about the link between disgust and morality. I watched most of it, and I thought it was interesting, likely worth a listen to people interested in either or both of these topics. As something of an aside, there’s an interesting moment (43:37) in which Pizarro talks about how evolutionary psychologists have been “fighting the good fight” in terms of “going way out of their way” when talking about political hot topics such as rape in emphasizing that discussing rape or studying is not the same as condoning it. Pizarro says that “we” – by which he means, I think, social psychologists – should try to emulate evolutionary psychologists in this respect.

So, that’s interesting, but not really closely related to the main question, which is why there is a strong relationship between morality and disgust. In fact, as Josh Tybur, Deb Lieberman, Peter DeScioli and I argue in a forthcoming paper, there are really two issues that might be teased apart, but it seems to me are often sort of mixed together.

The first issue is perhaps the more obvious one, which is that lots of disgusting things are moralized. That is, in various places and at various times, lots of acts that evoke the emotion of disgust are seen by a community as “wrong,” meaning that if someone is found to have committed the act, they are subject to punishment by whatever means the society in question uses.

Which acts evoke the emotion of disgust? Well, two important sorts of stimuli seem to do it. The first is cues to the presence of potentially harmful pathogens, such as dead and decaying plants and animals. Disgust seems to be well designed to take pathogen-related cues as input, motivating appropriate defense, typically keeping one’s distance. The second sort might be glossed as sexual activities with partners that represent fitness losses: Sex with one’s close genetic relatives, for instance, because of the well-known potential costs of inbreeding.

It is easy to imagine a world in which people find these sorts of things disgusting but not immoral. Indeed, Pizarro discusses this briefly, alluding to how he might find nose-picking disgusting, but not worthy of punishment. From this is seems clear that not all disgusting things are moralized. Yet, many disgusting acts are frequently moralized, though the examples that come to mind easiest are probably in the context of sexuality, such as incest and, the perennially favorite example, having sex with a chicken (see image, below).

Disgusting? Immoral? Both?

On the surface, moralizing disgusting acts seems somewhat puzzling for a few reasons, though how puzzling you find this might depend on your theory of the function of morality. First of all, if you think that morality has something to do with the prevention of people doing things that are good for them but bad for others, then it seems perverse to find disgusting acts immoral. After all, disgusting things are the sorts of acts that people by and large don’t want to do in the first place. If morality is for constraining others’ behavior, then why “constrain” people to avoid the very things we all tend to avoid anyway?

Second, and related to the question of why constrain people from doing things they don’t want to do, why constrain people from doing things that don’t hurt others? If, again, your theory of morality has something to do with bringing about benefits, then why are disgusting things, which by and large only hurt the actor (or an unfortunate chicken) moralized? (If you don’t like the chicken example, masturbation – which has not infrequently been moralized – also fits here because no one — and no other entity — is involved.) Third, a perennial question is why people want to prevent others from acts that might even help the moralizers, with homosexuality being the typical example. From the standpoint of a man competing for mates in a society, obligate homosexuality would seem to be a benefit, not a cost, insofar as it diminishes competition.

So, why disgusting acts are so often moralized seems to be mysterious. This is not to say that some haven’t offered possible explanations, most notably perhaps my University of Pennsylvania colleague Paul Rozin, and, more recently, Jon Haidt, who has written extensively on the subject, focusing attention in particular on the idea that morality binds people together in groups.

There is a second link between morality and disgust. Many acts that are not disgusting in either the pathogen sense or the sexual sense are labeled as “disgusting.” So, even though there is no disease or sex involved, one might say, “Fred’s stealing $100 from the Widows and Orphans fund was disgusting.” Such linguistic forays are made with enthusiastic frequency. As I was writing this, I Google-Newsed (?) “disgusting” and found the non-payment of wages to employees – a moral violation: in this case, a contract breach – thusly: “To treat staff this way in one of the wealthiest countries in the world, regardless of the circumstances surrounding their place of work, is disgusting.” I also found that Anthony Hopkins referred to “Oscar groveling” as disgusting, and this from a man who played a guy who ate other people’s faces. (I quite recommend Google-Newsing “disgusting” and looking at the acts so categorized. It feels slightly voyeuristic, but has redeeming scholarly virtue.)

So, two questions. Why are disgusting acts moralized, and why are (non-literally-grossing-out) morally wrong acts labeled “disgusting?”

I hope you enjoy the bloggingheads.


  • discoveredjoys

    Johnathan Haidt argues that individuals experience a social dimension of Sacred/Profane or Pure/Polluted. I’d go further and argue that there is a general metaphor of ‘up is good’ and ‘down is bad’ which we use to think by, and it is this metaphor which links sacred/pure/wholesome/elevated, and also links profane/polluted/diseased/degraded.

    Arguably this basic metaphor, held by individuals, underpins ‘up is good’ and ‘down is bad’ attitudes held collectively. The collective metaphors become ‘morals’, i.e. instances of the up/down metaphor held by the General Other.

    Once the socialised metaphor has become established other behaviours (which don’t involve blood, urine, faeces, dead bodies etc.) can also become attached to the disgust dimension. – as long as the metaphor works.

  • Lee_Kirkpatrick

    Given that you’re taken an unorthodox approach in this post by offering questions rather than answers, I’m going to take an unorthodox approach in my response: Rather than telling you what I think the answer is, I’m going to tell you what I think YOU think the answer is, and you can tell me if I’m right. Here I’ll focus on the first question, which I agree needs to be treated separately from the second.

    First, I think you think that the apparent morality-disgust connection is actually a much bigger puzzle than most people realize, because disgust seems to work in precisely the way that (you think) morality doesn’t. Fundamentally, disgust is a self-regulatory system designed to guide your own behavior in adaptive ways; you are disgusted by others’ experiences or behaviors only because you would find those experiences or behaviors disgusting if you did or experienced them yourself. According to the traditional (non-Kurzbanian) view, this is the way morality works too, with condemnation emerging as a kind of outgrowth of a self-regulatory “conscience.” From this perspective, disgust and morality have much in common, and indeed look more or less like different flavors of the same processes. But as you and Peter have argued at length, this is exactly not the way morality works: Moral condemnation is really primary, and conscience is a kind of counteradaptation designed to avoid condemnation by others. From this perspective, disgust and morality look like such different kinds of things that it’s hard to see, at a fundamental level, what they could possibly have in common.

    That said, I think you think that the question “why are disgusting acts moralized?” is closely related to the question “why are victimless crimes moralized?”: The perpetrator 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. Your smoking pot in the privacy of your own home has no consequences for me or my fitness, but your promiscuous sexual activity (which I believe to characterize pot-smokers) does. Similarly, your f***ing a grocery-store chicken has no consequences for me or my fitness, but anyone who goes around f***ing chickens is bound to do all kinds of other awful things that probably do. In the chicken case, as in the pot-smoking case, one of those other awful things might specifically be engaging in promiscuous sex: Anyone who is so sex-crazed as to do chickens would surely have no qualms about sleeping with my wife. More generally, though, anyone who would engage in things that I (and, I would assume, any normal human being) find disgusting is clearly capable of any number of other awful things that might well have adverse consequences for me or my fitness. Such a person is simply “not right,” and surely cannot be trusted to share and abide by my values and concerns in countless other ways.

    So that’s what I think you think. And I think I think so too.

    Actually, thinking about this led me to some interesting ideas about how to answer the second question as well, but in that case I’m not sure whether I think you think the same thing or not. Lemme get back to you on that one….

    • rkurzban

      Thanks for your thoughts, Lee. You’re right about what I think in the second paragraph – I find the link more puzzling than others do – because disgust systems regulate my behavior while morality regulates others’ behavior. But I don’t then land where you do in the third paragraph. It seems to me that I could make the inferences you allude to – people who do (disgusting thing X) are likely also to do Y – without moralizing doing X. I like your argument as an explanation for why we avoid people who X, but I’m not as confident as an explanation for why we impose costs on people who X.

      • Lee_Kirkpatrick

        Fair enough, but then why do we want to punish pot-smokers rather than merely avoid them? I thought my logic was exactly the same as yours (and Peter’s) in the “Sex, Drugs, and Moral Roles” paper (thus my “I-think-that-you-think” schtick).

  • Fiddick

    Well, here’s a reason that disgusting acts are moralized — because they can potentially harm you (or your kin). Contrast actions that elicit fear vs. actions that elicit disgust and I think this becomes clearer. You ask why should someone moralize actions that only harm themselves? Good question, but there are are variety of self-harming acts that elicit fear rather than disgust and they are far less likely to be moralized — or so I suspect. But why, what distinguishes between the fear-inducing and the disgust-inducing? Contamination / disease. Disgust-inducing acts are more likely to involve pathogens. Ok, so what? Well pathogens, unlike a puncture wound, can spread from one person to another. Ever eat civet? No, neither have I, but you come near to someone who’s eaten civet infected with the SARS virus and you can die. You keep a tidy house? Ok, maybe I’m a little lacking here. But suppose you do. Too bad if your neighbor lives in filth and happens to contact the plague. But you neighbor likes to go rock climbing without any safety supports, not likely that you’ll catch that too. What about sex? Well, seems harmless at times. Ok, there is AIDS (and how did that get started? mostly likely people hunting / eating bush meats in Africa), but let’s skip this and consider something more innocuous like chlamydia. Unlike AIDS it won’t kill you, but not so fast. From an evolutionary point of view it can nearly do the same, it can make you infertile as can many (most?) STDs. How might you get chlamydia? From other people who have been sleeping around — which you yourself don’t need to do to catch it (think of the faithful wife with a cheating husband). What about homosexuality? One could speculate that this would be a contamination concern for a variety of reasons. I don’t really think there would have been the equivalent of bath-houses in ancestral environments that would have increased the spread of STDs, besides even if there were the contamination would likely be contained were it not for… homosexuals who also maintain intimate heterosexual relationships. This is more likely the problem, not homosexuality per se, but the fact that latent homosexuality would likely have been a strong motivator, even in ancestral environments, to engage in extra-pair copulations thereby spreading STDs. Contrast the “closeted” hubby with the promiscuous hubby. How would these have played out in ancestral environments. Well, then as now, males presumably prefer sexual variety and then as now males are less choosy so even in ancestral environments homosexual males would likely have had more sexual contacts. Yes, the heterosexual guys might seek variety too, but female choice constrains that. Not only that, but if, as likely, there were fewer constraints on polygyny in ancestral populations then heterosexual promiscuous tendencies probably led to the sexual monopolization of several females, but because of the monopolization, the threat of STD spread is contained. I don’t think, on the other hand, that sexual monopolization is as much of a concern with homosexuals, so there is more potential for STD spread.

    well, there’s my 2 cents

    • Lee_Kirkpatrick

      By this line of reasoning, though, why don’t we morally condemn ALL disgusting behaviors? The question really should have been stated as “Why are some disgusting acts moralized but not others?” There are lots of things people do that we find disgusting, but that we do not morally condemn or desire to punish.

      • Fiddick

        good point, but morality and disgust are not the same thing so there need not be a tight connection between them. The question Rob was posing was more why should there ever be a connection between them since disgusting acts don’t impact others. Morality might co-opt disgust in a hit and miss fashion. I tend to side with the hodgepodge view of morality, that it is a collection of somewhat unrelated phenomena.

        Actually are there really (m)any disgusting actions (in the core contamination sense) that are moralized outside of the sexual domain? (assuming that you buy that sex can pose a contamination threat — which in the case of incest isn’t so clear either, i.e. the threat is relatively contained).

        Another possibility is that the action tendencies associated with disgust (quarantine and elimination) and the “objective” nature of disgust (e.g., it is not perceived to be a matter of social consensus) are particularly useful for dealing with some immoral actors.

        • Josh

          Just a couple of brief additions to this fascinating conversation (and, really, follow-ups to the comments provided by Larry and Lee):

          Regarding Lee’s point about things like chicken copulating being a cue to potential cuckolding (or some other behavior that imposes fitness costs on others): I’m a bit skeptical that this would be a reliable cue to, say, sleeping with your wife, especially compared with other possible cues (e.g., being intrasexually dominant). I picture people who engage in what are largely agreed upon as disgusting and immoral behaviors (e.g., incest, bestiality) as not being very competitive in the mating market (though it is important to keep in mind that the direction of causality might be a bit murky – that they might be less competitive because of stigmatization, or because only a lower mate value part of the population engages in such “immoral” behaviors). Naturally, the “disgusting” behaviors that other individuals engage in could also impose other costs on third parties (e.g., if the act damages your chicken), but I think that something a little less straightforward is going on here.

          Regarding disgust toward sexual behavior and “contamination” (or, perhaps more precisely, transmission of infectious disease): I’ve noticed that evolutionarily oriented folks often mention talk about STDs when discussing disgust toward sex (though I recognize that Larry alluded to benefits to third parties of constraining STDs transmission among others). I think this is because of the intuitive link between pathogen avoidance and disgust (though also note that there are a lot of non-“STD” pathogen risks involved in sex – like the stuff that can be transmitted by touching skin and mouths). But pathogen transmission is only one of the costs of sexual behavior – only one of the selection pressures that might have led to the evolution of “sexual disgust” (so, largely, think opportunity costs, costs of stigmatization, etc). Some of these other costs might be relevant to the disgust/morality link.

          • Lee_Kirkpatrick

            Hey Josh — Lemme respond to your first point, as your second involves some more general questions surrounding “sexual disgust” that I don’t want to try to tackle now. I would argue that it doesn’t matter whether chicken-f***ers are, in reality, actual cuckold threats; all that matters is whether I believe they are. Personally, my own belief is like yours — that such people are freaks that don’t have a chance of attracting my (hot) wife — but I’d bet that many people have a different intuition: that people who would have sex with chicken carcasses are the kinds of people who would have sex with pretty much anything or anybody (including my hot wife). People’s behavior is guided by what they believe to be true, irrespective of objective reality. So I would maintain that (or, rather, I believe Rob would/should maintain that) my argument holds so long as people believe, correctly or not, that chicken-f***ers are “anything-f***ers.” (Of course, whether people actually do have such beliefs is an empirical question.)

            One nice feature of this argument is that it should be easily testable: We could determine empirically whether the degree to which a person believes that chicken-f***ing is diagnostic of potential cuckolding — versus being diagnostic of low mate value (and thus low cuckoldry threat) — is predictive of moral judgments about chicken-f***ing. I had this same thought when reading the Kurzban et al. “Sex, Drugs, and Moral Goals” paper: i.e., if their hypothesis is correct, then condemnation of pot-smoking should be predictable, at least in part, from individual differences in the belief that pot-smoking is diagnostic of promiscuous sexuality (again, irrespective of whether this is actually true or not). Maybe one of us should do that study….

        • http://popsych.org/ Jesse Marczyk

          There’s also another issue when it comes to morally condemning something like incest. While doing so is likely, then, a byproduct of a disgust mechanism, there would seem to be very little in the way of selection pushing the opposite direction (i.e. against the condemning of incestuous acts). Without any opposing force, all it needs is a little push in the right direction before it can pick up momentum.

        • Lee_Kirkpatrick

          On your first point: Part of me also sides with the hit-or-miss model — with respect to both disgust (i.e., beyond pathogen/contamination threat) and morality. For example, I am more persuaded by the idea of disgust having been co-opted by natural selection for the purpose of incest avoidance specifically than I am about it having been co-opted for a general domain of “sexual disgust” — though I’m not at this point prepared to argue strongly one way or the other (and won’t try to explain here).

          On your second point, your comment did make me realize that many things that we would describe as both immoral and disgusting fall within the sexual “domain.” But let me suggest “eating (fresh, non-diseased) human corpses” as a counter-example.

          I’m not quite sure I understand your third point, though perhaps it ties into the issue — as per Rob’s response to my initial post — of the difference between simply avoiding a transgressor (which is disgust-like) and wanting to see the transgressor punished (which is moral condemnation-like)?

  • http://www.facebook.com/profile.php?id=683550021 Roger Giner-Sorolla

    Well, when Psychological Bulletin gets around to releasing our in-press article (Russell & Giner-Sorolla) you’ll see our point of view from about a year and a half ago 😉 Basically, we argued that “disgust” felt at non-bodily moral violation is a linguistic or metaphorical slippage from the use in English and possibly other languages of “disgust” as a synonym for “anger.” Studies that carefully control for anger or use non-verbal measures that distinguish better between the two find that disgust is really felt only for moral violations of bodily norms (e.g. sex, eating). Since then, there have been other publications that challenge the absolute nature of these trends and give good evidence that true disgust toward non-bodily violations exists, though weaker than anger, so we are still in the process of working through accounts for why that happens. In general, I favor the Keltner/Haidt explanation that disgust is something that culture adapts for many purposes.

    – Roger Giner-Sorolla (not sure if my facebook ID is working here…)

  • Carlos David Navarrete

    I get bummed out sometimes when considering the evidence for theoretic meritocracy in psychology, and to some degree, this thread even makes me more pessimistic. But only because to me it seems obvious that a cleaned up version of this thread should be published in one of the leading social science journals, as the mean level of conceptual clarity here is far above reproach.

    Chuck Dave Navarrete

    PS: I think Lee K. is mostly right, even though I disagree with his standards for personal hygiene, tie-die shirts, hairstyle, etc.

    • Lee_Kirkpatrick

      Thank you Carlos, er, I think. I neither confirm nor deny these accusations. Nevertheless, the important question is whether your disgust in regard to these (alleged) habits of mine causes you to morally condemn me and wish to see me punished, and if so why.

      • C D Navarrete

        ..this is where I refer to the descriptive theory of morality foundations by Jon Haidt. I’m not a conservative, which means I tend to not moralize disgust. As such, I don’t moralize your hairstyle, and see it primarily as a social convention/preference. That said, the moralization of disgust by conservatives is definitely an issue that needs to be explained…and I think the points you’ve made here are definitely a conceptual move in that direction.

  • jessica

    Fun post and discussion. I believe both Lee_K and Rob in the original post hint at this, but I will state it directly; Not only are disgusting acts moralized (we all know how to connect the dots; bad food; taste aversion; adaptive; etc) but “moralized” acts are made “disgusting.” (stealing ex above). My favourite example is cigarette smoking. It was cool… we discovered it was bad for you (and it became a moral issue via potential harm; second hand smoke really simplifed things too)… now it’s a “disgusting habit.” It’s a two-way street (really a multidimensional causeway)
    It became not-simple (not individual level selection explicable) a looong time ago, imo. Just as (some) parents use disgust to teach–or control–their children (Don’t touch that! yuck, nasty! etc), so do powerful people (the Hopkins ex), groups (religions come to mind), societies co-opt the disgust mechanism to control others- and themselves.

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