The evolution of disgust

The evolution of disgust by Scienceline

Scienceline has a 5-minute podcast about a new theory on the origins of disgust. Most scientists think there are four categories of disgust: 1. Core disgust: protects the body from contamination ("dirt, mold, and sick people"). 2. Interpersonal disgust: protects the soul and social order ("promiscuous sex"). 3. Moral disgust: protects society ("stealing or cheating") 4. Animal reminder disgust: protects the soul from recognizing the body's animal nature. ("Death, wounds, corpses, sexuality"). But Joshua Tybur, a psychologist at the University of New Mexico doesn't think these categories are correct, at least not from an evolutionary standpoint. "It's difficult to think of natural selection actually encouraging the evolution of these kinds of terror-management, anxiety-reducing kind of activities," he says. To test his hunch,Tybur asked volunteers to write down lists of things that disgusted them. He collated the results and ended up with 105 things that disgusted people, such as seeing mold on leftovers in the refrigerator, touching a stranger's feet, hearing two strangers having sex, touching a dead body, seeing someone's bone sticking out of their leg, stealing from a neighbor, and a student cheating. Tybur eliminated items that everyone found disgusting, such as eating someone else's vomit, along with extremely specific things that disgusted only one person surveyed. That narrowed down the number of disgusting items from 105 things to 58 "uniquely gross" things. Tyler presented this reduced set of disgusting things to a new group of people and asked to rank how disgusting the things were from 0 (not all disgusting) to 6 (extremely disgusting). He found that disgust comes in three, not four, varieties: moral disgust, sexual disgust, and pathogen disgust. His conclusion: "Whereas traditional models have suggested that disgust serves to protect the self or neutralize reminders of our animal nature, an evolutionary perspective suggests that disgust functions to solve 3 qualitatively different adaptive problems related to pathogen avoidance, mate choice, and social interaction." Here's a link to a paper Tybur coauthored, titled: Microbes, Making, and Morality: Individual Differences in Three Functional Domains of Disgust Scienceline: The Evolution of Disgust


  1. erm…. what is this “soul” that this ‘scientific’ study apparently refers to?  does it have location and physical form?  (or is it an appealing form of music?)

    1. Yes, I have to agree that the inclusion of an ill-defined term like “soul” into the discourse calls the entire previous system of classification into question.  I’m glad to see empiricism rooting out the error.

  2. You know what really disgusts me? American cheese. The mere thought of it makes those little disgust muscles crinkle up my nose.

  3. Apart from the obvious and noted cringing mismatch between sentences containing the words “most scientists believe” and “protection of the soul,” I would also like to know what is the difference between the protection of social order and the protection of society and why does the first relate to sex and the other to theft.

    More on the point of substance, I wonder how does the study deal with the fact that disgust differs between cultures and is often socially conditioned. Western people find consumption of half-hatched duck eggs disgusting, the Chinese find the consumption of moldy cheeses disgusting and I don’t think most people in my country would be disgusted by the sound of two people having sex. Perplexed and embarrassed, sure. But disgusted? Hardly.

  4. That would be 2 disgusts, one is the ego, which creates ‘morality’ and then there is pathogenic disgust. 

    ‘Sexual disgust’ falls into either one of the previous 2 categories. 

    By the word ‘disgust’ i think they mean avoidance or fear. The ego will always fear, but i dont think ego is necessary for humans to survive, so these ‘disgusts’ could easily mean avoidance as well as fear of the unknown (The fear of death which is the whole religion thing where we make up stories about life after death like a heaven or hell).

    This study is kinda primitive and not very well thought out.

  5. How do they differentiate between these supposed different types of disgust? Like, if I hear two same-sex, leprous strangers having sex, how do I tell if I’m experiencing moral, sexual, or pathogen disgust? Are there some emotional feature of the ‘disgust’ that I can use to identify which one it is?

    All seems like the same one kind of disgust to me, just triggered by things we classify differently.

    I’m not sure how they went about drawing the line between pathogenic and sexual triggers. It seems to me that there could be a lot of overlap there. I have a hard time grasping the idea of ‘moral’ disgust triggers, so I don’t have much of an opinion there. 

    And as far as classifying disgust triggers, I seem to recall reading somewhere that everything is miscellaneous. But psychologists do love to classify things.

  6. Where’s racism, sexism, mass murder and terrorism on the disgust list?

    How, exactly, does promiscuous sex cause a danger to the “soul”

    Absolute crap. Pretty disgusting too.

  7. Understanding disgust, as far as I can see, is totally cultural in origin. Before anything can be disgusting, the consequences must somehow be considered harmful. This is relative to the time-scale of the feedback; the time you tried what you thought was going to be something tasty, that turned out not to be (ever bite into a Seville orange, expecting sweetness?).

    The longer the feedback loop, the harder it is to establish causation/correlation, and thereby establish some logical framework toward labelling something disgusting or not.

  8. This is one of those studies that makes me wonder what the result would be if it was done in a different language.  For all I know English is the only language that doesn’t differentiate between “Moral Disgust” and “Pathogen Disgust”.

  9. What about theoretical disgust?  Just talking about all these different flavors and examples of disgust is making me feel generally disgusted.

  10. I really don’t get disgusted by things.  Disgusted seems too strong of a word.  I don’t like having someone vomit on me, for instance; but I’m not really disgusted if it happens–I just go wash up.  I guess that’s why I always won at the game “gross out” as a kid.  I guess really putrid smells might trigger my gag reflex, but I tend to recover quickly an then ignore it.  In fact the only time I ever vomit is if I am actually sick.  I recognize things that are “bad and I shouldn’t touch, eat, or otherwise interact with” and behave appropriately… but I don’t get disgusted.

  11. Oh you would get disgusted.

    This one time, cops put us in a truck (the one to hold prisoners with no windows, dont know the exact word for it) after getting arrested in a protest. In the middle of summer, they turned up the heater to max (we could see it through a window that let you look in the drivers cabin) and then laughed it up. Someone started to get sick at some point and we started banging on the cabin for them to turn down the heat. He finally vomited and the truck was instantly filled with an overpowering smell of vomit. Other people started vomiting. Fortunatly, we were almost at the court house when he started puking.

    Im not sure why im telling you this little story. Montreal cops are “the best”

    1. Hehe, well that is an extreme case…  I imagine you could eventually overwhelm even me and make me puke…  But I would call that a physical reaction rather than disgust.  But still, I have been vomited on before an not got disgusted…  Just annoyed.  Just have a high tolerance.  I guess I fall into the category of people who become orderlies, etc. and tend to have to clean up all the disgusting things.  Although that is not my current job, I’m OK with that kind of work.

  12. How did we get this many comments and nobody has yet mentioned the difference between “disgusted” and “squicked”?

  13. I’m currently part of a reading group that is discussing Richard Beck’s book, Unclean, which deals with the psychology of disgust and particularly how it impairs our capacities for empathy towards Others and hospitality. Highly recommended.

  14. I wonder how new Pathogen avoidance is, as a common factor. I don’t know much of the cleanliness of ye ol’ times, but I get the impression that it’s really more of a modern phenomena where our disgust against many ‘pathogen’ has begun.

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