This is the second in a series of interviews with Purdue professors discussing their recent publications. This time we interviewed Daniel Kelly, an assistant professor of philosophy, about his book released in June, "Yuck! The Nature and Moral Significance of Disgust."

1) How did you become interested in the topic of disgust?

Part of what got me interested in philosophy in the first place were questions about what makes people tick, how humans are continuous, but also distinct from other creatures in nature, and (of course) What It All Means. While I was in graduate school, exciting new research was taking place at the intersection of philosophy and the cognitive sciences, specifically in moral psychology. As I looked into that, I saw that some of the most interesting work was exploring the surprising link between disgust and morality. It was a promising area for the type of conceptual contributions a philosopher could make, too, since it seemed that people from different disciplines and perspectives where saying things about the emotion that were equally plausible, but that also looked incompatible with each other.

2) Is there any back story behind how you chose the jacket cover picture or what the picture is supposed to represent?

The key to the cover is the expression that guy is making at his glass of water (or whatever liquid nastiness is in there). Since that "gape face" is instantly recognizable as an expression of disgust, it grabs the eye and gives a little punch to the book. I had always wanted some depiction of that facial expression to appear on the cover, but that particular picture was actually found by one of my editors at The MIT Press, and I've come to really like it. The picture I initially wanted on the cover was of a painting of someone making that expression done by friend Karl-Erik, but his style - which is sort of cubism meets Edvard Munch - is beautiful but abstract, and the expression in his painting wasn't as obvious. I love Karl-Erik's painting - it's hanging in my living room - but given the number of compliments I've gotten on the picture that ended up on the cover, I think we were right to go with this one.

3) What was the process like to research and finish the book?

The book grew out of my dissertation, and so it's gone through a lot of iterations. Part of what made it so challenging and absorbing was that I got to read and try to pull together evidence and strands of thought from a bunch of different disciplines, from cognitive neuroscience to evolutionary theory to social psychology to philosophy of mind to normative ethics. I was pulled out of my comfort zone pretty regularly, but it was also really invigorating to try to figure out how all of the different pieces might fit together.

4) How is disgust different today than it was in early human history?

It's hard to know for sure, but a plausible idea is that one thing that *doesn't* differ much is the disgust response, what happens to a person on a physiological level (a flash of nausea), psychological level (concerns about taint, purity and contamination), and behavioral level (making that gape face) when he or she is disgusted by something. That appears to be pretty stable. On the other hand, there can be a lot of variation in the types of things that activate that response in people from different eras and cultures. People living in a tribe in sub-Saharan Africa 10,000 years ago likely felt the same emotion we do, but it obviously wasn't things like the moral bankruptcy of ambulance chasing lawyers or a meal of jellied moose nose that triggered it. (Yes, jellied moose nose is really a thing; no I haven't tried it.)

5) What are some of the most disgusting tangible items to people in Western culture?

Some of the most disgusting tangible items in Western cultures are probably some of the most disgusting items in any culture, because they're probably innately disgusting. Things like excrement, rotting meat, decomposing corpses, and other types of organic decay have a good claim on being both extremely and universally gross. Also, other people bearing the marks of sickness or infection are also good bets to be really foul - pus-filled sores, sweating, hacking and sneezing, that sort of thing. And if you want to make something that's disgusting seem even more revolting, image licking it or putting it in your mouth. Ew.

6) What are some of the most disgusting thoughts or concepts to people in Western culture?

There's some controversy about whether abstract thoughts or ideas trigger genuine disgust in people of any culture, or if their professed disgust is just metaphorical. "The price of a gallon of gas these days is disgusting!" Someone who announces this clearly means to express vehement outrage, but is he really disgusted, like in the same way he would be if he found dog turd on his shoe? I think so, but the jury's still out on these types of cases. That said, certain forms of injustice, hypocrisy or violations of a culture's core values can elicit pronouncements of disgust from members of that culture. This is evident even within subgroups of our own culture, where the more abstract triggers of disgust and other powerful emotions tend to vary a lot with political orientation. You might find the people and values lined up on the opposite side of a "wedge issue" slightly disgusting.

7) How do the things that disgust Western culture different from other cultures?

We're just beginning to study questions like these systematically, so it's hard to say with much detail or confidence. One good place to start is with food, though. What is considered a delicacy, or is central to the cuisine of one culture (think sushi, or escargot, or vegemite, maybe), can be considered disgusting to people from other cultures. Anthropologists and cultural psychologists have also suggested that some cultures have "divinity" focused moral systems that are very different from the "autonomy" centered system common in many Western cultures. The thought is that in those cultures disgust is more front and center than in our own, and plays a much more prominent role in shaping morality and regulating social interactions that it does here.

8) How does studying the things we're disgusted about inform us about our culture as a whole?

I actually think the big picture is the most informative, and that it's most interesting to think about how all of the phenomena linked to disgust are connected to each other - the features of the response itself, the subliminal influence it can exert over other parts of our psychology, the way it can scale up to shape social dynamics, what might be innately disgusting and why, the significance of the patterns of within group similarity and between group variation in what disgusts people, and everything else. It's a single emotion, but it can act as an entry point for addressing a wide range of questions about human nature and our biological, psychological, and cultural evolution.

9) Is there anything else you would like to add? Or something we didn't cover that you think is important for people to know?

One of the messages of the book is that we should minimize the role disgust plays in morality as much as we can. As a matter of fact disgust sometimes influences the psychology of morality, but we shouldn't celebrate this fact. As a matter of ethics, we shouldn't grant the emotion any kind of moral authority. First, we tend to dehumanize what we find disgusting, and dehumanizing other people is obviously not something we want to promote. Second, I think the mere fact that a practice is disgusting to you (or to anyone else) doesn't provide a good reason or justification in support of the claim that the practice is morally wrong. As powerful and vivid as that yuck feeling can be from the inside, the mere activation of this emotion is really just irrelevant to whether or not your moral assessment of the practice that triggers it is correct or justified.


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