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A plate of food overrun by roaches. A blood-encrusted scab. The squish of dog poo under one’s shoe. In this talk from TEDxEast, David Pizarro explains that each of these images elicits disgust, a visceral emotion that serves a good purpose — to keep us away from harmful substances. But disgust may in fact do much more than that.

“A growing body of evidence suggests that this emotion of disgust influences our moral beliefs and even our deeply held political intuitions,” says Pizarro, a professor of psychology at Cornell University. “It works through association. When one disgusting thing touches a clean thing, that clean thing becomes disgusting — not the other way around. This becomes a very useful as a strategy if you want to convince someone that an object, or an individual or an entire social group ought to be avoided.” As Pizarro points out, Nazi propaganda described Jews as smelling terrible while, more recently, anti-gay websites conjure up images of “vile sex acts.”

Pizarro and his team wondered if certain people were more likely to be swayed by these kinds of appeals. They looked at the variable of “disgust sensitivity” and found that, across three studies, those who reported feeling easily disgusted were more likely to also report themselves as politically conservative. In fact, a larger survey of Americans showed that disgust sensitivity could even be used as a predictor for how people voted in the 2008 election. The same basic pattern held across 121 different countries.

And it could be a causal relationship. Researchers have shown that when people feel disgusted in lab scenarios, they shift to more stringent socio-moral judgments. As Pizarro describes, just taking a survey in the presence of a sign touting the importance of hand washing was enough to have this effect.

To hear more about Pizarro’s studies — including one which showed that the presence of a bad smell upped negative attitudes toward gay men — watch his talk. Below, some more recent findings in the growing body of disgust research.

1. Arousal may be one of the few things that can tame disgust. Sex doesn’t seem disgusting in the moment and yet, out of context, the fluids and smells associated with it are rated as revolting. A recent study from researchers at The University of Groningen in The Netherlands looked at the interplay between disgust and arousal. They studied a group of 90 women, seeing whether their agreeableness towards performing disgusting tasks (for example, drinking from a glass with a bug in it or cleaning an unused sex toy) would change depending on whether the participant had been shown arousing materials. Their findings suggest that arousal may in fact override feelings of disgust for women. [Plos One]
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2. Disgust can effect how you shop for groceries. Certain products — like trash bags, diapers, and toilet paper — make people feel just a little icky. Researchers Andrea Morales and Gavan Fitzsimons, of Arizona State and Duke University, wondered if this might effect how people shopped at a supermarket. In tests, they found that even the most delicious of items — say, cookies — seemed disgusting when they had come within an inch of the undesirable items. The pair published the implications for grocery store aisle design in the Journal of Marketing Research in May of 2007. [Time.com] And more recently, the pair looked at whether disgust makes people more susceptible to fear appeals often made in commercials and ads. [Marketing Power]
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3. For women, disgust may be linked to hormonal cycles. Daniel Fessler of The University of California Los Angeles has long been curious about why pregnant women are so easily disgusted, and has linked their disgust sensitivity to the hormone progesterone. Progesterone is known to spike in a woman’s first trimester, and Fessler hypothesizes that this might help protect the fetus when it is most susceptible. [NY Times] But Fessler’s newest study, conducted with Diana Fleischman of The University of North Carolina, shows that women may be affected by this hormonal connection even when not pregnant. The pair looked at the luteal phase of the menstrual cycle, when progesterone fights off inflammation that could prevent an implantation. The two see a potential link — as the body becomes more hospitable to an embryo, it also cranks up disgust responses to protect it from outside contamination. [Hormones and Behavior]
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4. Disgust might explain weight bias. People who are overweight are often stigmatized and discriminated against. In a study published in the International Journal of Obesity, Lenny Vartanian of The University of South Wales in Australia looked at whether disgust might be a factor in this poor treatment. He asked participants to assign ratings of disgust to obese people, as well as to other social groups including smokers, drug addicts, women, homosexuals and politicians. Not only did participants rate those who were obese as more disgusting than almost all the other groups — this also correlated with how much control they believed obese people have over membership in the group. [Nature.com]

To read lots more about disgust research, read The New York Times article “Survival’s ick factor,” or look at the list of speakers from the conference “The Evolution of Disgust,” held last January.