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Easily Disgusted? You May Have a Better Built-in Filth-o-Meter

If Tub Girl made you barf, you might be more able than others at finding grime.

There's a reason why legendary gross-out internet memes like Goatse and Two Girls, One Cup are almost universally gag-inducing. It's how we're engineered. Disgust, notes Brown psychologist Rachel Herz in her recent book, That's Disgusting, is one of six basic human emotions–among them, happiness, fear, anger, sadness and surprise–but it's the only one that's learned.

It is "an unfolding and cognitive emotion," she writes: One that "protects us from creeping dangers that we have to figure out, dangers that are slow in their deadliness, and of which disease, contamination and decomposition are the foremost threats." (Note: quotes from Herz's book were pulled from a nice review in The New York Times by Robin Marantz Henig.)

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Things like feces and gaping orifices can spread disease, which may explain why most of us find the aforementioned internet memes so revolting. But note that I said "most of us." Because we all grow up differently, what disgusts us is also to some degree subjective. And now, a study published in Psychological Science, indicates that increased emotional sensitivity to disgust may make us better perceive things that are impure, i.e. things that could harm us. And for people who are easily grossed out, actually feeling disgusted may heighten their awareness of perceived impurities.

Based on previous research about the "psychology of purity," co-authors Gary Sherman, a psychological scientist at Harvard's Kennedy School of Government, and psychology professors Jonathan Haidt and Gerald Clore, note that when something looks dirty, we conclude that it is probably impure (hence, dangerous) in some way–like a dirty toilet seat. When that toilet seat is white, we perceive it as clean. It may explain our preference for many things white–from white napkins and teeth to white dishes and hospital walls. (Hold the racial inferences, please, and keep reading; they don't apply.)

This still stands as one of the best videos ever. I bet she has clean toilets.

The authors hypothesized that people with a more finely-attuned sense of disgust may also be better at distinguishing subtle derivations in shade at the light end of the gray-scale spectrum. In practical terms, they could literally see the grime collecting on the toilet seat better than those with less sensitivity to disgusting things.

To test this, they used a survey to measure the disgust sensitivity of 123 college students, then presented them with several series of four rectangles. In each set of four three were of exactly the same gray-scale value, with the fourth representing a very slight variation in lightness or darkness. Subjects were asked to identify which of the rectangles was different from the others. In a second study, the subjects were shown panels depicting a number placed upon a background of almost identical gray-scale value and asked to identify the number.

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In both experiments, people generally had an easier time making the distinctions at the darker end of the spectrum. But subjects who exhibited a relatively better aptitude at the lighter end were also significantly likely to have a greater sensitivity to disgust. In other words, they both saw and felt impurity more strongly. (Experimenters also measured sensitivity to fear as a control; it had no correlation with perceptive abilities.)

But which causes which? Do you see the dirt on the toilet seat better because you're more easily grossed out, or vice versa? The causal direction for is uncertain in the long-term. Still, Sherman and Haidt guessed that heightening a puke-prone person's sense of disgust might change their perceptive ability in the moment.

Researchers showed their subjects several images of typically disgusting things like cockroaches and rotting garbage (again, with fearful images as the control). True to the hypotheses, subjects who were more disgust-prone did significantly better at perceiving variations at the light end of the scale after they were shown the images than before. Their physical senses had been "tuned" to perceive impurities more keenly. (For those with low disgust sensitivity, seeing the images had no significant effect on their perceptive abilities.)

It's an interesting addition to the already abundant evidence that emotion changes the way we "see" things. In 2009, psychologists Jeanine K. Stefanucci and Justin Storbeck found that creating an emotional arousal (PDF) in people made them overestimate the distance from a second-story balcony down to a target below compared to control groups. And ask any criminal prosecutor whether fear influences one's perception of the height or ugliness of a criminal.

But there's a crucial difference here. As the new study's authors note, "research on the experience-altering nature of emotion has typically focused on nonperceptual experience, such as changes in cognitive appraisals. It is clear, however, that these influences extend to perception." Indeed, assessing balcony height or criminal height involves calculation; distinguishing panels and numbers based on minute tint and shade variance involves no calculation, only eyesight.

One can only imagine the implications extend to the other senses as well. It may be what's happening when people say they can't eat anymore after someone describes Two Girls, One Cup at dinnertime. Although, if that's dinnertime conversation in your home, you may have more pressing worries.

Top image via Shutterstock