Evolutionary psychologist Diana Fleischman, PhD knows disgust. When we read about her recent study, "Disgust versus lust," in which Fleischman showed women disgusting stimuli, such as images of human corpses and feces to measure the effects of disgust on women's sexual arousal, we had to ask her why, exactly, she embarked on this particular line of inquiry.
Fleischman explained that she has always been fascinated by what others find gross. "I've always been very disgust-insensitive," she told us. "I love making gross jokes; I talk about things over dinner that people don't want to talk about, and I have to kind of check in with people!" When her research advisor encouraged Fleischman to "carve out a niche," disgust — thought to have evolved as a "protective" emotion, as it repels us from things that might transmit disease — was a natural choice. For their latest research, Fleischman and her team worked with 76 heterosexual women ages 18 to 42, showing one group disgusting images followed by porn; a second group porn followed by disgusting images; a third group frightening images followed by porn; and a fourth group porn followed by frightening images. Each woman wore a "photoplethysmograph," a tampon-like device that measures vaginal blood flow and thus arousal, during her visual adventure.
The conclusion: Women exposed to disgusting stimuli before watching porn were three times less aroused by that erotic stimuli than those in other groups. And there were no significant differences in arousal between women who had viewed frightening images before porn, and women who had not — indicating that being grossed out has a substantial negative effect on your desire to get it on. We chatted with Fleischman to learn more about why (and how) she and her team selected just the right horrifying images for the study.
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First of all, why did you get into the disgust game?
"I have an interesting history with disgust. My mother is incredibly disgust-sensitive. She would wash me in boiled water and alcohol, and was very, very sensitive about any kind of germs that I would come into contact with, and I've always been very disgust-insensitive, like my dad... I'm really interested in fecal transplants [for example]... I just think it's so interesting because there are all kinds of medical applications, and I have to remind myself that people don't necessarily want to hear about it! [laughs] I'll eat stuff of the floor, it doesn't matter to me. And disgust is not necessarily something people want to investigate. It's really important, because, for example, people are not that inclined to donate to deworming in the developing world because they don't really know what that's like, and they don't want to think about it, whereas other kinds of causes are much more popular. So, I think [understanding disgust is] important for a variety of reasons, including moral reasons. My advisor [at university] always said, 'You should carve out a niche,' and that's what I thought I would do with disgust."
"I have an interesting history with disgust. My mother is incredibly disgust-sensitive. She would wash me in boiled water and alcohol, and was very, very sensitive about any kind of germs that I would come into contact with, and I've always been very disgust-insensitive, like my dad... I'm really interested in fecal transplants [for example]... I just think it's so interesting because there are all kinds of medical applications, and I have to remind myself that people don't necessarily want to hear about it! [laughs] I'll eat stuff of the floor, it doesn't matter to me. And disgust is not necessarily something people want to investigate. It's really important, because, for example, people are not that inclined to donate to deworming in the developing world because they don't really know what that's like, and they don't want to think about it, whereas other kinds of causes are much more popular. So, I think [understanding disgust is] important for a variety of reasons, including moral reasons. My advisor [at university] always said, 'You should carve out a niche,' and that's what I thought I would do with disgust."
Why the choice to include fear stimuli in a study on the effects of disgust on female sexual arousal?
"Weird thing about fear is that if you show women something like a bit of a film clip, where a woman is being chased by a strange man or something, that actually tends to increase arousal. If you tell women on the other hand, ‘You may get an electric shock once every 10 minutes,’ that doesn’t increase arousal. What we did is, we used ecologically valid fear stimuli that people might really be afraid of in real life — so fires, dangerous animals, stuff like that. Because disgust is a negative emotion, we were interested in whether or not fear — also a negative emotion — might show a similar effect. It was sort of our control, and it wasn’t really meant to be an experimental condition of itself… We didn’t want people to say ‘Oh, well, you showed women disgusting stimuli and then you showed them pornography, they just felt bad, that’s why they showed a decreasing arousal.’ We wanted to show that it was specific to disgust. People feel bad after they view fear stimuli and after they view disgust stimuli, but the bad feelings are different. That’s what we wanted to explore." What makes certain kinds of fear sexy, so to speak?
"Part of it has to do with the kind of nervous system activation. Maybe [these stimuli] kind of get your blood flowing, and then the measure of arousal we used is connected to circulation, so it’s how much blood flow there is to the vagina. We didn’t actually show that the fear condition was greater than the control condition — they were statistically similar [in how turned on the women were after exposed to each]; what we were interested in with these fear stimuli, is that these were things that were actually encountered, potentially ancestrally, that would have actually been dangerous." As for the disgust stimuli, there was some pretty, well, disgusting stuff in there — people vomiting, diseased and deceased humans, and more. How did you decide what to show people?
"There’s this thing called the International Affective Picture System, or IAPS, and they are a bunch of images that you are actually not allowed to put online because they use them for studies. There’s something like 600 images, and you sign a thing saying you won’t use them for anything else. Most of the images came from there, and we had to select, I think, 60 images that we had people rate for how sexual, how fear-inducing, and how disgusting they were. There was a really horrible picture that was in our disgust file of a diseased penis, and we didn’t want to put something like that in there because that was sexual and disgusting — so we wanted to keep it really constrained to stuff that was connoting disease and sickness, as opposed to stuff that was connoting sexual disease." Tell me more about the “photoplethysmograph” you used to measure women’s arousal.
"We just call it the 'probe,' because it's a lot easier than saying all that! 'VPA' [Vaginal Pulse Amplitude] is the term [for what it measures]. It's interesting because for men, they have this loop that they put around a man's penis, and then the more erect he is, it changes the loop, whereas for women, it's this different measure of the blood flow to the genitals. What the probe does is, it shoots out light into the vaginal canal, and then the more dilated your blood vessels are — I don't know if you've ever put a flashlight underneath your hand and you can see your hand glow red — it's kind of like that. The more dilated the blood vessels are in the genitals, the less light comes back, and the more light is absorbed. So, we are measuring how much light is coming back to the probe. The light measure gets at the blood flow measure. Women did also self-report their arousal, [but] self-reported arousal doesn't always correspond well to physiological arousal. But women who have sexual dysfunction tend to also show less physiological arousal."
"Weird thing about fear is that if you show women something like a bit of a film clip, where a woman is being chased by a strange man or something, that actually tends to increase arousal. If you tell women on the other hand, ‘You may get an electric shock once every 10 minutes,’ that doesn’t increase arousal. What we did is, we used ecologically valid fear stimuli that people might really be afraid of in real life — so fires, dangerous animals, stuff like that. Because disgust is a negative emotion, we were interested in whether or not fear — also a negative emotion — might show a similar effect. It was sort of our control, and it wasn’t really meant to be an experimental condition of itself… We didn’t want people to say ‘Oh, well, you showed women disgusting stimuli and then you showed them pornography, they just felt bad, that’s why they showed a decreasing arousal.’ We wanted to show that it was specific to disgust. People feel bad after they view fear stimuli and after they view disgust stimuli, but the bad feelings are different. That’s what we wanted to explore." What makes certain kinds of fear sexy, so to speak?
"Part of it has to do with the kind of nervous system activation. Maybe [these stimuli] kind of get your blood flowing, and then the measure of arousal we used is connected to circulation, so it’s how much blood flow there is to the vagina. We didn’t actually show that the fear condition was greater than the control condition — they were statistically similar [in how turned on the women were after exposed to each]; what we were interested in with these fear stimuli, is that these were things that were actually encountered, potentially ancestrally, that would have actually been dangerous." As for the disgust stimuli, there was some pretty, well, disgusting stuff in there — people vomiting, diseased and deceased humans, and more. How did you decide what to show people?
"There’s this thing called the International Affective Picture System, or IAPS, and they are a bunch of images that you are actually not allowed to put online because they use them for studies. There’s something like 600 images, and you sign a thing saying you won’t use them for anything else. Most of the images came from there, and we had to select, I think, 60 images that we had people rate for how sexual, how fear-inducing, and how disgusting they were. There was a really horrible picture that was in our disgust file of a diseased penis, and we didn’t want to put something like that in there because that was sexual and disgusting — so we wanted to keep it really constrained to stuff that was connoting disease and sickness, as opposed to stuff that was connoting sexual disease." Tell me more about the “photoplethysmograph” you used to measure women’s arousal.
"We just call it the 'probe,' because it's a lot easier than saying all that! 'VPA' [Vaginal Pulse Amplitude] is the term [for what it measures]. It's interesting because for men, they have this loop that they put around a man's penis, and then the more erect he is, it changes the loop, whereas for women, it's this different measure of the blood flow to the genitals. What the probe does is, it shoots out light into the vaginal canal, and then the more dilated your blood vessels are — I don't know if you've ever put a flashlight underneath your hand and you can see your hand glow red — it's kind of like that. The more dilated the blood vessels are in the genitals, the less light comes back, and the more light is absorbed. So, we are measuring how much light is coming back to the probe. The light measure gets at the blood flow measure. Women did also self-report their arousal, [but] self-reported arousal doesn't always correspond well to physiological arousal. But women who have sexual dysfunction tend to also show less physiological arousal."
Why are women more likely than men to experience disgust in sexual contexts than men?
"There's a lot more risk of sexually transmitted infection for women, and the disease burden is much greater... Sexual contact happens in stages. Maybe when you're sexually aroused, something can happen where you get close enough to somebody to smell them or something, and then you're like "Oh no, you actually are diseased, and I should now be disgusted." For men, there's a lot less risk and a lot more reward [from sexual activity]. And for women, there's a lot more risk and much less reward because women can only have a certain finite number of offspring in their whole lives, whereas men can have hundreds of offspring, if they get the opportunity. It's a matter of risk and reward, and I do think that for women, sexual arousal might not do as much to dampen the disgust response. In the act of sex itself, the further you go, the more risk you are engaging in." What's next for you?
"I have a colleague studying olfaction, so what we were thinking about doing is a study comparing men and women on how disgusting they find smells when they're sexually aroused. We're also interested in how people respond to sexually disgusting scenarios when they're drunk! One idea is that people are less disgust-sensitive when they're drunk, and so then they engage in more risky sexual behavior, especially when it comes to infection transmission."
"There's a lot more risk of sexually transmitted infection for women, and the disease burden is much greater... Sexual contact happens in stages. Maybe when you're sexually aroused, something can happen where you get close enough to somebody to smell them or something, and then you're like "Oh no, you actually are diseased, and I should now be disgusted." For men, there's a lot less risk and a lot more reward [from sexual activity]. And for women, there's a lot more risk and much less reward because women can only have a certain finite number of offspring in their whole lives, whereas men can have hundreds of offspring, if they get the opportunity. It's a matter of risk and reward, and I do think that for women, sexual arousal might not do as much to dampen the disgust response. In the act of sex itself, the further you go, the more risk you are engaging in." What's next for you?
"I have a colleague studying olfaction, so what we were thinking about doing is a study comparing men and women on how disgusting they find smells when they're sexually aroused. We're also interested in how people respond to sexually disgusting scenarios when they're drunk! One idea is that people are less disgust-sensitive when they're drunk, and so then they engage in more risky sexual behavior, especially when it comes to infection transmission."