Fart Spray (And Disgust) Makes Moral Judgments More Severe

I've been meaning to post about this set of studies for a while, but because it's relevant to Chapter 4 of Lakoff's The Political Mind, I figured I'd better get around to it before I write the review of that chapter.

It's been a while, but in the past, I've talked a lot about new theories of moral judgment, and Jonathan Haidt's social intuitionist model in particular. Under Haidt's view, moral judgments are largely intuitive (that is, unconscious, automatic, and non-deliberative), and instead of being based on ethical principles, which we use mostly for post-hoc rationalization, they're based largely on emotion. In expounding and (occasionally) testing his theory, Haidt has focused largely on what he calls the "moral emotions," and in empirical tests, he's focused on one of these emotions in particular: disgust.

In a study published in 2005, Wheatley and Haidt (1) showed that hypnotically-induced disgust led people to judge people's moral infractions more harshly. In a study published this year, Schnall et al. (2) replicated and expanded on this finding, but without hypnosis. In their first study, participants read little vignettes like these(from their appendix, p. 1107):

Some U.S. states allow first cousins to marry each other. The state you live in does not currently permit first-cousin marriages but is considering legalizing them. What do you think about such legislation?

How moral or immoral do you, personally, find consensual sex between first cousins to be?

Participants were asked to answer these questions (and similar questions for other vignettes) on a 1-7 scale (7 always meant "perfectly okay," or the equivalent).

In their first experiment, participants read the vignettes while being exposed either to a lot of fart spray ("strong stink" condition), a little fart spray ("mild stink" condition), or no fart spray (control). The fart spray was supposed to induce disgust, which, under Haidt's theory, is associated with immorality. Therefore, the fart spray should increase the severity of moral judgments. Consistent with this hypothesis, for three of the five vignettes in the mild stink condition, and two of the five in the strong stink condition, participants' acceptability ratings (i.e., they rated actions like sex with a first cousin as being more immoral) decreased relative to the control condition.

In a second experiment, Schnall et al. explored the role of people's sensitiveness to their own sense of disgust in the influence of disgust on moral judgments. This time, the disgust was induced by the environment. I'll give you their description:

For the disgust condition, a workspace was set up to look rather disgusting: An old chair with a torn and dirty cushion was placed in front of a desk that had various stains and was sticky. On the desk there was a transparent plastic cup with the dried up remnants of a smoothie and a pen that was chewed up. Next to the desk was a trash can overflowing with garbage including greasy pizza boxes and dirty-looking tissues.

In other words, the disgust condition took place in a typical grad student's office. Ha! They cleaned the room up for the control condition. Participants read the vignettes in one of the two conditions, and before they were left, they completed the "Private Body Consciousness" scale, which is supposed to measure how aware people are of their own "gut feelings" (as Schnall et al. call them).

In this study, Schnall et al. found that, for participants with high "private body consciousness" scores (that is, high awareness of their own internal feelings), disgust significantly increased the severity of their moral judgments overall, while for participants with low "private body consciousness," there was no effect of disgust on the severity of their moral judgments. They replicated this result in a third experiment involving a different disgust manipulation (having participants write about a disgusting experience).

Finally, in their fourth and final study, Schnall et al. added a sadness condition, to show that the effects observed in the previous study were specific to disgust. In this experiment, sadness and disgust were induced by watching videos previously shown to induce those emotions. Replicating the previous studies, the disgust-inducing video increased the severity of moral judgments. Participants who'd watched the sad video produced judgments that were actually less severe (though this result only approached statistical significance) than those of participants in the control condition. So, it's not just negative emotions in general that produce more severe moral judgments, but disgust in particular. Some negative emotions might even make us less severe in our moral judgments (perhaps by eliciting empathy? who knows).

In sum, Schnall et al. found in four studies that, at least for participants who are aware of their feelings, disgust consistently produces more severe moral judgments relative to a control condition. Schnall et al. interpret this finding as suggesting that the feeling of disgust is closely tied to negative moral judgments. Moral emotions, under their view, tell us whether we like or dislike something, and disgust in particular signals a deep dislike of something. So, when we feel disgust, we assume that we dislike something, and when moral questions are involved, this leads us to seeing it as immoral. As they put it, disgust is "embodied moral judgment."

¹Wheatley, T., & Haidt, J. (2005). Hypnotically induced disgust makes moral judgments more severe. Psychological Science, 16, 780-784.
²Schnall, S., Haidt, J., Clore, G.L., ^ Jordan, H. (2008). Disgust as embodied moral judgment. Personality and Social Psychology Bulletin, 34(8), 1096-1109.