By Olivia Scheck

Whatever role one believes emotions should play in moral judgment, new research demonstrates that the influence of these low-level passions is profound. In fact, a study published in Science earlier this month suggests that many moral judgments are mediated by the same emotional mechanism that is activated by rotten leftovers and dirty socks.

“We started from this funny phenomenon where people will describe…moral offenses as ‘disgusting’…and we were wondering whether that actually means that people are feeling disgust,” explains Hanah Chapman, a graduate student in Psychology at the University of Toronto and the study’s lead author. “In its basic form [disgust] has to do with food and eating and really concrete things. So it was surprising to us that it might be involved in something as abstract as moral codes.”

To test this question, the authors used electromyography to compare the activation of facial muscles in response to bitter tastes, pictures of physically disgusting stimuli and, finally, moral transgressions. Not only was the disgust expression elicited in all three conditions, it was also shown to predict future moral decisions – suggesting not only that moral disgust exists, but that it is – to a surprising degree – driving our behavior.

Is disgust just a metaphor?

As Chapman notes, we often employ notions of disgust when describing social violations, claiming that such behaviors make us “sick” or leave “a bad taste” in our mouths. And in certain cases this makes some sense. Popular “moral” issues like abortion and sodomy may include elements of physical contamination, so it’s possible that this is what people are responding to when they describe these practices as disgusting.

But we also use these terms to describe moral violations that don’t involve physical contaminants – transgressions like dishonesty and theft. (As Adam Anderson, another of the study’s authors, points out, a Google search for “Blagojevich and disgust” yields around 49,000 hits. “Madoff and disgust” yields around 658,000.) Are we actually expressing disgust – the kind that is inspired by cockroaches and flatulence –in these instances? Or are these invocations simply metaphorical?

This is the question that Chapman et al. set out to address. In the study’s final experiment, subjects’ reactions were measured as they participated in the ultimatum game – a common economic psychology paradigm in which two subjects are asked to share ten dollars. One subject (the proposer) can offer his partner (the receiver) as much or as little of the money as he likes, keeping the rest for himself. But, if he proposes too little, the receiver may choose to reject the offer, in which case neither subject gets any money.

There is no elicitor of physical disgust in the ultimatum game. Yet, according to Chapman and her colleagues, receivers exhibit the same revolted facial expression in response to unfair offers as they do to bitter liquids and images of feces. What’s more, Anderson explains, “the degree to which you do that actually…predicts your behavior – whether you’re going to reject or accept an offer.” So, if the disgust expression does indicate the accompanying emotional state, then it appears that subjects’ decisions to reject offers are at least partially determined by feelings of disgust, rather than conscious reasoning.

How influential is disgust?
It seems obvious enough that emotions play a role in moral judgment. It is more surprising that an emotion as primitive as disgust has such an influence. (According to Anderson, even sea anemones exhibit distaste, which is the most basic form of disgust.)What is downright shocking, however, is the extent to which these responses seem to override reasoned analysis.

At least two sets of experiments, both involving the University of Virginia psychologist Jonathan Haidt, have demonstrated that inducing physical disgust makes subjects’ moral judgments about unrelated actions more severe. One of these studies, Schnall et al. (2008), asked subjects to rate the moral acceptability of characters’ behavior in four vignettes. What differed across conditions was whether subjects were making these judgments in a normal room or in a room that had been odorized with a commercially-purchased “fart-spay.” Subjects who had been surreptitiously exposed to the faux-flatulence judged the characters’ actions to be more immoral than those in the control condition – even when the vignette itself included no elicitor of physical disgust.

A second study, Wheatley and Haidt (2005), found that extraneous feelings of disgust can cause subjects to make negative moral judgments even when morally-relevant reasons are completely absent. Subjects were again asked to judge characters’ behavior in a series of vignettes. This time, though, instead of being exposed to a foul-smelling odor, subjects in the experimental condition were hypnotized to feel a pang of disgust in response to the word “often.” When the vignettes were phrased to include the disgust-eliciting word, subjects’ judgments again became more severe.

There was, however, an additional twist: one of vignettes involved no moral violation. Instead, it read as follows:

“Dan is a student council representative at his school. This semester he is in charge of scheduling discussions about academic issues. He [tries to take] topics that appeal to both professors and students in order to stimulate discussion.”

Subjects in the control condition judged – as one would expect – that Dan’s behavior was in no way immoral. However one third of subjects in the hypnotically-induced disgust condition reported that it was. Even upon reflection, these individuals fabricated justifications for their assessments. “It just seems like he’s up to something,” one subject remarked, while another declared that “[Dan is] a popularity-seeking snob.” These results demonstrate the flabbergasting degree of influence that emotions can have on moral judgment, while the Chapman findings support the notion that it is disgust, rather than general affect, determining subjects’ responses.

Washing away our sins
But a final set of experiments, conducted by Chen Bo Zhong and Katie Liljenquist, reveals the most fascinating overlap between moral behavior and sensory experience. Like the authors of Chapman et al., Zhong and Liljenquist noticed that a particular metaphor is commonly invoked to describe moral transgressions. This is the metaphor of physical dirtiness – exemplified by Lady Macbeth’s infamous cry, as she repents for the murder of King Duncan, “Out, damned spot! Out, I say!”

Noting this linguistic tendency, Zhong and Liljenquist hypothesized the “Macbeth Effect,” which predicts that “physical cleansing may actually be able to wash away moral sins.” To test their hypothesis, the authors began by asking subjects to recall in writing an unethical deed that they’d committed in the past. Then the experimenters told half of the subjects to wash their hands with antiseptic wipes. After the subjects had either cleansed or not cleansed, the experimenters presented them with a request from a fictional Ph.D. student “who had bad luck in getting funding but desperately wants to complete his study.” It is requested that the subjects participate in this second experiment for no money, in order to help out the graduate student.

“What we found,” Zhong reports, “is that participants in the no [antiseptic-wipe] condition were much more likely to volunteer to help out…presumably because their morality [was] threatened by the unethical deed that they were asked to recall, so they wanted to compensate for that….The interesting finding is that the simple act of cleansing hands removed that motivation to compensate for the past sins.” In other words, the Macbeth Effect seems to have occurred; subjects in the antiseptic wipe condition appear to have literally washed away their sins, negating the necessity for compensatory moral behavior.

Like the disgust experiments, this one demonstrates the involvement of low-level affective mechanisms in moral judgment. And, again, it reveals the shocking malleability of moral behavior by extraneous, unconscious influences. “The idea here,” Zhong explains, “is that morality is not what…philosophers…would like it to be – i.e. based on moral reasoning…Unfortunately, what my research as well as the research on disgust and morality suggest [is] that moral perceptions, moral reasoning or moral judgment…[are] very easily influenced by factors that we’re not even consciously aware of…What I hope to have as a consequence of this [work] is that people can take control of their moral regulation.”

The proper role of emotion

Indeed, one lesson to take away from this literature is that we should attempt to limit the influence of low-level emotional mechanisms on moral judgment and behavior. But these findings also demonstrate the importance (if not the essentiality) of emotions for human morality.

Consider what it would be like if we lacked emotional responses to moral situations. This is to some degree the case for people with anti-social personality disorder – or, as they are colloquially known, psychopaths. These individuals are not famous for their insusceptibility to disgust and cleanliness primes, but rather for their propensity to perform immoral acts – donning hockey masks and hacking up suburban teenagers.

So, although we may always be in some sense feeling our way to right and wrong, we can at least regulate which factors influence these decisions – ignoring the influence of superfluous disgust primes, but remaining open to the draw of others’ suffering. Passions may be an essential part of moral judgment, but reason need not be their slave.