Disgust in the 21st C. -- 1

Disgust: The body and soul emotion in the 21st century

Paul Rozin

University of Pennsylvania

Jonathan Haidt

University of Virginia

Clark McCauley

Bryn Mawr College

This article was published as chapter 1 of an edited volume. The citation is:

Rozin, P., Haidt, J., & McCauley, C. R. (2008). Disgust: The body and soul emotion in the 21st century. In D. McKay & O. Olatunji (eds.),Disgust and its disorders.Washington DC: American Psychological Association. P. 9-29.

Disgust: The body and soul emotion in the 21st century

The present volume is, we believe, the first-ever edited volume devoted to the emotion of disgust. In this chapter we address the following issues: 1. Why was disgust almost completely ignored until about 1990, 2. Why has there been a great increase in attention to disgust since about 1990?, 3. The outline of an integrative, body-to-soul preadaptation theory of disgust, 4. Some specific features of disgust that make it particularly susceptible to laboratory research and particularly appropriate to address some fundamental issues in psychology.

In the final section, we outline some new questions that arise from the recent increased interest in disgust in the areas of brain mechanisms, psychopathology, the psychometric approach to the structure of disgust, and disgust and morality. We then indicate some important aspects of disgust that have yet to receive systematic investigation.

Why the delay? A Century of Ignoring Disgust

Disgust got off to a good start in Charles Darwin’s classic, The expression of the emotions in man and animals (1998/1872). Darwin listed disgust as one of 32 emotions and made it an important component of Chapter 11, “Disdain – Contempt – Disgust – Guilt – Pride, etc.” He even included a page with drawings of disgust expressions. As emotion research developed within psychology, however, disgust (and most of the other emotions mentioned by Darwin) dropped out of the picture. Attention converged on sadness, anger and fear (and only recently on happiness as well).

Thus, in William James’ (1890) classic chapter on emotion, the word disgust (disgusted/disgusting) is mentioned 3 times, in comparison to anger/angry (20 times, plus 11 for “rage”), and fear/afraid/fright (42 mentions). We examined the indices of 15 major introductory psychology textbooks from 1890 to 1958 (The titles of these texts, a convenience sample of the texts available in the University of Pennsylvania library, are listed in the notes to Table 2, p. 368, of Rozin, 2006) indicates a total of 5 page references to disgust, as opposed to 46 for anger and 85 for fear.

This lack of interest in disgust is surprising because disgust meets the standard criteria for being a basic emotion as well as any other candidate, according to the criteria set forth by Ekman (1992), and it is usually included in lists of basic emotions, which typically also include anger, fear, happiness, sadness, and surprise. The landmark books on emotion (Izard, 1977; Lazarus, 1991; Plutchick, 1980; Tomkins, 1963), give considerable attention to disgust, and there is one classic paper (Angyal, 1941). But, as a topic for either research or attention in the teaching of psychology, disgust was almost absent during the 20th century.

This absence in the more recent literature was documented by Olatunji and Sawchuk (2005), who carried out a search for anger, fear, and disgust on the PsycInfo reference data base from 1960 to 2003. There were virtually no papers on disgust until the 1990s.

There is no simple explanation for this neglect but four factors may have contributed.

First, all human endeavors, starting with perception/attention, involve information overload and filtering out most of the input. Limited cognitive resources for humans and limited human resources for research in academic psychology virtually require a selection of a small subset of possible topics for study and attention (Rozin, 2007a). So, of Darwin’s 32 candidate emotions, it is not surprising that only a few became the targets for major research programs.

Second, fear is easy to see and study in other animals, and is obviously fundamental in many forms of psychopathology. Anger as a source of violence has clear relevance to social problems. So it is not surprising that fear and anger receive much more attention than disgust. As already noted, from William James onward, psychologists have focused on fear and anger in trying to understand both everyday problems and pathologies.

A search of two linguistic data bases (from the Linguistic Data Consortium [www.ldc.upenn.edu]--a very large compendium of English language news sources, and a more modest base of spoken English sampled from transcriptions of telephone conversations--reveals the following. In the news database, there were 17,663 citations to disgust (disgust, disgusted, disgusting), compared to 177,018 for anger/angry, and 285,194 for fear/afraid. That is, relative to disgust, citations to anger were 10 times more common and citations to fear were 16 times more common. In the conversation data base, however, the ratios were 1.4 to 1 for anger and 7 to 1 for fear. These lower ratios suggest that in common speech disgust is relatively more frequent than in writing.

A third reason may be that disgust, as its name suggests, is particularly associated with food and eating. Psychologists have sought general mechanisms of behavior rather than focusing on specific domains of life (Rozin, 2006), and the food domain, in particular, has received very little attention (Rozin, 2006. 2007).

A fourth reason for disgust avoidance may simply be that disgust is disgusting. Pelham, Mirenberg, and Jones (2002) demonstrated that tiny flashes of affective positivity influence people to choose marriage partners and careers whose names resemble their own (e.g., men named Lawrence are more likely than average to become lawyers and marry women named Laurie). It seems likely, therefore, that when graduate students choose research topics, many are steered away from the revolting subject matter of disgust.

Thus psychologists’ weak attention to disgust may be a result of some combination of the following factors: disgust was lost in Darwin’s long list of emotions; disgust lost out to fear and anger in the race to be relevant to human problems; disgust was seen as relevant to only that narrow part of human behavior related to food and eating; and disgust research is avoided as disgust is avoided.

Why Now?: Documenting the Rise of Interest in Disgust

The analysis by Olatunji and Sawchuk (2005) indicates a notable rise in disgust citations in the 1990s, stabilizing at around 50 a year in the last decade. Compared to levels of about 500 for anger and 1200 for fear, the level is still modest but the increase is impressive. In this time period, disgust seems to have assumed the place that would be accorded to it in terms of its relative frequency in English-language news sources although still well below the level of English-language conversations (both estimated from the Linguistic Data Consortium, see above, www.ldc,upenn.edu),

We are not aware of any academically oriented books on disgust before 1997, but, since the publication of William Ian Miller’s (1997) The Anatomy of Disgust, there has been at least one other book focused on disgust (S. Miller, 2004), and two well-regarded psychology trade books with prominent attention to disgust (Bloom, 2004; Pinker, 1997). Interest in the involvement of disgust in anxiety disorders (particularly phobias and obsessive compulsive disorders) was signaled by special issues devoted to disgust in the Journal of Anxiety Disorders (McKay, 2002) and the Journal of Behavior Therapy and Experimental Psychiatry (Olatunji & McKay, 2006).

We recently coded all 139 abstracts in the PsycInfo database that mentioned disgust in the title, abstract, or key phrase from 2001-2006. Our analysis showed that the largest focus of recent work is the link between disgust and psychopathology (primarily but not entirely phobias and OCD; 37% of references), followed by neurological/neuroanatomical/neurochemical aspects of disgust (18% of references). None of the remaining topics had seven or more percent of the references. Some of the more common of these smaller categories were the psychometrics and structure of disgust, contamination and odor, dynamics of disgust (especially moment to moment changes and interactions with other emotions), moral disgust, psychophysiology, development, and expression.

The body-to-soul preadaptation theory of disgust

One reason for the recent explosion of interest in disgust may be the growing recognition that disgust is related to many social, cultural, and even spiritual issues. In 1993 we developed a theory of disgust to explain how this originally food-related emotion expanded, both in biological and in cultural evolution, to become a guardian of the body, the social order, and the soul (the body-to-soul preadaptation theory). We began with the recognition that disgust was at its core a food rejection emotion (Rozin & Fallon, 1987), but that, cross culturally, disgust elicitors come from a wide variety of domains. We suggested that foods and body products are the core disgust elicitors, the elicitors for which the brain was most directly shaped by natural selection, probably in order to avoid biological pathogens (Rozin & Fallon,1987, Rozin et al., 1993, 1997). In our view, this powerful core disgust system, which stimulates a sense of repulsion and a withdrawal from the elicitor, was preadapted for easy extension to other threatening entities, including social and moral threats. Making something disgusting means producing internalized motivation to avoid it.

What is done with feces in toilet training can be done with other things, including inappropriate sex, poor hygiene, violations of the body envelope (e.g., the stump from an amputated hand, or viscera exposed by a wound), and death. Although many of these avoidances may have some health benefits, the justification that people are aware of is often more symbolic. Large families of disgust elicitors are features that humans share with animals: eating/food, excreting, sex, soft body interiors, and death. The authors formulated this entire set of elicitors as reminders of our animal nature. In this view, humans display, in most cultures, a strong desire to be seen as qualitatively distinct from other animals, to be “more than animals.” Disgust is in the service of this desire by causing us to recoil from reminders of our animal nature.

Perhaps the most threatening characteristic that humans share with other animals is mortality, and avoidance of contact with death, either physically or mentally, seems to be central to disgust. The quintessential odor of disgust, the putrid odor, is the odor of decaying animal flesh. Our linking of disgust and death, inspired in part by Ernst Becker’s (1973) Denial of Death, paralleled the development of terror management theory (TMT) in social psychology (Greenberg, Pyszczynski, & Solomon, 1986; Solomon, Greenberg, & Pyszczynski, 1991). TMT, also rooted in Becker’s ideas, highlights the importance of commitment to cultural norms as a defense against individual mortality. Direct linkages between mortality salience and disgust have been established (Cox et al., 2006; Goldenberg et al., 2001).

Our further analysis suggested two other domains of disgust elicitors, not related to our animal nature. One is interpersonal disgust: disgust at other persons, particularly strangers and out-groups. A second is moral disgust, in which disgust is harnessed to produce offense at certain culturally determined moral violations. In terms of Shweder’s cross-cultural taxonomy of moral systems (community, autonomy, and divinity; Shweder et al., 1997), disgust seems to be the emotion linked to violations of divinity (the CAD triad hypothesis, Rozin et al., 1999b). Haidt and his colleagues have demonstrated that disgust plays a direct role in many moral judgments (Haidt, 2001; Haidt, Koller & Dias, 1993; Wheatley & Haidt, 2005). Disgust is now a part of moral psychology.

What (Else) Makes Disgust (Suddenly) so Interesting?

Disgust has a number of special properties that might account for its recent and rapid rise as an object of interdisciplinary study. It also has a few properties that ought to motivate more research in the future.

1. Convenience. Psychologists have understandably tried to bring their research into the laboratory, to establish more control and allow for experimentation. One of the challenges of emotion research is that, ethically, it is difficult to elicit strong emotions in the laboratory. In particular, it is ethically problematic to elicit fear or anger in a realistic way in the laboratory. It is relatively easy, however, to stimulate disgust in the laboratory—even in an fMRI scanner--and this can be done in ethically acceptable and ecologically valid ways. One can present real disgust elicitors, in photograph or in reality (e.g., a cockroach) and produce strong disgust in participants. We have done this using over 20 different real elicitors (Rozin et al., 1999a).

2. Contamination. Contamination is a special property of disgust elicitors; they have the power to render a good food inedible by mere brief contact (Rozin, Millman & Nemeroff, 1986). Examples of contamination seem to follow the sympathetic magical law of contagion: “Once in contact, always in contact.” Sensitivity to contagion appears to be present in all adult humans, but absent in children (see Fallon, Rozin, & Pliner, 1984; reviewed in Rozin & Nemeroff, 1990). Contamination effects, for which disgusting entities are particularly good elicitors, are of interest to researchers in judgment and decision making, because the effects are very powerful and often “irrational.

It is important to recognize that contagion effects using disgust elicitors are not directly mediated (in contemporary humans) by a fear of infection. Although individuals typically justify their rejection of a juice contacted by a cockroach in terms of health risks, their aversion is not reduced significantly if the cockroach is sterilized (Rozin et al., 1986). Contamination effects connect disgust research with work on essentialism in developmental psychology, and likewise with the study of obsessive compulsive disorder.

3. The disgust scale. The availability of a tool often stimulates research and makes what the tool measures more salient; this seems to have happened for disgust. The Disgust Scale (Haidt, McCauley, & Rozin, 1994) has become a widely used instrument, and because it was designed to investigate many subtypes of disgust, rather than providing an overall score, it has stimulated discussion of the structure of disgust, and of the relationships between subtypes of disgust and specific mental disorders (Olatunji et al., in press). (Information about the Disgust Scale is available at: www.people.virginia.edu/~jdh6n/disgustscale.html )