Interest in the emotion of disgust has grown rapidly in recent years, in part because disgust sensitivity is thought to play a role in anxiety disorders like obsessive compulsive disorder (OCD). Disgust sensitivity is usually measured using The Disgust Scale, developed by Haidt et al in 1994. However, while use of this scale has grown to include studies on clinical, non-clinical and cross-cultural samples, a comprehensive examination of its psychometric properties has, until now, not been conducted.

Bunmi Olatunji and colleagues administered the 32-item Disgust Scale to 655 undergraduate students. Sixteen of the scale's items are statements like "It would bother me tremendously to touch a dead body" requiring a true-false response, while the remaining 16 items such as "You see maggots on a piece of meat in an outdoor garbage pail", require a response on a three point scale from finding the experience "not disgusting at all" to "very disgusting".  For comparison, the students also completed an alternative 30-item scale – the Disgust Emotion Scale devised by Kleinknecht et al in 1997.

Analysis revealed five problematic items were not normally distributed and failed to distinguish between high and low disgust sensitive students based on their scores on the comparison scale. Three of these items were related to sex, suggesting sociomoral issues may be better tapped by a separate scale.

Previously the Disgust Scale has been considered to tap 8 domains of disgust: food, animals, body products, body envelope violations, death, sex, hygiene, and sympathetic magic (related to infection and contamination). However, factor analysis showed that the Disgust Scale has just two clear factors "Core Disgust" (a sense of offensiveness and threat of disease) and "Animal Reminder Disgust" (aversion to stimuli that remind one of the animal origins of humans) as well as a weaker, third factor "Contamination-based Disgust" (perceived threat of transmission of a contagion).

A second study, using a revised 27-item version of the Disgust Scale, with the problematic items removed, was given to 993 students, who also completed the Obsessive Compulsive Inventory. These results confirmed the three-factor model provided a good fit to the data and identified a further two items that could be removed because of redundancy. Moreover, preliminary construct validity for the three factors was established, with Core Disgust and Contamination-based Disgust, but not Animal Reminder Disgust, predicting obsessive compulsive symptoms.

Next, a 25-item version of the Disgust Scale was administered to 215 students and compared with their scores on the original 32-item version. The new version showed good internal consistency and predicted scores on the original version. In other words, the new version has improved psychometric properties but a more parsimonious structure compared with the original instrument.

Finally, the researchers gave the new 25-item Disgust Scale to 56 patients with OCD. Compared with healthy controls and OCD patients without a washing compulsion, OCD washers recorded higher scores on the Core Disgust and Contamination-based Disgust factors of The Disgust scale, but not on the Animal Reminder Disgust factor.

The researchers concluded "The psychometric evaluation and refinement of the revised Disgust Scale represents an important step toward the development of a psychometrically sound measure of disgust sensitivity." However, they added that further improvements still need to be made. For example, half of the scale's items which require a true/false response don't even feature the word "disgust". Moreover, many of the scale's items are almost identical to items from OCD symptom scales, which could be inflating correlations between disgust sensitivity and measures of OCD symptomatology.

References:

Olatunji, B.O., Williams, N.L., Tolin, D.F., Abramowitz, J.S., Sawchuk, C.N., Lohr, J.M. & Elwood, L.S. (2007). The Disgust Scale: Item analysis, factor structure and suggestions for refinement. Psychological Assessment, 19, 281-297. http://dx.doi.org/10.1037/1040-3590.19.3.281

Kleinknecht, R.A., Kleinknecht, E.E. & Thorndike, R.M. (1997). The role of disgust and fear in blood and injection-related fainting symptoms: A structure equation model. Behaviour Research and Therapy, 35, 1075-1087. http://dx.doi.org/10.1016/S0005-7967(97)80002-2

Haidt, J., McCauley, C. & Rozin, P. (2004). Individual differences in sensitivity to disgust: A scale sampling seven domains of disgust elicitors. Personality and Individual Differences, 16, 701-713. http://dx.doi.org/10.1016/0191-8869(94)90212-7

Weblinks:

People sensitive to disgust are more likely to hold right-wing views (from the BPS Research Digest)

Reason and the Yuk factor (From The Psychologist)

Moral psychology: the depths of disgust (from Nature, subscription required)