Disgust is a feeling, a sensation that we all know. Suddenly finding that there are remnants of a dog’s faeces on the soles of your shoes can evoke strong disgust; and if you discover them in a social situation, you may add a good portion of shame to that. Some food, beloved by almost all, can be extremely repulsive to a person. Pregnant women can develop peculiar desires for odd combinations of edible stuff, whereas they can experience extreme disgust for things they always liked, up to the point of having to vomit. De gustibus non est disputandum, the ancient Romans said: it’s no use to fight over taste; and that applies to my latter examples too.
Disgust is a feeling that may be present in various forms of OCD, most notably in contamination fears/washing compulsions. But hoarders may have it too: when one has ten or more large garbage sacks in one’s kitchen, filled to the brim with rotten food residues, one can experience a terrible disgust when arriving home; not per se because those bags smell ugly, but because fear and repulsion of the whole situation can make one turn around and flee one’s house, to be anywhere else but home.
In this chapter I would like to go through some aspects of that basic human emotion called disgust; mainly in its relation to contamination fears. Rachman (2006) provided a nice, compehensive definition of what contamination fear is:
CF is the intense and persisting feeling of having been polluted, dirtied, or infected, or endangered as a result of contact, direct or indirect, with an item/place/person perceived to be soiled, impure, dirty, infectious, or harmful.
Phew… this Rachman person wanted to cover all grounds, don’t you think?
We know that contamination fears are linked to OCD in the narrow sense, although they may be re-classified on some theoretical grounds and eventually become a separate type of disorder (about which later). CF can also be connected to extreme anxiety about one’s health, and to post-traumatic stress disorder (PTSD) that is the result of sexual assault.
The functional role of disgust in contamination fears is to avoid contact with harmful substances, either touching those or ingesting them. It is not hard to understand how important this is for evolution. We learn in our upbringing that we must not come close to certain stuff, nor touch it, or put it into our mouths. But we do not enter this world without safety systems to begin with; there are innate mechanisms that make us shy away from things we don’t like ‘on instinct’. Perhaps the smell of rotten eggs is an example; it is the smell of hydrogen sulphide (H2S), a toxic gas.
It has been known for quite some years now that in contamination fears, the processing of emotions of disgust is tightly associated with a greater level of activity in a brain area that is our special center of ‘disgust perception’, and this region is called the insula (which is Latin for ‘island’). It is notably the anterior insula, or the frontal part of the insula, that shows increased activation here (see: Calder et al, 2007). Now, it could be that this higher activity in the digust-specific brain area is not related to CF obsessions in themselves, but rather to very high levels of general anxiety and fear-related traits at large. Well, this potential confounding factor was researched and clarified: that was not the case. There is good evidence for a special role of disgust in contamination fears.
The story up until now refers to what we call: the domain of affect. This is a very direct experience of emotion, not brought about by intermediate ‘considerations’, more or less conscious reflexive processes. Cisler et al (2010) pondered the question whether also more indirect expressions of unease and repulsion are possible; namely in the domain of cognition. Here, an overestimation of threat can be present in CF; there may be a memory bias (CF patients have a better memory of how many clean objects were touched with a contaminated object than did healthy subjects – now isn’t that amazing?). Also, other research indicated that CF patients have considerably more problems with directing their attention away from cues they find threatening, because they are related to contamination (from now on called: delayed disengagement from disgusting stimuli).
The group of Cisler (2010) proposed their hypotheses as follows:
“disgust may be more important in mediating reactions towards objects with more apparent and direct contagion properties (e.g., normative disgust elicitors), whereas the cognitive mechanisms implicated in CF may be more important in mediating reactions towards objects that have only indirect and distal contagion probability (e.g., elevator buttons may only become contaminated if someone sick sneezes on them).”
Examples of the above: the direct way to disgust may be illustrated by objects that are perceived as ‘realistically contagious’, such as a dirty bedpan, or rotten foodstuff. The indirect way requires some ‘detour in fearful thinking’ (my phrasing); a public telephone, a keyboard in an open library, money, and elevator buttons then may be seen as potentially infectious (intermediate fear: ‘…I must touch it, but… but… someone may just have sneezed on it!’). This then is the cognitive path.
A group of non-clinical students was tested by this research group. The method to assess CF was the so-called ‘chain of contagion’ task: a simple technique, in which the dirtiest spot in the building is located, then a pencil is rubbed against that, then a second pencil is rubbed against pencil #1, then a third one against #2… up to #12.
Students had to complete a so-called ‘disgust propensity’ query, in which they answered questions related to their personal inclination towards feelings of disgust. The answers provided information about the DP for each individual. Furthermore, they did a ‘spatial queuing’ task, that provided information of everyone’s delayed disengagement from frightful and disgusting stimuli.
A higher DP successfully predicted a greater initial contamination appraisal; but a sharper decline in estimations across further degrees of removal from the contaminating source (dirtiest object, pencil #1, pencil #2, and so on).
Higher delayed disengagement from disgusting stimuli, however, uniquely predicted sustained elevations in estimations of contamination across further degrees of removal.
The authors claim: “These results suggest that DP and delayed disengagement from disgust cues explain unique and complimentary processes in contamination appraisals, which suggests the utility of incorporating the disparate affective and cognitive lines of research on CF.”