یک تظاهرات تجربی که ترس، اما نه تنفر، با بازگشت ترس در هراسها همراه است

It has been suggested that disgust, rather than anxiety, may be important in some phobias. Correlational studies have been ambiguous, indicating either that disgust increases phobic anxiety or that phobic anxiety potentiates disgust. In the experimental study reported here, disgust and phobic anxiety were manipulated in the context of habituation to phobic stimuli. Spider fearful participants were randomly allocated to conditions in which neutral, disgusting, and phobic anxiety provoking stimuli were introduced into a video-based spider phobic habituation sequence. Exposure to the phobic stimulus resulted in a return of self-reported fear and disgust levels. However, exposure to disgusting stimulus increased disgust levels, but not anxiety levels. Results are most consistent with the hypothesis that fear enhances the disgust response in phobias, but that disgust alone does not enhance the fear response. Previously observed links between disgust and spider phobia may be a consequence of fear enhancing disgust.

The leading theory in specific phobias remains Mowrer's two-process theory, which sought to explain the resistance of phobic responding to extinction as a consequence of natural repetition. Mowrer (1947) suggested that phobic fears are acquired through classical conditioning, which fails to extinguish because of the development of avoidance responses. Such avoidance is in turn maintained by operant conditioning, specifically negative reinforcement contingent on the avoidance and escape responses characteristic of phobias. More recently, the clinical observation that some phobics report high levels of disgust associated with exposure to phobic stimuli (e.g., in vomit phobia and some small animal phobias such as rats) led some to question the role of anxiety and suggest that disgust may be the primary emotion. These ideas were linked to the potential evolutionary significance of disgust in disease avoidance (Matchett & Davey, 1991). It is suggested that risk of disease or contamination, rather than threat of physical danger, leads humans to experience “phobic disgust” in the presence of particular harmless animals. The adaptive significance of the disgust response may be the prevention of contact with objects that might transmit infection or disease (Rozin & Fallon, 1987). Such an evolutionary perspective also suggests that disgust being resistant to extinction would have a protective function. This is because the occurrence of disease transmission operates on a protracted time scale, making the perception of contingent relationships between a source of infection and actual infection very unlikely. Initial research focussed on the issue of the association between disgust sensitivity and phobic responding. Disgust sensitivity has been found to correlate with fear of certain types of animal in a study carried out on non-phobic participants by Matchett and Davey (1991). Mulkens, De Jong, and Merckelbach (1996), using a behavioural test (reluctance to eat a biscuit over which a spider had crawled) found that spider phobics have higher disgust sensitivity than non-phobics. However, it has been suggested ( Thorpe & Salkovskis, 1998) that avoidance of the biscuit may have been due to an amplification of the normal disgust response caused by its association with the phobic object rather than a specifically causal link between disgust sensitivity and phobic responding. Spider fear in non-phobic participants, as measured by the Spider Phobia Questionnaire, was found to be associated with scores on the Animal subscale of the Rozin Disgust Sensitivity Scale, and with scores on the Disgust Questionnaire ( De Jong & Merckelbach, 1998). Other studies suggest a less prominent role for disgust in specific phobias. Thorpe and Salkovskis (1998) found little evidence for disgust as a causal or maintaining factor in specific phobias, with the disgust associated with the phobic object appearing to have different constituents to the disgust associated with non-phobic objects. Mulkens et al. (1996) found that spider phobics did not differ from non-phobics in behavioural tasks testing general repugnance to dirty objects rather than spider-related repugnance, so that there was no evidence of differences in disgust responses and sensitivity. It may be that where increased disgust sensitivity is found this is an effect rather than a cause of the specific phobia. Tolin, Lohr, Sawchuk, and Thomas (1997) found that the majority of spider phobics experience primarily fear (rather than disgust) when viewing phobic stimuli. Contrary to the disease-avoidance model, Thorpe and Salkovskis (1997) found that those being treated for spider phobia most commonly cited ‘legs,’ rather than dirt or disease, as being the most disgusting thing about spiders. Attributes relevant to fear, rather than disgust, were most often cited when listing the characteristics of spiders. Thorpe and Salkovskis (1998) found that spider phobics’ feelings of disgust related to spiders are allied to ideas of danger, fear and avoidance, rather than ideas of disease, sickness or contamination. There has only been one previous experimental investigation of the link between disgust and fear. In Webb and Davey (1992), unselected student participants rated their fear of various types of animals before and after watching videos depicting violent, disgusting or neutral scenes. Results suggested that those who had watched the disgusting material increased the rating of fear of animals categorised as Hi Fear/Lo Predatory (e.g., spider, snake, cockroach) and as Hi Revulsion (e.g., caterpillar, maggot, cockroach (sic)). Webb et al. concluded that manipulating disgust levels affected anxiety responses to certain animals such as spiders, and suggested that this effect was indicative of a causal link between disgust and fear ratings in an unselected sample. There are therefore two competing views on the link between disgust and phobic responding. Certain authors (e.g., Davey, 1992; De Jong, Peters, & Vanderhallen, 2002; Matchett & Davey, 1991) propose that disgust is a causal factor in phobic anxiety, with certain animals eliciting phobic responses because of their revulsive and contaminant properties. Disgust would, in this context, represent a causal factor. However, other authors (e.g., Thorpe and Salkovskis, 1995 and Thorpe and Salkovskis, 1998) propose that fear amplifies pre-existing general disgust tendencies, with disgust responses increasing when stimuli normally associated with disgust become the focus of phobic anxiety. According to this view, disgust reactions may represent vulnerability but not a causal factor. It is of course extremely difficult to investigate causal influences in specific phobias, and particularly so using experimental methodology. Experimental studies such as that reported here therefore have to rely upon methodologies more closely related to the maintenance and exacerbation of pre-existing fear. Without such experimental studies, it will not be possible to advance our understanding of the key relationships beyond the correlational level. The study reported here is a first stage in the development of an experimental methodology. The study aims to examine the relative impact of acutely increasing fear or disgust in spider phobics as part of an experimental procedure with strong ecological validity. This was done in the context of a habituation series in which participants watched a video of a moving spider whilst rating disgust and anxiety. It was hypothesised that induction of phobic anxiety would potentiate anxious and disgust responses, but that a disgust induction would not increase anxiety.