آموزش ارزیابی و عاطفی در پاسخ به محرک های ترس و نفرت انگیز در عنکبوت هراسی

The present study explores possible changes between spider phobics (N = 22) and nonphobics (N = 28) in fear, disgust, and neutral ratings of neutral expressions as a result of their pairing with spiders. No statistically significant differences were detected between pre and post fear ratings of the expressions as a result of their association with spiders. However, post disgust ratings were marginally higher than pre disgust ratings and post neutral ratings were significantly lower than pre neutral ratings. The present study also examined differences in fear and disgust responding to threat-relevant and disgust-relevant stimuli between spider phobics and nonphobics. Spider phobics reported significantly more fear and disgust than nonphobics towards threat and disgust-relevant stimuli. The relation between spider phobia and disgust responding to spiders was partially mediated by fear whereas the relation between spider phobia and disgust responding to rotting foods and body products was fully mediated by fear. Emotional responding to threat-relevant and disgust-relevant stimuli was also significantly associated with disgust sensitivity when controlling for trait anxiety. These findings support the notion that the disgust response in spider phobia is independent of fear to the extent that it is specifically bound to spiders.

Evaluative conditioning (EC) proposes that presentation of subjectively neutral material (conditioned stimuli; CS) with positive or negative stimuli (unconditioned stimuli; UCS) will change the valence of the neutral stimuli in the direction of the UCS (Levey & Martin, 1975). Evaluative responses are considered basic and primitive to all evocative UCSs (Martin & Levey, 1987), and are akin to an immediate gut reaction of preference, such as good/bad, pleasant/unpleasant; reactions that often mediate avoidance (e.g., Mulkens, de Jong, & Merckelbach, 1996). Unlike other forms of conditioning that are said to involve the learning of relations between stimuli (i.e., referential or signal learning), evaluative conditioning is said to involve a holistic form of learning where the CS and UCS become fused. Several studies have demonstrated the EC effect using various stimuli (see De Houwer, Thomas, & Baeyens, 2001 for a review) and the EC paradigm has been recently applied as an experimental means of better understanding the etiology of various anxiety-related disorders (e.g., Lascelles, Field, & Davey, 2003; Olatunji, Lohr, Sawchuk, & Westendorf, 2005). EC has also been implicated as a potential mechanism by which people learn to be fearful and disgusted (i.e., Merckelbach, de Jong, Arntz, & Schouten, 1993; Schienle, Stark, & Vaitl, 2001). The acquisition of such affective responses may then transcend into pathological emotional responses in the context of clinical disorders (Merckelbach et al., 1993). Consistent with an EC account, phobic avoidance of various stimuli capable of eliciting fear and disgust (i.e., spiders) may be a result of the evaluative properties (i.e., unpleasant) associated with those stimuli (Hekmat, 1987). Indeed, it has been suggested that spider phobics may be more vulnerable to EC processes and, as a result, benefit less from exposure treatment (e.g., Baeyens, Eelen, & van den Bergh, 1992). Although empirical evidence for this claim is limited (e.g., de Jong, Vorage, & van den Hout, 2000), it has been noted that vulnerability to EC processes in spider phobia may be related to heightened disgust responding (Merckelbach et al., 1993). Rather than the traditional fear mediated predator-defense model of animal phobias (e.g., Öhman, Dimberg, & Öst, 1985), there is accumulating evidence that spider phobia may be better characterized by a disgust-mediated disease-avoidance model (Olatunji & Sawchuk, 2005). The disease-avoidance model (e.g., Matchett & Davey, 1991) suggests that aversive, but nonpredatory, animals elicit avoidance due to concerns of contamination (disgust mediated) rather than concerns of being physically harmed (fear mediated). Fear and disgust are negative withdrawal emotions that may both contribute to the etiology and maintenance of spider phobia (Woody & Teachman, 2000). Accordingly, studies have shown that spider phobics report feelings of fear and disgust when exposed to spiders ( Sawchuk, Lohr, Tolin, Lee, & Kleinknecht, 2000; Tolin, Lohr, Sawchuk, & Lee, 1997). However, recent findings suggest that disgust may be more central than fear in spider phobia ( de Jong & Muris, 2002). For instance, Woody, McLean, and Klassen (2005) found that disgust was a stronger predictor than anxiety of avoidance of spiders. A recent study also showed that an expectancy bias towards disgust consequences, rather than fear-relevant consequences, was the single best predictor of spider fear ( van Overveld, de Jong, & Peters, 2006). Physiological data also seems to indicate disgust rather than fear in spider phobia as it has been shown that spider fearful individuals respond with greater disgust-specific facial EMG activity than non-fearful individuals when exposed to spiders ( de Jong, Peters, & Vanderhallen, 2002). In fact, it has been shown that women report more disgust than men ( Olatunji, Sawchuk, Arrindell, & Lohr, 2005). Perhaps the widely documented sex differences in the presentation of spider phobia with a higher prevalence in women compared to men ( Fredrikson, Annas, Fischer, & Wik, 1996) can be accounted for the sex differences in disgust. Elevated disgust responses observed in spider phobia are not limited to phobia-relevant stimuli, however, as studies have demonstrated that spider phobics report more aversion across a range of disgust stimuli unrelated to phobic concerns, such as rotting foods and bodily products (Sawchuk et al., 2000). It has also been shown that spider fearful participants demonstrate Stroop interference for disgust-related words (e.g., “DIRT”) that are also unrelated to phobic concerns (Barker & Robertson, 1997). This propensity to respond with disgust (i.e., disgust sensitivity) to general disgust elicitors has been implicated as a potential risk factor for spider phobia (de Jong & Merckelbach, 1998). Although several studies have implicated disgust in spider phobia (e.g., de Jong & Merckelbach, 1998; de Jong & Muris, 2002), others contend that the link between disgust and spider phobia is spurious (Thorpe & Salkovskis, 1998). Based on findings from a series of studies, Thorpe and Salkovskis, 1995 and Thorpe and Salkovskis, 1998 argue that while disgust may be associated with fear of spiders, disgust does not modulate the intensity of that fear. Although the authors found that spider phobics rated pictures of spiders as significantly more fearful and disgusting than nonphobic controls, beliefs regarding the disgust-evoking characteristics of spiders yielded minimal predictive value for self-reported phobic fear, and did not enter into regression equations predicting phobic avoidance. Furthermore, Edwards and Salkovskis (2006) found that exposure to phobic stimuli resulted in a return of fear and disgust levels among spider fearful participants. However, exposure to disgust stimuli increased disgust levels, but not fear levels suggesting that perhaps fear enhances the disgust response in spider phobia, but that disgust does not enhance the fear response. In light of the above research, debate remains in the literature as to the functional contribution of disgust to spider phobia. One account is that fear may mediate the relation between disgust responding and spider phobia (Thorpe & Salkovskis, 1998). However, disgust is a negative emotion that is strongly stimulus-bound (Woody et al., 2005) and it has been shown that spiders have a specific disgust-evoking property that is found in spider distressed and non-distressed populations that cannot be accounted for by a general negative emotional response (e.g., fear) to spiders (Vermon & Berenbaum, 2002). A more parsimonious account may be that the disgust response in spider phobia is functional to the extent that the response is bound to a threat-relevant stimulus and the disgust response in spider phobia may be illusory to the extent that it is bound to a threat-irrelevant stimulus. However, this hypothesis is yet to be directly evaluated in the literature. In the present study, EC principles are first applied to investigate how fear and disgust responding may be transferred to subjectively neutral stimuli in spider phobia. Specifically, it was predicted that spider phobics would evaluate neutral facial expressions as more fear evoking and disgusting than nonphobics after pairing the expressions with pictures of spiders. The present study also examines specificity of fear and disgust responding to threat-relevant (spiders) and disgust-relevant (rotting foods and body products) stimuli in spider phobics and nonphobics. It was predicted that spider phobics would evaluate both threat-relevant and disgust-relevant stimuli as more fearful and disgusting than nonphobics. Using a mediational model, the present study also examines whether the relation between disgust responding to threat-relevant and disgust-relevant stimuli and spider phobia is mediated by fear responding. Drawing from prior work (e.g., Thorpe & Salkovskis, 1998), it was predicted that fear responding would fully account for the relation between spider phobia and disgust responding to threat-relevant and disgust-relevant stimuli.