Spider phobia

Abstract

After reading vignettes, a group of spider-phobic girls (n=18) and a group of nonphobic girls (n=18) rated the subjective probability of spiders entering their private living space, their tendency to approach and make physical contact, and the subjective probability of spiders doing physical harm. In addition, they indicated their eagerness to eat a favorite food item before as well as after it had been shortly contacted by spiders. In support of the idea that spider phobia results from the convergence of spiders’ disgusting properties and the subjective probability of involuntary contact, phobic girls reported relatively high ratings concerning: (a) the probability of spiders entering their room; (b) spiders’ tendency to approach and make physical contact; and (c) spiders’ disgust-evoking status. Finally, regression analysis indicated that spiders’ disgust-evoking status is the single best predictor of spider phobia, whereas the independent contribution of the perceived probability of spiders doing physical harm was found to be negligible. All in all, the present findings strongly support the idea that spider phobia essentially reflects a fear of physical contact with a disgusting stimulus.

Introduction

Fear of spiders is very common in nonphobic (e.g., Davey, 1992) and phobic individuals (e.g., Marks, 1987). Spider phobia is characterized by an early age of onset, and adult spider phobia is generally viewed as a typical childhood fear that has persisted and survived adolescence (e.g., Merckelbach, de Jong, Muris, & van den Hout, 1996). Even though serious interference with daily life is evident only in a minority of individuals, it still belongs to one of the most prevalent anxiety disorders (American Psychiatric Association APA, 1994, Robins and Regier, 1991).

In apparent contrast with the efficacy of the available treatments (e.g., Öst, 1989), the underlying mechanisms or causes of spider phobia remain a matter of debate. Virtually all recent psychology textbooks explain the etiology of spider phobia in terms of predator-avoidance processes (e.g., Gleitman et al., 1999, Oltmanns and Emery, 1998). Yet, there are several observations that are difficult to reconcile with a predator-defense explanation of spider phobia. First, only a very small minority of current spiders is potentially dangerous to human beings (Renner, 1990), and there is little reason to suspect that this was any different in our prehistoric past. Relatedly, spider-phobic individuals have extreme difficulty in articulating what they actually fear (“they are just creepy animals”). Furthermore, common spider fear covaries with fears of animals that are nearly universally considered disgusting rather than harmful per se, such as maggots and snails (e.g., Davey, 1992). This covariation suggests a common underlying factor, and predator avoidance does not seem to be a particularly convincing candidate for that communality.

To reconcile these apparent inconsistencies, it has been suggested that the core feature of spider phobia may be fear of physical contact with a disgusting stimulus rather than fear of being attacked and getting physically harmed (Davey, 1994). Such a disgust conceptualization of spider fear may also explain the suggestive parallel between age of onset of spider phobia and age at which children start to display disgust responses (Rozin, Hammer, Oster, Horowitz, & Marmora, 1986). Furthermore, it may explain the curious observation that spider-phobic individuals have difficulty in articulating what they fear, as a key feature of disgusting objects is that they are intrinsically offensive (Rozin & Fallon, 1987). Finally, a disgust conceptualization of spider phobia may explain the finding that only a minority of spider phobics can recall an aversive conditioning event as the starting point for the development of their phobia (e.g., Merckelbach, Arntz, & de Jong, 1991).

If, indeed, disgust is an important feature of spider phobia, spiders should also share the striking feature of any disgusting substance: namely, that they can render a perfectly good food item inedible by brief contact (even when there is no detectable trace of the offensive item) (Rozin & Fallon, 1987). In support of this, research demonstrated that most spider phobics refused to eat (part of) a preferred cookie after it had been in short contact with a live spider, whereas the motivation to eat the cookie was largely unaffected in the nonphobic control group (Mulkens, de Jong, & Merckelbach, 1996). The suggestion that the spider’s disgusting properties play an important role in fear of spiders is further supported by the finding that spider-phobic individuals typically report their phobic stimulus (i.e., spider) as their most disgusting item (Thorpe & Salkovskis, 1998) and, relatedly, respond with disgust as well as fear to pictures of spiders (Tolin, Lohr, Sawchuk, & Lee, 1997). Meanwhile, the disgust interpretation of spider phobia also raises an important question that needs to be addressed.

If disgust is the core feature of spider phobia, why does fear of maggots, snails, or other disgusting objects only seldom reach the phobic range? One explanation might be that the probability of involuntary physical contact is much smaller for maggots and snails than for spiders (Andrea, 1996). That is, spiders but not maggots and snails often enter an individual’s private territory (e.g., bedroom). The fact that spiders can move quickly is likely to further inflate the perceived probability of involuntary physical contact. Following this, spider phobia results from the convergence of two orthogonal dimensions: (1) spider’s disgust-evoking properties, and (2) the perceived likelihood of physical contact. Consistent with this suggestion, Davey (1993) found that disgust sensitivity added to an individual’s fear ratings of a novel animal stimulus when it was modulated in an interactive fashion by beliefs about being physically contacted by the animal.

The present study was designed to investigate further the tenability of the idea that spider phobia essentially reflects a fear of involuntary physical contact with a disgusting stimulus. Therefore, we invited a group of spider-phobic girls who applied for treatment in our ongoing Spider Phobia Project and a group of nonfearful controls to participate in the current study. First, we tested the presupposition that, in general, people consider it quite probable that spiders will enter their private living space (e.g., bedroom). Relatedly, we explored whether the perceived probability would be higher in spider-phobic compared to nonphobic girls. Second, we investigated the subjective probability of spiders approaching the individuals once a spider entered their private territory (e.g., bedroom) and the subjective probability of the spider making direct physical contact with them (e.g., cross their body). To investigate the role of predator-defense type beliefs, we also asked the participants to rate the probability of the spider doing actual physical harm (e.g., will bite), once it entered their room.

To test the disgust-evoking status of spiders, we used an in vitro variant of the cookie test (e.g., de Jong, Andrea, & Muris, 1997). In a similar vein, we investigated the disgusting properties of flies and maggots (cf. Rozin, Fallon, & Mandell, 1984). Flies were selected because they share the threat of physical contact dimension with spiders (i.e., flies frequently enter a person’s private territory and people are often physically contacted by flies). Meanwhile, people seldom report a fear of flies. Thus if, indeed, an interaction between disgust and threat of physical contact results in small animal fears, flies should possess only minor disgusting properties. Therefore, the present interaction hypothesis predicts that the motivation to eat a preferred food item will only be marginally influenced by being contacted by a fly.

Maggots were selected because they share the alleged disgust dimension of spiders. If the disgust conceptualization of spider phobia is correct, one would predict that for spider-phobic but not for nonfearful individuals, the disgust-evoking status of spiders (and thus their negative influence on the edibility of food items after short contact) would come close to that of maggots.