Harald Merckelbach

The etiology of specific phobias: A review

Abstract The present article summarizes theory and data about symptomatology, epidemiology, and etiology of specific phobias. Additionally, the cognitive mechanisms involved in specific phobias are briefly discussed. By and large, the general pattern behind the development of specific phobias can be summarized as follows. Specific fears are highly prevalent among young children. In most children, these fears represent transitory phenomena. However, in a small sub-group of children, specific fears become chronic due to classical conditioning, modelling, and/or negative information transmission. Once a specific phobia has developed, it may be maintained by cognitive biases (i.e., attentional bias, covariation bias, and reasoning bias). Though specific phobias form a heterogeneous class of disorders, this pattern appears to be a good approximation. Nevertheless, several questions remain. For example, there is no ready explanation for the fact that specific phobias are more often diagnosed in women than in men. Similarly, it is not clear to what extent the nonrandom distribution of phobias can be interpreted in terms of cultural factors. Resolving these issues is not only important in its own right, but may have considerable heuristic value for our understanding of other anxiety disorders.

PATHWAYS TO SPIDER PHOBIA

Using a revised version of the Phobic Origin Questionnaire (POQ; Ost, L. G. & Hugdahl, K. Behaviour Research and Therapy, 19, 439-477; 1981), the present study examined whether conditioning experiences, modeling experiences, and/or informational learning experiences were more often reported by spider phobics (n = 41) than by non-fearful controls (n = 30). The two groups did not differ with regard to the overall frequency of conditioning or modeling events. Remarkably, the frequency of informational learning was higher among non-fearful Ss than among phobics. Although the limitations inherent to the retrospective nature of the present study should be borne in mind, the data suggest that, at least in spider phobics, conditioning events, modeling experiences, and/or informational learning do not necessarily give rise to phobic fears.

Conditioning experiences in spider phobics

Using the Phobic Origin Questionnaire (Ost, L. G. & Hugdahl, K. Behaviour Research and Therapy, 19, 439-477, 1981), the present study examined the extent to which severe spider phobics (N = 42) attributed their phobia to conditioning experiences, modeling experiences and/or informational learning experiences. Modeling was most often reported (71%), followed by conditioning (57%), and informational learning experiences (45%). It was also found that patients with a conditioning background reported less extreme cognitive symptoms when confronted with the phobic stimulus than patients with an indirect mode of acquisition (modeling and/or informational learning).

Hemisphere Preference, Phobia, and Depression

The present study was undertaken in order to examine whether depression and anxiety are related to preference for a right hemisphere mode of thinking. On the basis of a paper-and-pencil test presumably measuring hemisphere preference (Preference Test; Zenhausern, 1978), normal subjects (N = 75) were assigned to a group characterized by a left hemisphere thinking style, a group characterized by a right hemisphere thinking style and a group with mixed tendencies (left and right hemisphere tendencies). Additionally, subjects completed the Fear Questionnaire and the Depression Symptom Inventory. It was found that subjects with a right hemisphere thinking style reported more depressive and fear symptoms than subjects with a left hemisphere thinking style. This finding is in line with theories which assume that the right hemisphere is characterized by a negative, dysphoric emotional tendency.

HEMISPHERE PREFERENCE, ANXIETY, AND COVARIATION BIAS

In Study I, normal subjects (N = 70) completed the Preference Test (PT), the Spielberger State-Trait Anxiety Inventory, and the Anxiety Sensitivity Index. Subjects with a preference for a right hemisphere thinking style (as indexed by PT) were found to have higher state anxiety and anxiety sensitivity scores than subjects with a left hemisphere thinking style. This finding is in line with the suggestion that the right hemisphere is involved in the development and maintenance of anxiety. n nStudy II explored whether the relationship between right hemisphere preference and anxiety may result from the different cognitive characteristics that are attributed to the two hemispheres. It might well be that cognitive biases that are thought to maintain or exaggerate anxiety states (e.g. covariation bias), emerge from a right hemisphere mode of information processing. Therefore, it was investigated whether covariation bias is linked to right hemisphere preference. Subjects were exposed to a series of slides comprising pictures of spiders, weapons, and flowers. Slides were randomly paired with either a shock, a tone or nothing. Aposteriori, subjects indicated the contingencies of each stimulus/outcome combination. Data confirmed that anxiety was related to covariation bias. However, the hypothesis that cognitive biases are linked to a right hemisphere style of thinking was only partially sustained.

Classical Conditioning: Still Going Strong

This paper summarizes developments in the field of classical conditioning. Attention is paid to four common misconceptions of what is classical conditioning. First, classical conditioning does not ensue as a simple result of temporal pairing of conditioned and unconditioned stimuli. Rather, conditioned reacting occurs if and to the degree that the subject is able to predict the occurrence of one stimulus from the presence of another one. Second, what is learned during classical conditioning is not necessarily a response to a cue, but rather a probabilistic relationship between various stimuli. Third, classical conditioning is not only manifested in responses mediated by the autonomic nervous system, but also in immunological parameters, in motoric behaviour and in evaluative judgments. Fourth, the nature of the conditioned and the unconditioned stimulus is (often) not a matter of indifference: particular combinations of CS and US produce more powerful conditioning effects than do other combinations. In the second part of the paper, the potential relevance of these developments is illustrated. Discussions are included about anxiety, addictions and food aversions/conditioned nausea.