Fear conditioning, the associative learning process by which a neutral conditioned stimulus acquires the capacity to elicit fear following its repeated pairing with an aversive unconditioned stimulus, features prominently in etiologic accounts of social anxiety disorder (1
). In this context, the unconditioned stimulus consists of a time-limited humiliating experience and the conditioned stimuli are those stimuli associatively linked to the unconditioned stimulus (i.e., people, places, and things) (1
). Conditioning is thought to contribute to the onset and course of social anxiety disorder by conferring anxiogenic valence to conditioned stimuli that are then capable of sustaining social anxiety beyond the presence of the time-limited unconditioned stimulus.
Theories regarding conditioning and social anxiety disorder and other anxiety disorders are not without controversy (4
). Empirical evidence for a conditioning contribution to social anxiety disorder stems largely from studies documenting high frequencies of retrospectively reported traumatic conditioning as a precipitant of the disorder (2
). However, the strength of such retrospective and subjective evidence is compromised by the often inaccurate recall of events occurring many years earlier (7
), the undue influence of leading questions regarding the origins of the phobia (8
), and evidence that fear conditioning processes can occur on an unconscious level, inaccessible to subjective experience (9
). Furthermore, many healthy individuals recall embarrassing conditioning experiences but do not go on to develop the disorder (6
), indicating that adverse social conditioning encounters are not a sufficient circumstance for the development of social anxiety disorder.
Psychophysiological paradigms in which social anxiety patients and healthy comparison subjects are classically conditioned in a laboratory setting are an alternative and promising means to further assessing the conditioning contribution to social anxiety disorder. Specifically, such paradigms do not rely on retrospective or subjective data and are capable of assessing individual differences in conditioning that may help explain why some exposed to conditioning precipitants but not others go on to develop the disorder.
To date, three such studies have been conducted in social anxiety patients (11
). These studies assessed the degree to which those with social anxiety disorder display a general proclivity toward forming aversive associations. Because of this focus on nonspecific conditionability, these studies conditioned subjects using generally aversive but socially irrelevant unconditioned stimuli such as unpleasant odors (11
) and painful pressure (13
). Results demonstrated no increase in conditioning among social anxiety subjects, whether the observed conditioned response was fear-potentiated startle (11
), skin conductance (11
), or heart rate (12
). These results suggest the absence of a general proclivity toward forming aversive associations among subjects with social anxiety disorder. Nevertheless, the involvement of a more specific proclivity among social anxiety patients to form aversive associations between socially relevant unconditioned stimuli (e.g., a humiliating experience) and co-occurring neutral conditioned stimuli (i.e., people, places, and things) remains to be tested.
In the present study, subjects with social anxiety and gender- and age-matched healthy comparison subjects underwent differential fear conditioning within a novel paradigm incorporating socially stressful unconditioned stimuli with demonstrated relevance to social anxiety disorder, such as critical facial expressions (14
) and derogatory verbal feedback (16
). Neutral facial expressions served as conditioned stimuli and were repeatedly paired with the aversive unconditioned stimulus. The conditioned response was measured as fear-potentiated startle elicited by presentation of the conditioned stimuli. Fear-potentiated startle refers to the reliable enhancement of the startle reflex when an organism is in a state of fear (18
) and is employed as an objective measurement of anxious arousal in humans (19
). The central hypothesis of our study predicted greater conditioned fear-potentiated startle in subjects with social anxiety disorder than subjects without the disorder. To our knowledge, the present study represents the first psychophysiological test of conditioning correlates of social anxiety within a paradigm employing unconditioned stimuli specifically relevant to the diagnosis of social anxiety disorder.