Cognitive and psychophysiological responses to threat stimuli : the effect of perceived proximity

Abstract

In a series of six studies, this thesis examines the effect of the perceived proximity of a threat on cognitive and psychophysiological responses.  Study 1 used a visual probe task to assess initial attentional allocation in high and low spider-fearful participants to pictures of distally and proximally perceived spiders and rabbits. However, the results did not show a significant interaction effect of fear group and stimulus proximity on attentional bias.  Study 2 involved a physiological recording task measuring startle eye blink and skin conductance responses (SCR) followed by a visual probe task, using similar stimuli and participants. The results showed that the proximal spider pictures elicited a potential startle response in the high fear group. This group also showed greater SCRs to the spider pictures in general. Study 3 involved a hybrid task that allowed for the concurrent assessments of attentional measures and physiological responses.  Although the high fear group showed potentiated startle and SCRs whilst viewing the spider pictures, there was no difference in their psychophysiological responses between the two perceived proximity conditions. The eye movement measures showed that the high fear group was more likely  than the low fear group to direct their gaze towards spiders; however this bias was not affected by the proximity manipulation. Study 4 used the same hybrid task, but involved a greater size ratio between the proximal and distal stimuli.  The startle probe results replicated the finding of Study 2, with the proximal spiders eliciting a potentiated startle response in the high fear group. However, the other measures did not differentiate between the fear groups.  Study 5 looked at behavioural action tendencies suing an Affective Simon Task. Participants in the high fear group were relatively faster to avoid and slower to approach proximal spiders compared to the low fear group. Study 6 assesses eye movement measures. The high fear group demonstrated faster initial orienting towards the proximal spiders, followed by avoidance, as reflected by the duration of gaze.

The results of these studies suggest that the psychophysiological and attentional responses elicited by proximal and distal threat are indeed different, as predicted by the various models discussed.  Distal threat elicits increased SCRs in fearful participants, but no reliable potentiated startle response or behavioural tendencies of avoidance. Proximal threat, on the other had, elicits increased SCRs and a potentiated startle response (in 2 out of 3 studies), faster initial orienting with subsequent avoidance, and the behavioural tendencies of avoidance in fearful participants. These results provide some support for predictions from both the cognitive models of anxiety and the models based on animal behaviours.

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