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Measuring change blindness in specific phobia: A replication




Wilamowska, Zofia

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People often fail to notice changes in visual scenes, a phenomenon know as --Y΄change blindness.‘ At least some change blindness results because relevant changes in scenes occur during eye movements. The flicker paradigm was developed by Rensink, O’Regan, and Clark (1997) as a way to study blindness to change during eye movements. In the flicker paradigm brief blank-space intervals are interposed between repeated presentations of scene pairs in order to mimic the eye movements. The second scene of each pair is changed at some point and the time or trials needed to detect that the scene has changed is recorded. Wheeler (2003) used the flicker task to study a possible relation between change blindness and fear. Half of his participants were snake phobic, half were not. Half of the image pairs he used included a snake, half did not. Half of the scene changes were made to central-interest aspects of the scene, half were made to marginal-interest areas. Wheeler found that snake-fearful participants took longer than did controls to detect changes within the marginal areas of scene pairs that did not include a snake. Wheeler’s result was clearly significant but not predicted. Therefore a procedural replication was undertaken that used twice the number of participants used by Wheeler. Controls and snake-phobic participants completed Wheeler’s (2003) flicker task. A 2 (Stimuli: neutral vs. feared) x 2 (Locations of change: central interest vs. marginal interest) x 2 (Groups: snake phobic vs. non snake-phobic) repeated measures ANOVA was performed on the number of repetitions required to detect changes between stimulus pairs. The snake phobic participants required fewer repetitions to detect changes than did the non-fearful participants; fewer cycles were required for detecting changes in the feared versus the neutral stimuli; and fewer repetitions were required to detect changes in central locations of interest than in marginal locations of interest. A three-way interaction between Stimuli x Locations of change x Groups was significant, F(1, 22) = 7.148, p = .014. Snake phobics required more repetitions than did control participants to detect changes in the marginal interest areas of neutral stimulus pairs. A plausible explanation of the three-way interaction is that phobics were relatively unable to disengage from a visual search for feared stimuli (Fox, 1993, 1994, 2001, and 2002). According to Fox’s disengagement theory, once a feared stimulus is attended to, a phobic individual is not able to quickly stop attending to it. In the present study, phobics may have still been processing the feared stimulus pairs during the presentation of the neutral stimulus pairs, and were delayed in detection of changes in the marginal interest areas of the neutral stimulus pairs.