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Abstract:
We previously developped stimuli allowing parametric control over the percept of animacy evoked by the movements of a single object, without contribution from spatial arrangement, shape or structure of the object (Schultz and Dopjans, 2008 Perception 35 ECVP Supplement, 154). As observers tend to follow the stimulus with their eyes while performing animacy judgments, we quantified these eye movements in the present study (Experiment 1). In Experiment 2, we tested the importance of eye movements and attention for task performance by forcing subjects to fixate while judging animacy. In Experiment 3, attentional resources were further reduced by asking subjects to perform a secondary task at fixation while judging animacy. Experiment 1 showed that the distance between eye fixations and the stimulus increased with changes in animacy, compatible with a greater difficulty in following animate-looking stimuli. Combined results across experiments show that the strength of the changes in percept tends to be reduced with fixed gaze and is significantly decreased in the dual-task setting. In the latter, the greatest disruption in stimulus processing appears to result from detecting and reporting the fixation targets rather than just splitting attentional resources. These results suggest that at least partially sustained attention is required for animacy judgments about our single moving dot stimulus.