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Hyejin Yang, Gregory J. Zelinsky; Evidence for guidance in categorical visual search. Journal of Vision 2006;6(6):449. doi: 10.1167/6.6.449.
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When we search for a pen or a paper to jot down a note, the targets in these tasks are not specific visual patterns but rather categorically defined classes of objects. Although search is clearly guided by the visual features of specifically defined targets, it is not known whether search is similarly guided by the visual features defining an object class. We addressed this question by having subjects do two versions of an identical teddy-bear search task; one with a visually non-specific categorically defined target (e.g., “find the teddy-bear”) and the other with a specifically defined visual target (i.e., subjects were shown a target preview). Guidance was defined by the proportion of initial saccades directed to the target and by the cumulative probability of target fixation. As expected, we found evidence for target-specific guidance in both of these measures. More importantly, we also found evidence for guidance to categorically defined targets. Although categorical guidance was not as pronounced as target-specific guidance, subjects searching for the teddy-bear object class preferentially directed their initial saccades to teddy-bear targets and fixated these targets sooner than what would be expected from chance. In follow-up experiments we varied the repetition of specific targets and distractors in a categorical teddy-bear search task to determine how the availability of specific visual templates affects categorical search behavior. The data from these experiments suggest that subjects were forming non-specific visual templates for object classes and using these class-defining features to guide their categorical search.
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