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Jie Huang, Ruth Rosenholtz; A unilateral field advantage in visual search and detection. Journal of Vision 2012;12(9):724. doi: 10.1167/12.9.724.
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Superior visual processing of information distributed across hemifields than in a single hemifield (bilateral field advantage) has been reported in tasks that require parallel processing (e.g. Sereno & Kosslyn, 1991). This study comprises a series of experiments exploring hemifield effects in visual search and detection.
Experiment 1 explored the hemifield effect on dual-target search, in which subjects searched for two designated targets ("T" in two different orientations) among distractors (rotated "L"s). On each trial, subjects saw a crowded display (180 msec) of twenty items (see Figure 1) and reported the presence of each of the two targets. When both present, the two targets appeared in the same hemifield (unilateral) or in opposite hemifields (bilateral). Subjects were more likely to detect two targets simultaneously on unilateral trials, suggesting a unilateral field advantage (UFA) in searching for two targets.
Experiment 2 examined if the UFA in Experiment 1 was due to the task demand of detecting two targets. Subjects performed a detection task in Experiment 2A, in which they reported the number of targets (rotated "T"s) present (0, 1 or 2), and performed an identification task in Experiment 2B, in which they identified the orientations of targets (rotated "T"s). In both tasks (see Figure 2, 3), each trial contained six items, spreading within a single hemifield (unilateral) or across hemifields (bilateral). UFA was found in detection but not in identification, and was evident only in detecting two targets. Experiment 3 replicated the findings in 2A’s detection task with 3D shaded cubes. The results suggest that UFA depends on the task demand of detecting multiple targets simultaneously.
We demonstrated a UFA in visual search and detection of more than one target. We argue that this UFA is likely due to greater integration of target signal within the same hemifield than across hemifields.
Meeting abstract presented at VSS 2012
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