Can we attend to large and small at the same time?
Evidence from several sources suggests that visual attention is tuned to stimulus scale. This tuning impairs performance when the observer must attend to more than one scale at a time. In experiments originally designed to measure the bandwidth of attention to stimulus scale, we have found tasks in which observers show no attentional tuning for scale. In separate blocks, observers located or identified targets in arrays of elements, either numbers in arrays of letters or static squares in arrays of flashing squares. Each display contained two arrays, either of the same scale or of different scales. The accuracy of locating the target element was lower in mixed-scale than in single-scale displays, but the accuracy of identifying the target was unaffected by a mixing of scales within the same display. This holds for both high-level discriminations--numbers vs letters--and low-level discriminations--static vs flashing. Thus, at least for identifying, one can attend to large and small at the same time. The difference in bandwidth between "what" and "where" implies that stimulus identification is not dependent on prior localization.
Farell
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Institute for Sensory Research, Syracuse University, NY 13244-5290.
Pelli
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DG
D001288:Attention / Q000502:physiology*; D004192:Discrimination, Psychological / Q000502:physiology; D006801:Humans; D010364:Pattern Recognition, Visual; D012858:Size Perception / Q000502:physiology*; D013028:Space Perception / Q000502:physiology