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Rachel Wu, Jared Band, Rebecca Nako, Gaia Scerif, Richard Aslin; The effect of perceptual narrowing on category-based visual search: an ERP study. Journal of Vision 2014;14(10):1070. doi: https://doi.org/10.1167/14.10.1070.
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Visual search guided by attentional templates specifying target-defining features (e.g., your car keys) is more efficient than category search (e.g., any type of keys). However, some categories of objects may be processed more efficiently because individual exemplars are not discriminable due to the absence of expertise (i.e., perceptual narrowing). With adults, we measured the N2pc component (an early ERP marker of target selection) in a visual search experiment where targets were defined as either one item (i.e., a specific monkey face) or categorically (i.e., any monkey face) among distractors from a different category (i.e., other animal faces). In addition to target-matching trials, foil trials presented participants with a category-matching non-target (i.e., Face 2) while participants were asked to search for Face 1. If foil trials elicited the N2pc component, it would indicate that participants used a category-based search strategy (i.e., find any monkey face) prior to searching for a specific monkey face. The N2pc was largest during search for a single monkey face, demonstrating that target selection is most efficient when it is guided by a feature-specific template. There was a smaller N2pc on category search trials, indicating that search for any monkey face was less efficient than search for a specific monkey face. Finally, a small but reliable N2pc was present on foil trials, suggesting that participants did initially consider non-target monkey faces as targets prior to indicating target absence with a behavioral response. Our results are threefold: First, category-based search can operate at early visual stages. Second, category-matching non-targets attract attention, suggesting that category search in this case precedes identity search (i.e., locating any monkey face prior to locating a specific monkey face). Third, despite this search strategy (due to perceptual narrowing), the N2pc at the category level is still less efficient than feature-guided search.
Meeting abstract presented at VSS 2014
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