Searching for something familiar or novel: ERP correlates of top-down attentional selection for specific items and categories


Visual search is often guided by top-down attentional templates that specify target-defining features. But, search can also occur at the level of object categories. We measured the N2pc component, a marker of attentional target selection, in a visual search task using familiar and novel targets. Targets were defined either categorically (e.g., any letter), or at the feature level (e.g., the letter C). An N2pc was elicited during category search, in both familiar and novel contexts, indicating that even when targets are only defined at the category level, they are selected at early sensory-perceptual stages. However, the N2pc emerged earlier and was larger during feature-based search, demonstrating the superiority of attentional guidance by feature-specific templates. Moreover, category search triggered feature-specific templates, while the inverse was not the case, suggesting that higher-order search templates automatically include lower-order templates.

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