We manipulated categorical typicality and the presence of conflicting information as participants categorized multifeatured artificial animals. In Experiment 1, rule-irrelevant features were correlated with particular categories during training. In the test phase, participants applied a one-dimensional rule to stimuli with rule-irrelevant features that were category-congruent, category-incongruent, or novel. Category-incongruent and novel features delayed RT and P3 latency, but had no effect on the N2. Experiment 2 used a two-dimensional rule to create conflict between rule-relevant features. Conflict resulted in prolonged RTs and larger amplitudes of a prefrontal positive component, but had no impact on the N2. Stimuli with novel features did elicit a larger N2 than those with frequent features. These results suggest limitations on the generality of the N2′s sensitivity to conflicting information while confirming its sensitivity to attended visual novelty.
KeywordsN2; N200; Event-related potentials; Conflict; Rule; P300 latencyThe study of perceptual categorization has long been concerned with the effects of typicality, selective attention to an object's features, and the need to suppress the influence of features suggesting the incorrect category (Allen & Brooks, 1991;Nosofsky, 1986;Regehr & Brooks, 1993;Rosch & Mervis, 1975;Smith, Patalano, & Jonides, 1998). The current study focuses on the influences of typicality and conflicting information during visual categorization and explores the degree to which ERP measures will reflect and perhaps help tease apart these two factors.For natural categories, typical exemplars (e.g., SPARROWas a type of bird) elicit faster verification responses than atypical exemplars (e.g., CHICKEN). Typicality can be thought of as the extent to which an item overlaps with the central tendency of a category or the amount of positive evidence supporting the assignment of an item to a category. Category verification times are also influenced by the presence of conflicting information or the amount of evidence suggesting assignment to the wrong category. For natural categories, this is most easily seen in prolonged RTs to reject items that share features with a target category but are not in fact members (as in rejecting BATas a type of bird; Heinze, Münte, & Kutas, 1998;McCloskey & Glucksberg, 1979). Despite these examples, it is fairly difficult to tease apart the influences of typicality and conflicting information, particularly for trials that receive the same response. For instance, as compared to sparrows, chickens are poor birds because they lack some common Address reprint requests to: Jonathan Folstein, Psychology Department, Vanderbilt University, 301 Wilson Hall, 111 21st Avenue South, Nashville, TN 37203, USA. E-mail: jonathan.r.folstein@vanderbilt.edu.
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Author ManuscriptPsychophysiology. Author manuscript; available in PMC 2009 April 1.
Published in final edited form as:Psychophysiology. 2008 April ; 45(3): 467-479.
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