Novelty and conflict in the categorization of complex stimuli.

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.