PET evidence for multiple strategies of categorization.

It is widely held that people use multiple strategies to categorize their experiences in the world. We conducted a pair of neuroimaging experiments to identify the neural correlates of two of these strategies--rule application and exemplar similarity. Participants were instructed to perform either a rule- or an exemplar-based categorization task while changes in cerebral blood flow were measured using positron emission tomography. Patterns of neural activity were consistent with the predictions of cognitive models of rule-versus exemplar-based categorization and with existing neuroscience data. The identification of strategy-specific neural patterns offers future researchers a diagnostic tool for assessing strategy use in other situations.