Electrophysiological correlates of category induction: PSW amplitude as an index of identifying shared attributes.

Event-related potentials (ERPs) were recorded from 15 healthy adults while they performed a category induction task. Two geometric figures characterized by three dimensions (color, shape, and stripe orientation) were presented simultaneously to subjects who were asked to identify their shared attributes. Pairs of figures sharing common attributes composed the category induction condition and pairs of identical figures composed the non-induction condition. It was hypothesized that non-induction only involves abstracting shared attributes from one stimulus, but category induction involves identifying shared attributes by comparing the two stimuli. The ERP waves elicited by induction and non-induction did not differ on N1, P2 and P3b components, but larger frontal N2 and smaller central-parietal PSW components were elicited by category induction. These results suggest that the processing of category induction is reflected in the PSW 400-650 ms post-stimulus.