Facts, rules, and strategies in single-digit multiplication: evidence from event-related brain potentials

It has been hypothesized that zero vs. nonzero operands in single-digit multiplication problems invoke distinct solution strategies. We studied such problems in an implicit production task with event-related brain potentials (ERPs) recorded from 61 scalp positions in 18 participants. The topography of a slow negative wave, which accompanied the implicit production of the multiplication result, varied with problem type. In comparison to small problems, larger problems evoked a stronger negativity over fronto-central and right temporal sites, and zero problems evoked a left anterior negativity. These topographic differences indicate not only that zero and small nonzero problems are solved by means of distinct strategies-most likely rule application vs. fact retrieval-but also that larger, less practiced problems invoke other processes than pure fact retrieval. Moreover, ERPs showed a positive deflection around 450 ms with a centro-parietal topography (P300), whose amplitude reflected differences in anticipated problem difficulty.