An ERP study on the processing of common fractions.

The aim of this study was to examine how adults processed common fractions with common numerators under two distinct conditions. Whereas participants were presented with only common fractions in a "simple" condition, a "complex" condition involved the random presentation of common fractions as well as decimal fractions. In both conditions, participants were required to assess whether various "target" fractions were larger than or smaller than a "standard" common fraction (1/5). Behavioral results indicated that under both conditions, participants mentally processed the fractions componentially in terms of their constituent parts rather than holistically in terms of the numerical value of the fraction as a whole. The data provided by the event-related potentials (ERPs) demonstrated electrophysiological correlates of the componential processing of common fractions in the simple condition, as reflected in the latency and amplitude of P3. However, in contrast to what the behavioral data showed, there was no strong electrophysiological evidence to indicate that common fractions were accessed componentially in the complex condition. In addition, the complex condition was linked to longer latency and more negative amplitude of N2 over the frontal scalp than the simple condition, which could be attributed to the fact that the comparison of fractions in the complex condition involved task switching and thus was more taxing on cognitive control than the simple condition.