Event-related brain potentials in lexical processing with Chinese characters show effects of contextual diversity but not word frequency.

Abstract

The diversity of contexts in which a word occurs, operationalized as CD, is strongly correlated with response times in visual word recognition, with higher CD words being recognized faster. CD and token word frequency (WF) are highly correlated but in behavioral studies when other variables that affect word visual recognition are controlled for, the WF effect is eliminated when contextual diversity (CD) is controlled. In contrast, the only event-related potential (ERP) study to examine CD and WF Vergara-Martínez et al., Cognitive, Affective, & Behavioral Neuroscience, 17, 461-474, (2017) found effects of both WF and CD with different distributions in the 225- to 325-ms time window. We conducted an ERP study with Chinese characters to explore the neurocognitive dynamics of WF and CD. We compared three groups of characters: (1) characters high in frequency and low in CD; (2) characters low in frequency and low in CD; and (3) characters high in frequency and high in CD. Behavioral data showed significant effects of CD but not WF. Character CD, but not character frequency, modulated the late positive component (LPC): high-CD characters elicited a larger LPC, widely distributed, with largest amplitude at the posterior sites compared to low-CD characters in the 400-to 600-ms time window, consistent with earlier ERP studies of WF in Chinese, and with the hypothesis that CD affects semantic and context-based processes. No WF effect on any ERP components was observed when CD was controlled. The results are consistent with behavioral results showing CD but not WF effects, and in particular with a "context constructionist" framework.