An Electrophysiological Dual-Task Study of Visual Word Processing without Task Switching

Abstract

A previous dual-task study (Lien, Ruthruff, Cornett, Goodin, & Allen, 2008) provided evidence that people have difficulty identifying words while central attention is devoted to another non-word task. In that study, participants performed an auditory Task 1 regarding tone pitch and a visual word Task 2. However, it’s possible that the real obstacle to word identification was not the lack of central attention, but rather the required task switch. The present study therefore examined this issue by using a dual-task paradigm in which participants performed essentially the same word task for both Task 1 and Task 2 (i.e., there was no task switch). We measured the N400 effect elicited by Task-2 word, a measure of whether participants detected a mismatch between the word and the current semantic context. The N400 effect can occur only if a word has been identified. We found that the N400 effect was strongly attenuated for Task-2 words presented nearly simultaneously with Task-1 words. This finding suggests that, even without task switching, words still cannot be identified without central attentional resources.