This study investigated cognitive processing during silent and oral reading. We focused on the allocation of cognitive resources required for reading comprehension and phonological representation. We examined the utilization of cognitive resources by observing the effect of concurrent tapping on the comprehension of visually presented sentences. We also analyzed the impact of the presentation of irrelevant speech on reading comprehension. Thirty-two participants read sentences both silently and orally. Each reading task was performed under four multiple-task conditions: no-tap⁄no-speech, no-tap⁄speech, tap⁄no-speech, and tap⁄speech. The results indicated that for silent reading, tapping interfered with reading comprehension. Irrelevant speech also interfered with reading comprehension when the readers did not perform the tapping. However, when the readers performed the tapping during the silent reading task, there was no additional disruptive effect of the irrelevant speech. In contrast, for oral reading, neither tapping nor irrelevant speech interfered with reading comprehension. Moreover, there was no interaction between the effects of tapping and irrelevant speech when the participants read the sentences orally. These findings suggest that more cognitive resources are used for silent reading comprehension than for oral reading comprehension. Also, more cognitive resources during silent reading are required to use the phonological representations constructed internally and to support reading comprehension.
