アラル須本 宝・ケンザ

Second language learners and educators often believe that improving one's listening ability hinges on acquiring an extensive vocabulary and engaging in thorough listening practice. Our previous study suggested that listening comprehension is also impacted by the ability to produce vocabulary. Nevertheless, it remained uncertain whether quick comprehension could be attributed to a simple acceleration of processing or to changes in neural activity. To identify neural activity changes during sentence listening comprehension according to different levels of lexical knowledge (productive, only comprehensive, uncomprehensive), we measured participants' electrical activity in the brain via electroencephalography (EEG) and conducted a time-frequency-based EEG power analysis. Additionally, we employed a decoding model to verify the predictability of vocabulary knowledge levels based on neural activity. The decoding results showed that EEG activity could discriminate between listening to sentences containing phrases that include productive knowledge and ones without. The positive impact of productive vocabulary knowledge on sentence comprehension, driven by distinctive neural processing during sentence comprehension, was unequivocally evident. Our study emphasizes the importance of productive vocabulary knowledge acquisition to enhance the process of second language listening comprehension.

Second language learners tend to focus more on learning the meaning of vocabulary than on how to use it in their speech and writing. Although comprehensive vocabulary knowledge is necessary for understanding sentences, productive vocabulary knowledge may also have a positive impact on sentence comprehension. Most studies examining the relationship between production and comprehension have compared these abilities between participants or evaluated unrelated criteria between tasks, which may be insufficient for examining the direct effects of productive knowledge on sentence comprehension. Our study investigates changes in sentence comprehension speed during listening, and we used a within-subjects comparison to examine the effect of productive vocabulary knowledge or the lack thereof. We applied generalized linear mixed models to investigate productive vocabulary knowledge effects by partialing out other influential factors, such as confidence, frequency of target words, stimulus duration, and individual differences. The results showed that the sentences with a producible phrase were processed faster than the sentences that included phrases with only comprehensive knowledge or no comprehension. The effect of productive vocabulary knowledge on the speed of sentence comprehension was directly examined with a within-subject comparison, and its contribution was clearly found. This study emphasizes the value of productive vocabulary knowledge acquisition in enhancing the speed of sentence comprehension.