Listening effort during speech perception enhances auditory and lexical processing for non-native listeners and accents

Speech communication in a non-native language (L2) can feel effortful, and the present study suggests that this effort affects both auditory and lexical processing. EEG recordings (electroencephalography) were made from native English (L1) and Korean listeners while they listened to English sentences spoken with two accents (English and Korean) in the presence of a distracting talker. Neural entrainment (i.e., phase locking between the EEG recording and the speech amplitude envelope) was measured for target and distractor talkers. L2 listeners had relatively greater entrainment for target talkers than did L1 listeners, likely because their difficulty with L2 speech recognition caused them to focus more attention on the speech signal. N400 was measured for the final word in each sentence, and L2 listeners had greater lexical processing in high-predictability sentences than did L1 listeners. L1 listeners had greater target-talker entrainment when listening to the more difficult L2 accent than their own L1 accent, and similarly had larger N400 responses for the L2 accent. It thus appears that the increased effort of L2 listeners, as well as L1 listeners understanding L2 speech, modulates their auditory and lexical processing during speech recognition. This may provide a mechanism to compensate for their perceptual challenges under adverse conditions.