Coping with noise at multiple levels: Auditory cortical and lexical effects of maskers for native and non-native listeners
Non-native listeners (L2) have more difficulty than native speakers (L1) in noise, but L2 listeners appear to track the acoustics of a target speaker better than do L1 listeners, as measured by cortical entrainment to the speech envelope. In contrast, L1 speakers appear to have more flexibility in lexical processing (i.e., N400) depending on the listening situation. The present study investigated these issues within listening conditions that vary the demands on peripheral and central processing: babble vs. single-talker maskers and a masker collocated with the target or 45° away. Native English and Korean subjects listened to English sentences, and pressed a button when they heard catch trials that did not make sense. EEG recordings were used to measure cortical entrainment to the speech envelope and N400.
The results confirmed previous work that non-native listeners have greater cortical entrainment for target speakers than do native listeners. However, their target-speech entrainment was differentially modulated by masker type, with greater entrainment in the no-masker condition, whereas entrainment by native listeners was less affected by the masker. The N400 effect for target sentences was smaller for non-native than native listeners overall. However, native listeners varied lexical processing depending on the masker, having larger N400 responses when there was a single-talker masker. The results thus suggest that noise can produce different effects for L1 and L2 listeners, and that L1 listeners may be better able to use more processes to cope with informational masking (e.g., searching more thoroughly for a lexical competitor).