The non-native phonetic perception mechanism utilized by bilinguals with different L2 proficiency levels

Aims: The present study investigated whether bilinguals differing in L2 proficiency are different in their non-native phonetic perception mechanism. Methodology: An event-related potential (ERP) experiment was conducted, in which high and low L2 proficiency bilinguals were asked to focus their attention on a muted film while listening pre-attentively to phoneme contrasts arranged in the Oddball paradigm. Non-native and native phonetic conditions were investigated in two separate blocks. Data and analysis: The mean amplitudes of the ERP epochs time-locked to the onset of phonemes were analyzed within four consecutive time windows: 50-150 ms, 150-250 ms, 250-350 ms, and 350-600 ms. Repeated measures analyses were performed on the following factors: phonetic condition (non-native vs. native) x deviancy (standard vs. deviant) x brain region (frontal vs. parietal) x proficiency (high vs. low). Phonetic condition, deviancy, and brain region were within-subjects factors, whereas proficiency was a between-subjects factor. Findings: In the non-native phonetic condition, a deviancy effect in the form of mismatch negativity (MMN) and late discriminative negativity (LDN) ERP components was observed in bilinguals with high L2 proficiency, whereas the P3b and late positive component (LPC) were found in those with low L2 proficiency. In the native phonetic condition, the two proficiency groups were the same in the deviancy effect as manifested by their similar brain responses in the form of the MMN component. Originality: This was the first study to take native phonetic condition into consideration while investigating the relationship between L2 proficiency and non-native phonetic discrimination. Significance/implications: The current findings suggest that high L2 proficiency might be related to faster involuntary phonetic discrimination and efficient high-level phonetic evaluation, whereas low L2 proficiency bilinguals may need to rely on additional memory processing. Findings of this study provide more evidence for the perceptual plasticity in pre-attentive non-native phonetic processing as a function of L2 proficiency.