Brain Potentials to Speech and Acoustic Sound Discrimination Uncover the Origin of Individual Differences in Perceiving the Sounds of A Second Language

Abstract

As to the origin of individual differences in perceiving the sounds of a second language, the scientific community has been divided. There are two alternative explanations; a general psychoacoustic origin vs. a general speech one. A previous study (Diaz et al., 2008) has shown that such individual variability is linked to the perceivers' general speech abilities. However, our research casts doubt on the conclusion for two reasons. Firstly, this study exclusively focused on speech sounds in the same language family, rather than explored the languages from different language families. It has only been proved that individual variability in L2 is related to varied sensitivities to the speech sounds within the same language family rather than in the general speech system including different language families. Moreover, the study selected pure tones as acoustic materials, neglecting another important acoustic signals, complex sounds. It is obvious that we can't draw the conclusion that ability of processing general sounds has no impact on discrimination of speech sounds in L2, without studying complex tones. Here, studying speech sounds from different language families and complex sounds, the main purpose of present study was to explore whether the individual differences in perceiving L2 stem from their ability of processing general phonetic signals or phonetic stimuli within the specific language family, and farther explore whether such individual variability deeply stems from individual sensitivity to complex tones. In the present study, 14 L2 good perceivers (GP) and 14 L2 poor perceivers (PP), in order to participate in the following ERP experiment, were selected from 130 healthy Cantonese (Ll)-mandarin (L2) bilinguals according to their performances in a behavior task. To precisely measure the participants' sound discrimination, MMN elicited by oddball paradigm was recorded in the following experiment. The ERP experiment consists of three sections, including native speech sounds, speech sounds in different language families and complex tones. And every participant took part in all three material sections. The results showed that significant differences between GP and PP were found when the two groups were presented with all 3 stimuli: GP showed larger MMN responses to both phonetic and acoustic stimuli than PP. This result reveals individual differences in discriminating the sounds in L2 not only stem from their sensitivity to phonetic sounds but also ultimately from their sensitivity to acoustic signals. (PsycINFO Database Record (c) 2016 APA, all rights reserved)