Comparing the Perceptual Abilities of Monolinguals, Bilinguals and Multilinguals: A Combined Behavioural and Event-Related Potential Experiment

Abstract

The aim of the experiment was to determine whether multilingualism contributes to the development of greater perceptual sensitivity to non-native speech contrasts. Combining an AX discrimination task and an Event-Related Potential experiment using an oddball paradigm, monolinguals, bilinguals and multilinguals were compared in their ability to discriminate a non-native contrast before and after receiving training as well as in their ability to transfer this training to a new but similar contrast. The experiment was based on a "pre-test -- training -- post-test" design, with 4 to 5 days between sessions. At the behavioural level, the effect of Group was significant only at Post-Test for the experimental contrast. Post-hoc analyses indicated that multilinguals were significantly more accurate than all of the other groups except for late bilinguals who were also more accurate than the control group which did not receive training. Moreover, multilinguals and late bilinguals were the only groups which improved significantly from Pre-Test to Post-Test. At the neurophysiological level, the effect of Group reached significance at Pre-Test for the experimental contrast and at Post-Test for both the experimental and transfer contrasts. At Pre-Test and Post-Test, monolinguals, late bilinguals and the control group exhibited a Mismatch Negativity (MMN) in the midline and the right side electrodes, while multilinguals and early bilinguals exhibited a bilateral MMN. The increase in MMN amplitude from Pre-Test to Post-Test was greater for multilinguals and both groups of bilinguals, compared to monolinguals and the control group. As for the Test of Transfer, monolinguals and the control group exhibited a right lateralised MMN, while multilinguals and both groups of bilinguals exhibited a bilateral MMN. The results of the behavioural and ERP experiments indicate that multilinguals and bilinguals have enhanced perceptual sensitivity and a greater ability to learn a new contrast. Multilingualism seems to boost perceptual sensitivity and learning abilities. Moreover, the age at which a second language is learned may affect speech perception at both levels differently. Finally, since initial group differences were only found in the ERP data, the results indicate that differences at the neurophysiological level may transpire before or without any differences at the behavioural level.