非表示:
キーワード:
Multilingualism
要旨:
Reaching a native-like level in a second language includes mastering phoneme contrasts that are not distinguished in one’s mother tongue – both in perception and production. This study explores how those two domains interact in the course of learning and how behavioural changes in both listening and speaking ability are related to traceable changes in the brain. Unravelling the processes underlying speech category learning could guide the design of more efficient training methods. Production and perception processes could support each other during learning, or they could interfere with each other. Baese-Berk et al. (2010), for instance, observed delayed learning when perceptual training was combined with production practice compared to perception-only training. These results could indicate perception-production interference but could also be explained by differences in cognitive load between the two conditions. In order to disentangle the added value of production training in perceptual category learning, we systematically contrasted the combination of perceptual training with either related or unrelated production. Thirty-one native speakers of Dutch distributed between two groups participated in a 4-day high-variability training protocol on the British-English /æ/-/ε/ vowel contrast (multiple words spoken by multiple talkers). In the related production group (n=15) feedback on a perceptual categorisation task was combined with pronouncing the respective correct word on every trial, whereas it was combined with pronouncing a matched but phonologically unrelated set of words in the unrelated production group (n=16). Cognitive load was matched between groups. Pre- and post-training measurements were taken of both perceptual abilities (in an identification task, an identification task assessing category boundaries on a morphed continuum, and a discrimination task on the same continuum) and production ability (a reading-aloud task with a list of isolated words). All auditory stimulus words during the training were presented according to a classical oddball paradigm, while the electrophysiological activity was recorded continuously. This enabled us to track neural changes in auditory discrimination ability using the mismatch negativity response (MMN). Results indicate that participants’ perceptual ability significantly improved over the course of training. No significant difference in perceptual learning arose between the two groups. Measurements of the distribution of formants F1 and F2 in the words in the production task before and after training (quantified in terms of Mahalanobis distance) showed that participants in both groups significantly improved after training: the two English target vowels became acoustically more distinct. Analyses of the electrophysiological data and of the other behavioural tasks are ongoing and will be presented. The fact that participants’ perceptual ability improved similarly regardless of whether they also practiced the respective productions could be seen as evidence that the perception and production systems for non-native vowels are separate. A more likely explanation, however, is that the added value of practicing the pronunciation of the vowels might have been counteracted – especially early in training - by exposure to sub-optimal utterances as the participants listened to their own voices. In order for production practice to be beneficial for the learner, immediate and informative feedback on production outcomes might be necessary.
