Slide Slam R2
Sensorimotor Adaptation in Bilingual Speech
Douglas Shiller1, Sarah Bobbitt2, Daniel Lametti2; 1Université de Montréal, Montreal, Canada, 2Western University, London, Ontario, Canada, 3Acadia University, Wolfville, Nova Scotia, Canada
Sensorimotor adaptation in speech is typically studied by altering the sound of the voice as vowel sounds are produced. After a period of baseline production, the formant structure of the vowel sound is altered in real-time so that participants hear a different vowel from the one they intended to produce. Over hundreds of trials, adaptation is observed; participants alter their formant productions to offset the induced acoustical error. We recently demonstrated that sensorimotor adaptation like this can also be observed during the production of complex sentences (Lametti et al. 2018). Here we expand on this idea to examine the relationship between language and sensorimotor control in speech. In a group of L1 French / L2 English bilinguals, we use the rich linguistic environment afforded by sentence production to test whether sensorimotor adaptation acquired during French sentence production could be applied to vowel production in English, and vice versa. Participants read matched French and English sentences into a microphone as they appeared on a computer screen and heard themselves in real-time through headphones. After a period of baseline production, the first and second formant frequency of all produced vowels was altered by -49.5 mel and +49.5 mel (respectively) to induce sensorimotor adaptation. Before and after adaptation, a transfer test involving the production of isolated words with noise masking assessed formant production in the complete absence of auditory feedback. The transfer test consisted of randomized productions of eight English words and eight French words with comparable vowel sounds (e.g., “pat” and « patte »). Twenty adult participants were tested (10 male, 10 female), all of whom were L1 speakers of Quebec French and moderate/high proficiency speakers of English. Subjects were tested in two sessions, one week apart. In one session, they experienced sensorimotor adaptation during English sentence production, and the extent of transfer to both English and French words was assessed; in the second session, they experienced sensorimotor adaptation during French sentence production, and the extent of transfer to English and French words was assessed. Session language order was balanced across the 20 participants. Speech adaptation was indexed by the degree to which changes in formant production opposed the formant alteration. Participants offset 30-35% of the induced acoustical error in both languages. Compensatory speech patterns learned in the context of French sentence production were readily applied to the production of both French and English words. Compensation acquired during English sentence production similarly showed robust transfer to word production in both English and French. These results suggest that, in speakers of more than one language, newly acquired sensorimotor transformations in speech may not be language specific, but rather are applied to vowels across language contexts.