Rahul Chakraborty

Mapping of prosodic structure onto words and phrases in children's and adults' speech production

Direct recordings of lip and jaw movement were obtained to investigate how children and adults differentiate prosodic structure both within iambic and trochaic words and across word boundaries. It was hypothesised that children, especially those with less language skills, would be particularly likely to produce strong-weak (or trochaic) sequences. This experiment examined childrens (both normally developing and specifically language impaired, aged 4–6 years) and adults’ productions of prosodic sequences that were controlled for syntactic and phonetic content, but that differed in rhythmic alternations, both within words (i. e., iambs vs. trochees) and across words (i. e., optimal strong-weak vs. stress gap or stress clash). To avoid final position effects, target words were in utterance internal position. Analyses included kinematic measures of prosodic structure (i. e., amplitude and duration of movements in weak vs. strong syllables; ratios of weak-to-strong movements). Consistent with prior work, weak syllables in iambs were produced differentially from those in trochees; though these effects were now observed in utterance position. However, in noun-noun sequences within a phrase, even when the rhythm rule was violated, prosodic foot structure was not reorganised as a function of rhythmic properties of the utterance. Overall, children with the least mature language skills demonstrated poor control of temporal and amplitude aspects of movement, especially in weak syllables. Findings are related to the organisation of speech production units across prosodic levels.

Influence of L2 Proficiency on Speech Movement Variability: Production of Prosodic Contrasts by Bengali-English Speakers.

This paper examines the influence of age of immersion and proficiency in a second language on speech movement consistency in both a first and a second language. Ten monolingual speakers of English and 20 Bengali–English bilinguals (10 with low L2 proficiency and 10 with high L2 proficiency) participated. Lip movement variability was assessed based on bilingual participants’ production of four real and four novel words embedded in Bengali (L1) and English (L2) sentences. Lip movement variability was evaluated across L1 and L2 contexts for the production of real and novel words with trochaic and iambic stress pattern. Adult bilinguals produced equally consistent speech movement patterns in their production of L1 and L2 targets. Overall, speakers’ L2 proficiency did not influence their movement variability. Unlike children, the speech motor systems of adult L2 speakers exhibit a lack of flexibility which could contribute to their increased difficulties in acquiring native-like pronunciation in L2.

Invariant principles of speech motor control that are not language-specific

Abstract Bilingual speakers must learn to modify their speech motor control mechanism based on the linguistic parameters and rules specified by the target language. This study examines if there are aspects of speech motor control which remain invariant regardless of the first (L1) and second (L2) language targets. Based on the age of academic exposure and proficiency in L2, 21 Bengali–English bilingual participants were classified into high (n = 11) and low (n = 10) L2 (English) proficiency groups. Using the Optotrak 3020 motion sensitive camera system, the lips and jaw movements were recorded while participants produced Bengali (L1) and English (L2) sentences. Based on kinematic analyses of the lip and jaw movements, two different variability measures (i.e., lip aperture and lower lip/jaw complex) were computed for English and Bengali sentences. Analyses demonstrated that the two groups of bilingual speakers produced lip aperture complexes (a higher order synergy) that were more consistent in co-ordination than were the lower lip/jaw complexes (a lower order synergy). Similar findings were reported earlier in monolingual English speakers by Smith and Zelaznik. Thus, this hierarchical organization may be viewed as a fundamental principle of speech motor control, since it is maintained even in bilingual speakers.

Influence of Early and Late Academic Exposure to L2 on Perception of L1 and L2 Accent

This paper explored the influence of early and late academic exposure to an L2 (English) on the perception of L1 (Bengali) and L2 (English) accent. Based on the perception of real and novel words in L1 and L2 contexts, 12 monolingual Bengali listeners and 12 monolingual Standard American English listeners judged the “nativelike” accent of 20 Bengali-English bilingual speakers (10 speakers had early and 10 had late academic exposure to an L2). In each stimulus category (i.e., real and novel), 2 words had trochaic and 2 words had iambic stress pattern. Except in the L1 novel context, speakers with early L2 exposure received higher “nativelike” accent ratings in both L1 and in L2. The two groups of bilinguals were comparable in the L1 novel context. Real words with trochaic stress pattern were perceived as more “nativelike” in both L1 and L2 contexts. The results suggest that the age of academic exposure to an L2 differentially interacts with the perception of L1 and L2 accent, and with perception based on the novelty of the stimuli. Cross-linguistic transfer alone might not always explain bilinguals’ linguistic behaviors. Active interplay of multiple social, linguistic, and physiological factors needs to be considered.