The purpose of the research presented here was to systematically investigate the role of speech perception on speech production in speakers of different ages and those with PD and hypokinetic dysarthria. For this, the experimental designs of auditory perturbation and mimicry were chosen. The initial research phase established that the magnitude of compensation to auditory vowel perturbation was reduced in 54 speakers of New Zealand English (NZE) when compared to previous studies conducted with speakers of American (AE) and Canadian English (CE). A number of factors were studied to determine possible predictors of compensation and distinguish between potential changes associated with ageing. However, no predictors of compensation were found for the overall group. Post-hoc analyses established an increased variability in response patterns in NZE when compared to previous studies of AE and CE. Subsequent follow-up analyses focused on the response-dependent categories of (1) big compensators, (2) compensators, (3) big followers, and (4) followers. Linear mixed-effect modelling revealed that in big compensators, the magnitude of compensation was greater in speakers who exhibited larger F1 baseline standard deviation and greater F1 vowel distances of HEAD relative to HEED and HAD. F1 baseline standard deviation was found to have a similar predictive value for the group of compensators. No predictors of compensation were found for the other two subgroups. Phase two was set up as a continuation of phase one and examined whether a subset of 16 speakers classified as big compensators adapted to auditory vowel perturbation. Linear mixed-effect modelling revealed that in the absence of auditory feedback alterations, big compensators maintained their revised speech motor commands for a short period of time until a process of de-adaptation was initiated. No predictors of adaptation were found for the group. Due to the unexpected results from the first two research phases indicating a dominant weighting of somatosensory feedback in NZE compared to auditory-perceptual influences, a different experimental paradigm was selected for phase three - mimicry. The purpose of this study was to determine whether eight speakers with PD and dysarthria and eight age-matched healthy controls (HC) are able to effectively integrate speech perception and speech production when attempting to match an acoustic target. Results revealed that all speakers were able to modify their speech production to approximate the model speaker but the acoustic dimensions of their speech did not move significantly closer to the target over the three mimicry attempts. Although speakers with moderate levels of dysarthria exhibited greater acoustic distances (except for the dimension of pitch variation), neither the perceptual nor the acoustic analyses found significant differences in mimicry behaviour across the two groups. Overall, these findings were considered preliminary evidence that speech perception and speech production can at least to some extent be effectively integrated to induce error-correction mechanisms and subsequent speech motor learning in these speakers with PD and dysarthria.

abstract: Studies in Second Language Acquisition and Neurolinguistics have argued that adult learners when dealing with certain phonological features of L2, such as segmental and suprasegmental ones, face problems of articulatory placement (Esling, 2006; Abercrombie, 1967) and somatosensory stimulation (Guenther, Ghosh, & Tourville, 2006; Waldron, 2010). These studies have argued that adult phonological acquisition is a complex matter that needs to be informed by a specialized sensorimotor theory of speech acquisition. They further suggested that traditional pronunciation pedagogy needs to be enhanced by an approach to learning offering learners fundamental and practical sensorimotor tools to advance the quality of L2 speech acquisition. This foundational study designs a sensorimotor approach to pronunciation pedagogy and tests its effect on the L2 speech of five adult (late) learners of American English. Throughout an eight week classroom experiment, participants from different first language backgrounds received instruction on Articulatory Settings (Honickman, 1964) and the sensorimotor mechanism of speech acquisition (Waldron 2010; Guenther et al., 2006). In addition, they attended five adapted lessons of the Feldenkrais technique (Feldenkrais, 1972) designed to develop sensorimotor awareness of the vocal apparatus and improve the quality of L2 speech movement. I hypothesize that such sensorimotor learning triggers overall positive changes in the way L2 learners deal with speech articulators for L2 and that over time they develop better pronunciation. After approximately eight hours of intervention, analysis of results shows participants’ improvement in speech rate, degree of accentedness, and speaking confidence, but mixed changes in word intelligibility and vowel space area. Albeit not statistically significant (p >.05), these results suggest that such a sensorimotor approach to L2 phonological acquisition warrants further consideration and investigation for use in the L2 classroom. / Dissertation/Thesis / Doctoral Dissertation English 2015