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Purpose Somatosensory targets and feedback are instrumental in ensuring accurate speech production. Individuals differ in their ability to access and respond to somatosensory information, but there is no established standard for measuring somatosensory acuity. The primary objective of this study was to determine which of three measures of somatosensory acuity had the strongest association with change in production accuracy in a vowel learning task, while controlling for the better studied covariate of auditory acuity. Method Three somatosensory tasks were administered to 20 female college students: an oral stereognosis task, a bite block task with auditory masking, and a novel phonetic awareness task. Individual scores from the tasks were compared to their performance on a speech learning task in which participants were trained to produce novel Mandarin vowels with visual biofeedback. Results Of the three tasks, only bite block adaptation with auditory masking was significantly associated with performance in the speech learning task. Participants with weaker somatosensory acuity tended to demonstrate larger increases in production accuracy over the course of training. Conclusions The bite block adaptation task measures proprioceptive awareness rather than tactile acuity and assesses somatosensory knowledge implicitly, with limited metalinguistic demands. This small-scale study provides preliminary evidence that these characteristics may be desirable for the assessment of oral somatosensory acuity, at least in the context of vowel learning tasks. Well-normed somatosensory measures could be of clinical utility by informing diagnosis/prognosis and treatment planning. Supplemental Material https://doi.org/10.23641/asha.14044082

Speech production is directed by auditory and somatosensory targets that shape and update the motor plan through corresponding feedback channels (Guenther, 2016). Somatosensory feedback is instrumental in ensuring accurate articulator placement, as shown in studies where perturbed somatosensory feedback leads to reduced speech precision (Ringel and Steer, 1963; Gammon et al., 1971; Jones and Munhall, 2003). As no gold standard for measuring somatosensory acuity exists, the current study will compare three measures in 20 adults: (1) an oral stereognosis task (Steele et al., 2014) measuring tactile input received by the articulators; (2) a novel phonetic awareness task measuring the proprioceptive sense of articulator position; (3) a bite-block task with auditory masking (Zandipour et al., 2006) measuring the degree of compensation for perturbation using only somatosensory feedback. To test the hypothesis that participants with higher somatosensory acuity showed larger increases in production accuracy, participants’ scores on each task will be used to predict performance in an L2 vowel learning task (Li et al., in press). Three linear regression models will be fit, one for each somatosensory measure. The model that best explains change in production accuracy will be selected using the Akaike/Bayes Information Criteria. Establishing a valid measure of somatosensory acuity will enable future research to elucidate somatosensory influences on speech production.

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