Poster A108, Saturday, March 25, 5:00 – 7:00 pm, Pacific Concourse
Sensorimotor adaptation to real-time formant shifts is influenced by the direction and magnitude of shift.
Hardik Kothare1, Vikram Ramanarayanan2, Benjamin Parrell3, Srikantan Nagarajan1, John Houde1; 1University of California, San Francisco, 2Educational Testing Service R&D, 3University of Delaware
Alteration in auditory feedback engenders a change in speech production. The speech motor control system learns to anticipate and compensate for consistent feedback alterations. This sensorimotor adaptation persists temporarily even after feedback returns to normal. Does the nature of sensorimotor adaptation depend on the size and direction of the feedback alteration? To investigate this, we employed real-time auditory feedback alteration to shift the frequency values of the first and second formants (F1 and F2) of participants’ speech. The experiment comprised six cases; the shift was towards a different vowel in each case. In each case, participants produced 90 repetitions of the nonsense word ‘bep’. A case started with a non-altered block of 10 trials, followed by a block of 50 trials with a constant alteration and then by a non-altered washout block of 30 trials. We find that adaptation depends on the magnitude and direction of the auditory error rather than giving equal weight to any possible error. In general, smaller shifts lead to a relatively larger adaptation. A vector resolution analysis of the response vectors reveals that both the component orthogonal to the shift axis and the component parallel to the shift axis influence the magnitude of adaptation. All shifts, except the one from /ɛ/ to /u/, elicit a response of a compensatory nature. These results suggest that the adaptive feedback response in speech is complex and specifically more sensitive to errors in a local neighbourhood around speech motor targets.
Topic Area: PERCEPTION & ACTION: Motor control