Pursuit auditory tracking of dichotically presented tonal amplitudes.

In pursuit auditory tracking tasks subjects match a continuously varying pure tone presented to one ear with a second tone presented to the other ear and controlled by unidimensional movements of part of their motor system. In previous studies in which tonal frequency was varied, performance was significantly better when the tone controlled by a speech articulator (tongue, jaw) was presented to the right ear, rather than the left, but not if the tone was hand controlled. In this study tonal amplitude was varied in mandibular and manual tracking by 30 normal right-handed subjects. Small right-ear advantage was found for both tracking modes although it did not reach statistical significance. Frequency modulated stimuli may more effectively differentiate speech from nonspeech tracking because we may, as a result of speech experience, possess a more developed lateralized auditory-sensorimotor algorithm for frequency-motor relationships involving the mandible than for amplitude-motor relationships. Testable consequences of this hypothesis are outlined.