D. E. Ronan
R. M. Uchanski
L. D. Braida
Res. Lab. of Electron., MIT, Cambridge, MA 02139
Uchanski et al. [J. Acoust. Soc. Am. 90, 2254 (A) (1991)] reported significant sensitivity differences between discrimination experiments in which each vowel was represented by only four tokens (utterances) and experiments in which the same four tokens were embedded in a larger set of 16 tokens. In present experiments, the set size was fixed at 8 but the specific tokens representing one vowel were changed while those representing the other vowel were fixed. Listeners attempted to discriminate between the vowels /ae/ and /ah/ occurring in distorted [M. R. Schroeder, J. Acoust. Soc. Am. 44, 1735--1736 (1968)] /h/--V--/d/ syllables. Sensitivity was found to be more highly correlated ((rho)(approximately equal to)0.8) across conditions for a given subject than across subjects for a given condition ((rho)(approximately equal to)0.5). This suggests that each subject weighted the available discrimination cues in a fairly stable fashion across conditions, but that the weights varied from subject to subject. Multiple regression analyses indicate that sensitivity can be accounted for by a small set of physical parameters of the undistorted syllables: F2, F0, and syllable duration.