Resolution for speech sounds: Basic sensitivity and context memory on vowel and consonant continua

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Abstract
Discrimination and identification experiments were performed for a vowel continuum (/i/-/i/-/.epsilon./) and two consonant continua (/ba/-/pa/ and /ba/-/da/-/ga/). The results were interpreted in terms of a generalization of a theory of intensity resolution [N.I. Durlach and L.D. Braida, J. Acoust. Soc. Am. 46, 372-383 (1969)] that makes precise the distinction between basic sensitivity (sensory-based resolution) and context coding (labeling processes). On the vowel continuum, basic sensitivity increased gradually across the range whereas, for both consonant continua, sensitivity peaked between phonetic categories. All speech continua were found to have small ranges (measured in jnd''s); context memory was good, and better for consonants than for vowels. The stimuli that could be labeled most reliably were near the category boundaries on the vowel continuum, but near good phonetic exemplars for consonants. Introduction of a standard in identification primarily altered response bias, not sensitivity.