Integrality of nasalization and F-1. II. Basic sensitivity and phonetic labeling measure distinct sensory and decision-rule interactions

In vowel perception, nasalization and height (the inverse of-the first form ant, F-1) interact. This paper-asks whether the interaction results from a sensory process, decision mechanism, or both. Two experiments used vowels v arying in height, degree of nasalization, and three other stimulus paramete rs: the frequency region of F-1, the location of the nasal pole/zero comple x relative to F-1, and whether a consonant following the vowel was oral or nasal. A fixed-classification experiment, designed to estimate basic sensit ivity between stimuli, measured accuracy for discriminating stimuli differi ng in F-1, in nasalization, and on both dimensions. A configuration derived by a multidimensional scaling analysis revealed a perceptual interaction t hat was stronger for stimuli in which the nasal pole/zero complex was below rather than above the oral pole, and that was present before both nasal an d oral consonants. Phonetic identification experiments, designed to measure trading relations between the two dimensions, required Listeners to identi fy height and nasalization in vowels varying in both. Judgments of nasaliza tion depended on F-1 as well as on nasalization, whereas judgments of heigh t depended primarily on F-1, and on nasalization more when the nasal comple x was below than above the oral pole. This pattern was interpreted as a dec ision-rule interaction that is distinct from the interaction in basic sensi tivity. Final consonant nasality had little effect in the classification ex periment; in the identification experiment, nasal judgments were more likel y when the following consonant was nasal. (C) 1999 Acoustical Society of Am erica. [S0001-4966(99)00511-1].