Aimee M. Surprenant
Diane Kewley-Port
Dept. of Speech and Hear. Sci., Indiana Univ., Bloomington, IN 47405
The ability to ignore irrelevant variation in the speech signal is essential for normalizing across speakers and situations. Past research has indicated that irrelevant variation in such features as pitch and vowel quality caused more interference on a consonant classification task than the reverse. Along with other more memory-oriented paradigms such as serial-list recall, this has been taken as evidence that the longer-lasting, periodic elements of sound that make up vowel and pitch information remain longer in auditory memory, thereby interfering with judgments about consonant identity. However, in most of these demonstrations, the relative discriminability of the tokens was not controlled. In the present study, discriminability was assessed for continua of pitch, consonant and vowel identity for stop-vowel syllables. Eight well-trained subjects were asked to make speeded same--different judgments on one dimension of stimuli that varied on two dimensions. An interaction for both response time and accuracy was found such that as the discriminability of the relevant dimension was increased, interference from the irrelevant dimension decreased and vice versa. Although there were minor variations, the same general pattern was observed in all conditions. [Research supported by NIDCD.]