ASA 124th Meeting New Orleans 1992 October

1aSP11. Assimilative and contrast effects of speaking rate on speech perception.

Rochelle S. Newman

James R. Sawusch

Dept. of Psychol., SUNY at Buffalo, Buffalo, NY 14260

Previously, results were presented showing that varying the duration of a distal vowel can produce assimilatory, rather than contrastive effects on perception. In a /shwas/--/chwas/ series, a longer vowel yielded more /sh/ responses rather than more /ch/ responses. Varying /w/ duration produced the standard contrast effect. The assimilative effect may reflect a chaining of contrast effects: the long /a/ made the /w/ seem shorter, and the ``shorter'' /w/ made the initial segment seem longer. Alternatively, the lack of a distinct acoustic boundary between /w/ and /a/ may have produced these results, in which case results should be very different for a voiceless stop followed by a vowel. In new experiments, a similar series was made ranging from /chkas/ to /shkas/, and the /k/ and /a/ durations were varied separately. The /k/ produced the usual contrast effect while the nonadjacent /a/ had no effect. These results and their implications for the understanding of rate normalization will be discussed. [Work supported by NIDCD Grant No. DC00219 to SUNY at Buffalo and an NSF Graduate Fellowship to the first author.]