Second International Conference on Spoken Language Processing (ICSLP'92)

Banff, Alberta, Canada
October 13-16, 1992

Effects of Typicality and Interstimulus Interval on the Discrimination of Speech Stimuli: Within-Subject Comparison

Minoru Tsuzaki

ATR Auditory and Visual Perception Research Laboratories, Kyoto, Japan

To investigate how learned knowledge would affect the perceptual judgment for speech sounds as well as how such effects would chagne during the processing time and retention interval, Japanese listeners were tested with the AX discrimination task in various interstimulus intervals (1ST) as a within-subject factor. Speech stimuli were synthesized to comprise both typical and atypical stimulus sets. In the typical set, the standard stimulus had characteristics of the typical Japanese /aba/ sound. In the atypical set, the standard was not a good exemplar of the Japanese /aba/ sound although it was usually recognized as /aba/. The performance of the subjects was analyzed in terms of both the center and width of discriminal processes. Even at relatively short ISIs, there was a tendency for the typical standard to have a smaller width score than the atypical standard, suggesting that the perceptual identity of the typical stimulus was higher than that of the atypical stimulus. At long ISIs, the effect of the typicality became less salient. The estimation of the center of discriminal processes indicated that perceptual distance along the stimulus continuum is asymmetrical and that the direction of the asymmetry was different between the typical and atypical condition. This partially supports the idea of the perceptual magnet. Because the effect of ISI was completely different from what has been observed in previous studies on the categorical perception, this paradigm could seize a new aspect of the influence of knowledge on perception. The results indicate that the differentiation by the prototypes for phoneme classes occurs at an early stage of perception.

Full Paper

Bibliographic reference.  Tsuzaki, Minoru (1992): "Effects of typicality and interstimulus interval on the discrimination of speech stimuli: within-subject comparison", In ICSLP-1992, 1083-1086.