Paul Iverson
Patricia K. Kuhl
Dept. of Speech and Hear. Sci., WJ-10, Univ. of Washington, Seattle, WA 98195
Previous experiments with human adults and infants have demonstrated that variants of the vowel /i/ are more difficult to discriminate from a prototypic /i/ than from a nonprototypic /i/, suggesting that prototypes assimilate neighboring stimuli [P. K. Kuhl, Percept. Psychophys. 50, 93--107 (1991)]. A series of experiments examined this influence of prototypes using multidimensional scaling. Adults discriminated pairs of /i/ tokens and RTs were measured. Multidimensional scaling was used to place the tokens in a Euclidian space where pairs of tokens with long RTs were close in the space and pairs with short RTs were far apart. Tokens were more closely spaced near the prototypic /i/, demonstrating that prototypes assimilate proximate regions of the vowel space. This effect was stronger with long ISIs (2500 ms) than with short ISIs (25 and 250 ms), suggesting that vowel prototypes distort memory for individual tokens. [Work supported by NIH.]