Angela L. Bauman
Dept. of Psychol., SUNY-Buffalo, Park Hall, Box 604110, Buffalo, NY 14260-4110
Judith C. Goodman
Univ. of California at San Diego, La Jolla, CA 92093
Adults and children use lexical knowledge to interpret phonemes in speech [W. F. Ganong, JEP: HPP 6, 110--125 (1980); Hurlburt and Goodman, in preparation; S. Nittrouer and A. Boothroyd, J. Acoust. Soc. Am. 87, 2705--2715 (1990)]. This study examines the nature of lexical representations necessary for top-down effects. In a baseline assessment, 5-year-olds and adults heard stimuli from seven-step voice onset time (VOT) continua. The continua endpoints formed nonwords (e.g., beb->peb). Subjects were then trained on one endpoint from each continuum in one of two learning conditions. Subjects in the exposure condition heard items in a carrier phase five times (e.g., ``The sound you will hear is peb.''). Subjects in the concept condition heard five instances of each item used as a picture label, in definitional sentences, and in a sentence identifying its superordinate category. After training, subjects again heard the baseline VOT continua. Children's and adults' phoneme boundaries shifted such that a greater proportion of tokens were perceived as compatible with the trained end of the continuum regardless of learning condition. This suggests that minimal exposure to a sound pattern, rather than fully-specified lexical knowledge, can result in top-down effects in speech perception.