Stimulus ratio effects on speech discrimination by children and adults.
This investigation examined the response strategies and discrimination accuracy of adults and children aged 5-10 as the ratio of same to different trials was varied across three conditions of a "change/no-change" discrimination task. The conditions varied as follows: (a) a ratio of one-third same to two-thirds different trials (33% same), (b) an equal ratio of same to different trials (50% same), and (c) a ratio of two-thirds same to one-third different trials (67% same). Stimuli were synthetic consonant-vowel syllables that changed along a place of articulation dimension by formant frequency transition. Results showed that all subjects changed their response strategies depending on the ratio of same-to-different trials. The most lax response pattern was observed for the 50% same condition, and the most conservative pattern was observed for the 67% same condition. Adult response patterns were most conservative across condition. Difference in discrimination accuracy as measured by P(C) were found, with the largest difference in the 5- to 6-year-old group and the smallest change in the adult group. These findings suggest that children's response strategies, like those of adults, can be manipulated by changing the ratio of same-to-different trials. Furthermore, interpretation of sensitivity measures must be referenced to task variables such as the ratio of same-to-different trials.
Sussman
J E
JE
State University of New York, Department of Communicative Disorders and Science, Faculty of Social Sciences, Buffalo 14260.
D000161:Acoustic Stimulation; D000328:Adult; D000367:Age Factors; D000375:Aging / Q000502:physiology*; D015982:Bias; D002648:Child; D002675:Child, Preschool; D006801:Humans; D007858:Learning; D010700:Phonetics; D013063:Speech Discrimination Tests; D013067:Speech Perception / Q000502:physiology*