Stimulus order effects in vowel discrimination.
In same-different discrimination tasks employing isolated vowel sounds, subjects often give significantly more "different" responses to one order of two stimuli than to the other order. Cowan and Morse [J. Acoust. Soc. Am. 79, 500-507 (1986)] proposed a neutralization hypothesis to account for such effects: The first vowel in a pair is assumed to change its quality in memory in the direction of the neutral vowel, schwa. Three experiments were conducted using a variety of vowels and some initial support for the hypothesis was obtained, using a large stimulus set, but conflicting evidence with smaller stimulus sets. Rather than becoming more similar to schwa, the first vowel in a pair seems to drift toward the interior of the stimulus range employed in a given test. Several possible explanations are discussed for this tendency and its relation to presentation order effects obtained in other psychophysical paradigms is noted.
Repp
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BH
Haskins Laboratories, New Haven, Connecticut 06511-6695.
Crowder
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RG
D000328:Adult; D001288:Attention; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D010153:Paired-Associate Learning; D010700:Phonetics; D013067:Speech Perception