Magdalene H. Chalikia
Natasha Parvey
Dept. of Psych., Moorhead State Univ., Moorhead, MN 56563
Previous studies show that listeners who are presented with a repeated sequence of steady state vowels (between 30--100 ms each) report hearing illusory changes in the identity of the speech sounds, a phenomenon called phonemic transformations [M. H. Chalikia and R. M. Warren, Lang. Speech 34, 109--143 (1991)]. The organizations are pretty salient and can be recognized at a later time. In previous studies all vowels were initially at the same duration. In this study, the vowels within a sequence had different durations (baseline stimuli), to resemble characteristics of real speech utterances. The effects of manipulating systematically the duration of individual vowels by increasing or decreasing the duration of each vowel relative to the baseline is investigated. Twenty-six subjects were asked to listen to the baseline stimuli and record what they heard with each. Then, they were asked to match each of the additional vowel sequences to the forms heard with the baseline ones. Matching performance decreased for the short durations (10--60 ms/vowel), but not for the longer ones (40--180 ms/vowel).