Three basic models of vowel inherent spectral change have been proposed: onset + offset, onset + direction, and onset + slope (or spectral rate of change). Morrison (2013) presents three theoretical stimuli whose identification rates relative to each other should lend weight to one of these hypotheses: (i) canonical duration and canonical onset-to-offset trajectory, (ii) canonical duration with double trajectory length, and (iii) canonical trajectory with half duration. The bulk of previous work supports onset + offset. In the present study, eight English monophthongs were synthesized with the Klatt synthesizer of the Berkeley Phonetics Machine. Three versions of each vowel were synthesized, corresponding to the theoretical stimuli of Morrison (2013). These 24 stimuli were used in two studies (n= 18 for each). First was a vowel identification task, where the choices were [hVd] words with the chosen vowels ( heed, hid, etc.). Second was a goodness rating task with a 7-point Likert scale, where participants were played a vowel stimulus while being shown the orthographic [hVd] word containing that vowel. The results do not fully support any one theory, but they align most closely with the onset + direction hypothesis, with onset + offset also being supported.

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