Investigating the roles of vocal tract size and phoneme content in context effects
A. Davi Vitela, Andrew J. Lotto · The Journal of the Acoustical Society of America · 2011
In this series of experiments, we examined the role of specific vocal tract and phoneme contextual information on vowel categorization. An articulatory synthesizer was used to create vowels produced by specific vocal tract lengths (VT) of different sizes [Story, J. Acoust. Soc. Am. 117, 3231-3254 (2005)]. Contexts of repeated vowels (/a/ or /i/) produced by long and short VTs preceded a target series that changed perceptually from /bit/-/bet/. If listeners are extracting information about the VT itself, similar context effects should be elicited by either vowels produced by the same VT. If listeners are comparing the ambiguous target to the placement of a known vowel, one might predict similar results for the /aa/ condition or the /ii/. However, a complete cross-over interaction was obtained such that the effect of the context could not be predicted by the VT size or the vowel identity, but instead on the acoustic characteristics of F1. Follow-up experiments used contexts consisting of cross-cutting vowels from both VTs or two different vowels from the same VT. The results suggest that the order of the appended stimuli matters, demonstrating that listeners are not averaging information equally across the entire context. [Work supported by NIH-NIDCD.]