Cutler, A., & Fear, B. D.
(1991). Categoricality in acceptability judgements for strong versus weak vowels. In J. Llisterri (Ed.), Proceedings of the ESCA Workshop on Phonetics and Phonology of Speaking Styles (pp. 18.1-18.5). Barcelona, Catalonia: Universitat Autonoma de Barcelona.
A distinction between strong and weak vowels can be drawn on the basis of vowel quality, of stress, or of both factors. An experiment was conducted in which sets of contextually matched word-intial vowels ranging from clearly strong to clearly weak were cross-spliced, and the naturalness of the resulting words was rated by listeners. The ratings showed that in general cross-spliced words were only significantly less acceptable than unspliced words when schwa was not involved; this supports a categorical distinction based on vowel quality.