Schwa has an articulatory target in American English

Is American English schwa’s position determined solely by coarticulatory pressures? There is currently disagreement between articulation-based and acoustic-based studies (Browman and Goldstein 1994; Flemming 2009). In two acoustic corpus studies using the Switchboard and Buckeye corpora, we find that vowels head toward a central high vowel position when subject to increased coarticulatory pressures, rather than toward the position occupied by American English schwa. Even lexical schwa vowels shift to lower F1 values when their duration is relatively short. Our findings are consistent with schwa occupying a perceptually but not articulatorily neutral position. As such, they bear on vowel neutralization patterns, and suggest that unstressed syllables may convey specific information: that they are not stressed.