The effect of prosodic weakening on the production and perception of trans-consonantal vowel coarticulation in German.

The present study considers whether coarticulation in production and its relationship to categorization could provide a synchronic basis for the prevalence of sound change in unstressed syllables. The size of V2-on-V1 coarticulation in the production of /pV1pV2l/ non-words (V1 = /U,Y/ and V2 = /e, o/) produced by German speakers and with stress falling either on the first or second syllable was compared with forced-choice perceptual categorization of resynthesized versions of these non-words. In speech production, /Y/ but not /U/ was perturbed by anticipatory V2-on-V1 coarticulation. Stress had no influence on coarticulation but caused target undershoot in /U/. The same speakers compensated for coarticulation in perception: however, in the unstressed context the speakers compensated less and their diminished compensatory coarticulation was shown to be linked to /U/-undershoot. Taken together, these results point to a mismatch between coarticulation and categorization that is suggested as a possible source of sound change: whereas de-stressing did not affect V2-on-V1 coarticulation in production, it weakened V2's influence on perceptual /ʊ-Y/ categorization. The evidence that this mismatch is indirectly caused by stress-dependent reduction in /U/ that is unrelated to the V2-source of the coarticulation is also consistent with a model of sound change as non-teleological.