A duration-dependent account of coarticulation for hyper- and hypoarticulation

Previous studies investigating anticipatory coarticulation in emphatically stressed CV sequences and during fast speaking rates reported that three factors contributed to the overall extent of the documented coarticulation. These factors were: (1) vowel identity, (2) vowel space expansion (emphasis) or reduction (fast rate), and a hypothesized (3) 'deeper' and 'shallower' stop closure contact in emphatic and faster speech, respectively. The objective of the current research was to conceptually and quantitatively unify these two studies. This was accomplished by showing that the opposite changes to frequency onsets of F2 transitions due to emphatic and rapid speech systematically vary as a function of the durational changes in the stop closure interval. Specifically, the decrease in coarticulation in emphatic speech is characterized by increases in F2 onsets and longer stop closures (relative to a normal baseline); the increase in coarticulation due to rapid speech shows concomitant decreases in F2 onsets coinciding with shorter stop closure intervals. Vocal tract area function simulations corresponding to emphatic and reduced speech implicitly support 'deeper' and 'shallower' closure contacts as a third factor contributing to the overall extent of anticipatory CV coarticulation.