Duration as an acoustic cue of the Spanish tap-trill contrast according to age and language background

Previous research has shown that US Spanish heritage speakers produce the tap-trill contrast with varying manners of articulation and a non-canonical number of occlusions, while using duration as a more robust cue to the contrast. This contrast is present in Spanish, the heritage language, and absent in English, the majority language. In this paper, we examine the development of duration as an acoustic correlate of the tap-trill contrast by analyzing semi-spontaneous productions from child and adult heritage speakers as well as age-matched Spanish speakers from a monolingual environment. The durations of phonetic taps and trills were fitted to Bayesian hierarchical models to examine how these speaker groups differ with respect to their use of duration as an acoustic correlate. The results of our analysis show that the average child heritage speaker produces a smaller durational contrast with increased variability, and that some child heritage speakers show near-complete overlap in the duration of the two segments. Adult heritage speakers demonstrate a reduced difference in the tap-trill contrast when compared to Spanish speakers raised in a monolingual environment, but maintain a contrast between the two sounds. Developmental analyses within the child groups do not show significant differences in trill duration by age, but child Spanish monolinguals show a non-linear reduction in tap duration by age that does not occur for heritage children. Overall, our results support a scenario of protracted development in heritage children for the tap-trill contrast, as well as a potential sound change in progress for US Spanish.