The development of prosodic features and their contribution to rhythm production in simultaneous bilinguals

This study aims to analyse facilitatory and inhibitory effects of bilingualism on the acquisition of prosodic features, and their contribution to speech rhythm. Here, we concentrate on phrase-final lengthening and accentuation, prosodic features suggested to give rise to different rhythmic percepts even when syllable structure is kept constant across languages. In particular, we investigate whether the development of these two features in Spanish-English simultaneous bilinguals correlates with rhythm development. Our results demonstrate that, as is the case for bilingual rhythm development overall the development of prosodic head- and edge-marking suggests that the two languages are rhythmically separable from around the age of 4, with clearly separate rhythms at the age of 6. Additionally, we can confirm that bilinguals also start out with an even-timed bias in the development of final lengthening and accentuation as reflected by fewer durational differentiations between prosodic syllable types. Furthermore, we can observe the same advantages in bilingual prosodic acquisition in the structurally more complex language that were found in rhythm development. These advantages are manifested by the earlier mastery of robust durational differentiations between syllable types to an adult-like extent. Finally, the comparison with monolingual data demonstrates that bilinguals do, in fact, have an advantage in their development in comparison with monolinguals. We hypothesise that this advantage is borne out of more advanced motor control and possibly more stable mental representations as a result of the dual language input, and dual language production experience.