The heritability of vocal tract structures estimated from structural MRI in a large cohort of Dutch twins.

While language is expressed in multiple modalities, including sign, writing, or whistles, speech is arguably the most common. The human vocal tract is capable of producing the bewildering diversity of the 7000 or so currently spoken languages, but relatively little is known about its genetic bases, especially in what concerns normal variation. Here, we capitalize on five cohorts totaling 632 Dutch twins with structural magnetic resonance imaging (MRI) data. Two raters placed clearly defined (semi)landmarks on each MRI scan, from which we derived 146 measures capturing the dimensions and shape of various vocal tract structures, but also aspects of the head and face. We used Genetic Covariance Structure Modeling to estimate the additive genetic, common environmental or non-additive genetic, and unique environmental components, while controlling for various confounds and for any systematic differences between the two raters. We found high heritability, h2, for aspects of the skull and face, the mandible, the anteroposterior (horizontal) dimension of the vocal tract, and the position of the hyoid bone. These findings extend the existing literature, and open new perspectives for understanding the complex interplay between genetics, environment, and culture that shape our vocal tracts, and which may help explain cross-linguistic differences in phonetics and phonology.

Being a heritage speaker matters: the role of markedness in subject-verb person agreement in Italian.

This study examines online processing and offline judgments of subject-verb person agreement with a focus on how this is impacted by markedness in heritage speakers (HSs) of Italian. To this end, 54 adult HSs living in Germany and 40 homeland Italian speakers completed a self-paced reading task (SPRT) and a grammaticality judgment task (GJT). Markedness was manipulated by probing agreement with both first-person (marked) and third-person (unmarked) subjects. Agreement was manipulated by crossing first-person marked subjects with third-person unmarked verbs and vice versa. Crucially, person violations with 1st person subjects (e.g., io *suona la chitarra "I plays-3rd-person the guitar") yielded significantly shorter RTs in the SPRT and higher accuracy in the GJT than the opposite error type (e.g., il giornalista *esco spesso "the journalist go-1st-person out often"). This effect is consistent with the claim that when the first element in the dependency is marked (first person), the parser generates stronger predictions regarding upcoming agreeing elements. These results nicely align with work from the same populations investigating the impact of morphological markedness on grammatical gender agreement, suggesting that markedness impacts agreement similarly in two distinct grammatical domains and that sensitivity to markedness is more prevalent for HSs.

Effects of markedness in gender processing in Italian as a heritage language: A speed accuracy tradeoff.

This study examined potential sources of grammatical gender variability in heritage speakers (HSs) of Italian with a focus on morphological markedness. Fifty-four adult Italian HSs living in Germany and 40 homeland Italian speakers completed an online Self-Paced Reading Task and an offline Grammaticality Judgment Task. Both tasks involved sentences with grammatical and ungrammatical noun-adjective agreement, manipulating markedness. In grammatical sentences, both groups showed a markedness effect: shorter reading times (RTs) and higher accuracy for sentences containing masculine nouns as compared to sentences with feminine nouns. In ungrammatical sentences, although both groups were sensitive to ungrammaticality, only HSs showed a markedness effect, that is, they had significantly longer RTs and higher accuracy when violations were realized on feminine adjectives. Proficiency in the HL was a significant predictor of accuracy and RTs at the individual level. Taken together, results indicate that HSs acquire and process gender in a qualitatively similar way to homeland native speakers. However, RT evidence seems to suggest that at least under particular experimental methods, markedness considerations are more prevalent for HSs resulting in a speed-accuracy tradeoff.