Mesch, J., & Schönström, K. (2021). Use and acquisition of mouth actions in L2 sign language learners : A corpus-based approach. Sign Language and Linguistics, 4(1). 
https://doi.org/10.1075/sll.19003.mes

About the study

Based on longitudinal data from an L2 learner corpus, we describe the distribution, frequency, and spreading patterns of mouth actions in sixteen L2 learners at two time points. The data are compared with nine signers of an L1 control group.

The results reveal some differences in the use of mouth actions between the groups. The results are specifically related to the category of mouthing borrowed from spoken Swedish. L2 signers show an increased use of mouthing compared to L1 signers. Conversely, L1 signers exhibit an increased use of reduced mouthing compared with L2 signers. We also observe an increase of adverbial mouth gestures within the L2 group. The results are discussed in relation to previous findings, and within the framework of cross-linguistic influence.