Mouthing in comprehension of multimodal multilingual units in Norwegian Sign Language

Mouthings -- mouth movements that mimic spoken language words produced alongside signing -- are a unique multimodal phenomenon in that they recruit resources from a second language; however, they have not received much attention in research that explicitly frames itself as multimodal. In Norwegian Sign Language (NSL/NTS), the role of mouthing in comprehension has not been studied extensively from the perspective of deaf users of the language. In this study, we add to these two understudied areas by exploring mouthings in comprehension of Norwegian Sign Language in an unrestricted lexical identification paradigm (N=30). We find that when manual forms are polysemous, plausible mouthings improve accuracy in lexical identification and the certainty of comprehension. When mouthings are implausible, it appears that the dominant strategy is to make identification decisions based on the manual form only. In a smaller number of cases participants appeared to rely solely on the mouthing or blended the mouthing and manual components.