Metaphors we learn to sign by: Positive transfer effects of existing sign language expertise and gestural repertoire on metaphor inferencing in a novel sign language

• Positive transfer of existing sign language expertise and knowledge of modality-specific metaphor formation strategies to metaphor inferencing in a novel sign language. • Role of iconicity: In sign novices, iconicity facilitates the detection of concrete meanings, but its visual saliency may hinder further abstraction to metaphorical meaning. • Results support hybrid approaches to metaphor inferencing considering both universal and conventionalised aspects of metaphors. • Cognate effects generate positive transfer from pre-existing linguistic and gestural representtations. • Impact: L2 metaphor inferencing modulated by existing linguistic knowledge, calling for teaching approaches tailored to learner profiles. Our study investigated metaphor inferencing in second languages (L2). According to universalist accounts, L2 metaphor comprehension should be intuitive. However, cross-linguistic differences suggest that successful metaphor inferencing is subject to transfer effects. Little is known about the interaction of transfer effects involving modality differences in the context of sign languages. We investigated whether existing sign language expertise enhances SPACE-TIME metaphor inferencing in signed L2s. Crucially, we focused on SPACE-TIME metaphor inferencing because the need to abstract from salient concrete SPACE interpretations may pose challenges to sign novices. Methodologically, we compared native signers (N = 27, L1 = American or British Sign Language) to hearing sign novices (N = 37, L1 = English). Participants were exposed to a novel sign language through a short weather forecast, mirroring real-life implicit immersion. Subsequently, they completed tasks tapping into meaning assignment. Our analyses focused on metaphor inferencing, considering transfer effects from cognateness regarding L1-L2 sign similarity and gesture-sign similarity. Our findings revealed a marked dissociation in transfer effects by group. Amongst native signers metaphoricity facilitated L2 meaning assignment. However, metaphoricity posed a challenge to sign novices who defaulted to concrete SPACE interpretations, misled by their saliency and iconicity. At the item-level, cognate effects occurred both from existing linguistic knowledge and gestural repertoires. Our study suggests that whilst all participants recognised universal iconic patterns facilitating concrete meaning assignment, abstraction and metaphor inferencing relied on positive transfer from specific cognates or generic knowledge of modality-specific metaphor formation strategies. Hence, teaching materials should build on existing knowledge in a bespoke manner.