Which aspects of visual motivation aid the implicit learning of signs at first exposure?

We investigated whether sign-naïve learners can infer and learn the meaning of signs after minimal exposure to continuous, naturalistic input in the form of a weather forecast in Swedish Sign Language. Participants were L1-English adults. Two experimental groups watched the forecast once (N=40) or twice (N=42); a control group did not (N=42). Participants were then asked to assign meaning to 22 target signs. We explored predictors of meaning assignment with respect to item occurrence frequency and three facets of visual-motivation: iconicity, transparency, and gesture similarity. Meaning assignment was enhanced by exposure and item frequency, thereby providing evidence for implicit language learning in a new modality, even under challenging naturalistic conditions. Accuracy was also contingent upon iconicity and transparency, but not upon gesture similarity. Meaning assignment at first exposure is thus visually-motivated, although the overall low accuracy rates and further qualitative analyses suggest that visually-motivated meaning assignment is not always successful.