Can sign-naive adults learn about the phonological regularities of an unfamiliar sign language from minimal exposure?

Adults can extract phonological regularities from just several minutes’ exposure to naturalistic input of an unknown spoken language (Gullberg et al., 2010). We examined whether such implicit statistical learning mechanisms also operate in the sign language modality. The input materials consisted of a continuous sign stream in the form of a weather forecast in Svenskt Teckenspråk (STS). L1-speakers of English with no prior knowledge of a sign language were assigned to two experimental groups who watched the forecast once (N=43) or twice (N=38), and a control group who did not watch it (N=40). Participants completed a ‘surprise’ lexical decision task designed to tap into their awareness of the phonological properties of the core STS lexicon. They viewed individual signs and indicated whether or not these could be real STS signs. The signs comprised four sets: STS signs that (1) were presented, and (2) were not presented, in the forecast; and signs that are not STS signs and (3) contain handshapes outside the STS handshape inventory, and (4) contain sets of phonological features that are dispreferred across sign languages. We found no evidence of any learning of STS phonological regularities. Considered in conjunction with two companion studies which did demonstrate some learning of sign forms and their meanings from these same input materials, our findings suggest limits to what can be learnt after just a few minutes of implicit and naturalistic exposure to language in an unfamiliar modality: information about specific lexical items is learnable, but information that requires generalisation across items may require greater amounts, or a different quality, of input.