Early vocabulary development in deaf native signers: a British Sign Language adaptation of the communicative development inventories.

BACKGROUND: There is a dearth of assessments of sign language development in young deaf children. This study gathered age-related scores from a sample of deaf native signing children using an adapted version of the MacArthur-Bates CDI (Fenson et al., 1994). METHOD: Parental reports on children's receptive and expressive signing were collected longitudinally on 29 deaf native British Sign Language (BSL) users, aged 8-36 months, yielding 146 datasets. RESULTS: A smooth upward growth curve was obtained for early vocabulary development and percentile scores were derived. In the main, receptive scores were in advance of expressive scores. No gender bias was observed. Correlational analysis identified factors associated with vocabulary development, including parental education and mothers' training in BSL. Individual children's profiles showed a range of development and some evidence of a growth spurt. Clinical and research issues relating to the measure are discussed. CONCLUSIONS: The study has developed a valid, reliable measure of vocabulary development in BSL. Further research is needed to investigate the relationship between vocabulary acquisition in native and non-native signers.

Language and imagery: effects of language modality.

Across spoken languages, properties of wordforms (e.g. the sounds in the word hammer) do not generally evoke mental images associated to meanings. However, across signed languages, many signforms readily evoke mental images (e.g. the sign HAMMER resembles the motion involved in hammering). Here we assess the relationship between language and imagery, comparing the performance of English speakers and British sign language (BSL) signers in meaning similarity judgement tasks. In experiment 1, we found that BSL signers used these imagistic properties in making meaning similarity judgements, in contrast with English speakers. In experiment 2, we found that English speakers behaved more like BSL signers when asked to develop mental images for the words before performing the same task. These findings show that language differences can bias users to attend more to those aspects of the world encoded in their language than to those that are not; and that language modality (spoken versus signed) can affect the degree to which imagery is involved in language.

Siblings and theory of mind in deaf native signing children.

We report a study designed to examine the basis of "theory of mind" (ToM) reasoning in deaf children who are native signers of British Sign Language. The participants were 20 native signers (aged 4-8 years) and their siblings. The children were given a measure of the quality of sibling relations together with a referential communication test concerning physical representations of objects and people. Sibling quality as perceived by siblings predicted children's ToM scores over and above age and referential communication. We conclude that the process of ToM understanding is linked to positive sibling relations that may permit access to knowledge about the inner worlds of beliefs and other mental states.

Signposts to development: theory of mind in deaf children.

Possession of a "theory of mind" (ToM)--as demonstrated by an understanding of the false beliefs of others--is fundamental in children's cognitive development. A key question for debate concerns the effect of language input on ToM. In this respect, comparisons of deaf native-signing children who are raised by deaf signing parents with deaf late-signing children who are raised by hearing parents provide a critical test. This article reports on two studies (N = 100 and N = 39) using "thought picture" measures of ToM that minimize verbal task-performance requirements. These studies demonstrated that even when factors such as syntax ability, mental age in spatial ability, and executive functioning were considered, deaf late signers still showed deficits in ToM understanding relative to deaf native signers or hearing controls. Even though the native signers were significantly younger than a sample of late signers matched for spatial mental age and scores on a test of receptive sign language ability, native signers outperformed late signers on pictorial ToM tasks. The results are discussed in terms of access to conversation and extralinguistic influences on development such as the presence of sibling relationships, and suggest that the expression of a ToM is the end result of social understanding mediated by early conversational experience.