Kathryn Mason

Identifying specific language impairment in deaf children acquiring British Sign Language: Implications for theory and practice

This paper presents the first ever group study of specific language impairment (SLI) in users of sign language. A group of 50 children were referred to the study by teachers and speech and language therapists. Individuals who fitted pre-determined criteria for SLI were then systematically assessed. Here, we describe in detail the performance of 13 signing deaf children aged 5-14 years on normed tests of British Sign Language (BSL) sentence comprehension, repetition of nonsense signs, expressive grammar and narrative skills, alongside tests of non-verbal intelligence and fine motor control. Results show these children to have a significant language delay compared to their peers matched for age and language experience. This impaired development cannot be explained by poor exposure to BSL, or by lower general cognitive, social, or motor abilities. As is the case for SLI in spoken languages, we find heterogeneity within the group in terms of which aspects of language are affected and the severity of the impairment. We discuss the implications of the existence of language impairments in a sign language for theories of SLI and clinical practice.

The Acquisition of Sign Language: The Impact of Phonetic Complexity on Phonology

Research into the effect of phonetic complexity on phonological acquisition has a long history in spoken languages. This paper considers the effect of phonetics on phonological development in a signed language. We report on an experiment in which nonword-repetition methodology was adapted so as to examine in a systematic way how phonetic complexity in two phonological parameters of signed languages — handshape and movement — affects the perception and articulation of signs. Ninety-one Deaf children aged 3–11 acquiring British Sign Language (BSL) and 46 hearing nonsigners aged 6–11 repeated a set of 40 nonsense signs. For Deaf children, repetition accuracy improved with age, correlated with wider BSL abilities, and was lowest for signs that were phonetically complex. Repetition accuracy was correlated with fine motor skills for the youngest children. Despite their lower repetition accuracy, the hearing group were similarly affected by phonetic complexity, suggesting that common visual and motoric factors are at play when processing linguistic information in the visuo-gestural modality.

Deaf children's non-verbal working memory is impacted by their language experience

Several recent studies have suggested that deaf children perform more poorly on working memory tasks compared to hearing children, but these studies have not been able to determine whether this poorer performance arises directly from deafness itself or from deaf childrens reduced language exposure. The issue remains unresolved because findings come mostly from (1) tasks that are verbal as opposed to non-verbal, and (2) involve deaf children who use spoken communication and therefore may have experienced impoverished input and delayed language acquisition. This is in contrast to deaf children who have been exposed to a sign language since birth from Deaf parents (and who therefore have native language-learning opportunities within a normal developmental timeframe for language acquisition). A more direct, and therefore stronger, test of the hypothesis that the type and quality of language exposure impact working memory is to use measures of non-verbal working memory (NVWM) and to compare hearing children with two groups of deaf signing children: those who have had native exposure to a sign language, and those who have experienced delayed acquisition and reduced quality of language input compared to their native-signing peers. In this study we investigated the relationship between NVWM and language in three groups aged 6–11 years: hearing children (n = 28), deaf children who were native users of British Sign Language (BSL; n = 8), and deaf children who used BSL but who were not native signers (n = 19). We administered a battery of non-verbal reasoning, NVWM, and language tasks. We examined whether the groups differed on NVWM scores, and whether scores on language tasks predicted scores on NVWM tasks. For the two executive-loaded NVWM tasks included in our battery, the non-native signers performed less accurately than the native signer and hearing groups (who did not differ from one another). Multiple regression analysis revealed that scores on the vocabulary measure predicted scores on those two executive-loaded NVWM tasks (with age and non-verbal reasoning partialled out). Our results suggest that whatever the language modality—spoken or signed—rich language experience from birth, and the good language skills that result from this early age of acquisition, play a critical role in the development of NVWM and in performance on NVWM tasks.

Sentence Repetition in Deaf Children with Specific Language Impairment in British Sign Language.

Children with specific language impairment (SLI) perform poorly on sentence repetition tasks across different spoken languages, but until now, this methodology has not been investigated in children who have SLI in a signed language. Users of a natural sign language encode different sentence meanings through their choice of signs and by altering the sequence and inflections of these signs. Grammatical information is expressed through movement and configurational changes of the hands and face. The visual modality thus influences how grammatical morphology and syntax are instantiated. How would language impairment impact on the acquisition of these types of linguistic devices in child signers? We investigated sentence repetition skills in a group of 11 deaf children who display SLI in British Sign Language (BSL) and 11 deaf controls with no language impairment who were matched for age and years of BSL exposure. The SLI group was significantly less accurate on an overall accuracy score, and they repeated lexical items, overall sentence meaning, sign order, facial expressions, and verb morphological structures significantly less accurately than controls. This pattern of language deficits is consistent with the characterization of SLI in spoken languages even though expression is in a different modality. We conclude that explanations of SLI, and of poor sentence repetition by children with this disorder, must be able to account for both the spoken and signed modalities.

Deficits in narrative abilities in child British Sign Language users with specific language impairment.

This study details the first ever investigation of narrative skills in a group of 17 deaf signing children who have been diagnosed with disorders in their British Sign Language development compared with a control group of 17 deaf child signers matched for age, gender, education, quantity, and quality of language exposure and non-verbal intelligence. Children were asked to generate a narrative based on events in a language free video. Narratives were analysed for global structure, information content and local level grammatical devices, especially verb morphology. The language-impaired group produced shorter, less structured and grammatically simpler narratives than controls, with verb morphology particularly impaired. Despite major differences in how sign and spoken languages are articulated, narrative is shown to be a reliable marker of language impairment across the modality boundaries.