The cognitive neuroscience of signed language: Applications to a working memory system for sign and speech
The current chapter is about the scientiﬁc value of using sign language as a tool for understanding the interaction between language and cognition. Diﬀerences in sensory input channels between sign language and spoken language (visuospatial vs. auditory/audiovisual) and diﬀerences in the means of articulating the language (manual vs. oral) represent sensory and motor aspects of the languages that may contribute to disentangling neural substrates that are either shared or unique for several levels of comparative cognitive and communicative analysis. We will show that signed language may be proﬁtably used to uncover behavioural and neural similarities and diﬀerences between the cognitive and neural bases of languages in diﬀerent modalities. In particular, we focus on using sign language as a tool for testing critical assumptions about a working memory system for ease of language understanding. Since the linguistic status of sign language has been questioned – for example, in the debate about oral or manual methods of teaching the deaf (e.g., Smith & Campbell, 1997; Öhngren, 1992) – we commence our discussion by examining the evidence supporting this status and justifying the use of sign language as a tool for scrutinizing cognitive functions.