How Spoken and Signed Language Structure Space Differently: a Neural Model

Linguistic research to date has determined many of the factors that govern the structure of the spatial schemas found across spoken languages. We can now integrate these factors and propose the comprehensive system they comprise for spatial structuring in spoken language. This system is characterized by several features. At a componential level, it has a relatively closed universally available inventory of fundamental spatial elements. These elements group into a relatively closed set of spatial categories. And each category includes only a relatively closed small number of particular elements: the spatial distinctions that each category can ever mark. At a composite level, elements of the inventory combine in particular arrangements to form whole spatial schemas. Each language has a relatively closed set of "pre-packaged" schemas of this sort. Finally, the system includes a set of processes that can extend or deform pre-packaged schemas and thus enable a language's particular set of schemas to be applied to a wider range of spatial structures.

An examination of signed language shows that its structural representation of space systematically differs from that in spoken language in the direction of what appear to be the structural characteristics of scene parsing in visual perception. Such differences include the following features. Signed language can mark finer spatial distinctions with its inventory of more structural elements, more categories, and more elements per category. It represents many more of these distinctions in any particular expression. It represents these distinctions independently in the expression, not bundled together into pre-packaged schemas. And its spatial representations are largely iconic with visible spatial characteristics.

The findings suggest that instead of some discrete whole-language module, as proposed by Fodor and Chomsky, spoken language and signed language are both based on some more limited core linguistic system that then connects with different further subsystems for the full functioning of the two different language modalities. These findings have implications for the evolution of language.