"At a neurological level, Sign is a language and is treated as such by the brain, even though it is visual rather than auditory, and spatially rather than sequentially organised. And as a language, it is processed by the left hemisphere of the brain, which is biologically specialised for just this function.

      The fact that Sign is based here in the left hemisphere despite its spatial organisation, suggests that there is a representation of 'linguistic' space in the brain completely different from that of ordinary, 'topographic' space. Bellugi provides a remarkable and startling confirmation of this."

- Seeing Voices