ABSTRACT
Evidence from the acquisition of spoken language has fuelled centuries of debate on the biological bases of language behavior. But language may be acquired through more than one modality. Sign language is acquired in a visual-spatial modality, and as evidence from the course of acquisition of sign languages becomes increasingly available it is possible to ask what parts of language acquisition are modality-general and what aspects are specific to speech or sign. Data on the influence of modality on language acquisition provides important new insights and makes further progress in elucidating the relationship of biology to language behavior.
