Biological foundations of language: clues from sign language.

The general objective of the research reviewed here is to examine the biological foundations of human language. We report on language and its formal architecture, as well as its representation in the brain, through studying languages that have arisen outside of the mainstream of spoken languages; the visual gestural systems developed among deaf people. The study of sign languages offers a unique opportunity for insight into the nature of neural mechanisms for language, since sign languages utilize a transmission modality different from that of spoken languages. To understand the extent to which neural mechanisms for language are shaped by the modality of their implementation, we are naturally led to the study of sign language because we cannot solve the problem for language in general within the spoken-auditory modality. In these studies, one can make use of the difference in transmission modality between sign and speech to investigate the biological foundations of language. Manual communi-