The general objective of our research is to study the biological foundations of human language. We aim to investigate language and its formal architecture, as well as its representation in the brain, by studying languages which have arisen outside of the mainstream of spoken languages, the visual-gestural language of deaf people. For the form of its grammatical devices, the modality in which a language develops makes a crucial difference. Multi-layering of linguistic elements and the use of space in the service of syntax appear to be modality-determined aspects of sign language. One of the central issues in the renewal grant is the consequences of the differing capacities of visual and auditory processing on the form that language takes and thereby on the nature of mental representations involving language, and on the nature of language representation in the brain. We proceed along three major lines of inquiry: 1) We investigate linguistic and modality determinants of perception through the computergraphic presentation of movement isolated from sign forms. We analyze the psychological representations of human movement and the effect on that representation when movement constitutes part of a linguistic system. We then turn to spatial vs. temporal processing and examine mental representations of sign language syntax. 2) To assess the generality of the putative modality-determined characteristics of visual-gestural languages, we propose structual and psycholinguistic studies of Chinese Sign Language, a sign language completely unrelated to American Sign Language. We combine these cross-linguistic studies with studies of the structure and processing of Chinese characters, a script which, like sign, puts heavy emphasis on visual-spatial processing. 3) Finally, we investigate the nature of hemispheric specialization for language by pitting physical form against linguistic function for language in another modality.