To linguistically represent and encode the visual world (i.e., to talk about what we see) requires a crucial interface between language and spatial cognition. Signed languages can provide unique insight into this interface because physical space is used directly to encode linguistic and spatial relations. American Sign Language (ASL) differs from spoken languages in that it is expressed with the hands in space and perceived by the visual system. Thus, ASL also presents an opportunity to explore how the modality in which a language is conveyed affects the nature of grammatical encoding (e.g., how languages express different linguistic relations) and the nature of language processing (how people interpret and produce language in real time). Currently, very little is known about language processing in ASL, and the proposed studies will be some of the first to investigate how a visual language is perceived and understood on-line. The studies explore the ramifications of using space for expressing linguistic contrasts in referential and spatial domains. Specifically, the experiments focus on the use of space to express coreference relations, frames of reference, and spatial information. The major goal of the research is to explore the grammaticization of space in sign language and its impact on language processing. The project contains two primary lines of inquiry: 1) on-line tracking of spatial anaphora and 2) the use of space to represent space. The first group of experiments explore how signers understand and maintain the association between referents and their spatial loci during real time processing. The results of these experiments will provide insight into the nature of the processing mechanisms required for sign language and will help determine what aspects of referential processing hold across language modalities. The second line of experiments investigate the consequences of using space to represent space by investigating how deaf signers create spatia l mental models from signed discourse, how signers chose a spatial reference frame, and how signers integrate physical signing space with a mental representation of space. These experiments will illuminate how physical space is manipulated linguistically to communicate locative information and will clarify how such spatial structure is interpreted during processing. Together, these results will elucidate the nature of the interface between language and spatial cognition.