The general objective of our research is to study the human capacity for language. We aim to investigate to what extent the overall form and organization of language is determined by the articulatory and perceptual modality in which it has developed and to what extent they represent more fundamental aspects of human cognition. As a research tool we study American Sign Language, the system of hand signs developed by deaf people in the absence of speech. We find that ASL differs dramatically from English and other spoken languages in some of the mechanisms by which its lexical units are modified. For the form of its inflectional and derivational processes the mode in which the language develops makes a crucial difference. The primary focus of the present grant is to bring psycholinguistic evidence to bear on an understanding of the structural properties of a language in a differenct mode. We propose some experimental investigations of the morphology of ASL, bringing into relief the interplay between cognitive processing and linguistic form, addressing specific issues not only relevant to the ways deaf signers process morphological forms in ASL but, more generally, relevant to theories of the perception of speech and to theories of the representation of language in the brain. We proceed along four major lines of inquiry. 1) We first explore whether signers encode modulated forms separately in terms of their component morphemes even through lexical and grammatical elements are simultaneously encoded in a sign form. 2) We then address whether signers utilize modulatory features, such as those that have emerged from our linguistic analysis, during the perception and memory of modulatory forms. 3) We further begin exploration of the virtually uncharged area of the phonetics of modulatory movement. We aim to uncover physical correlates that are sufficient for the perception of proposed featural distinctions. This research will allow us for the first time to adequately address the issue of categorical perception for changes along temporal dimensions of ASL modulations. 4) We propose studies on whether processing of certain modulatory features is categorical, as has been found for many speech sounds, or is continuous, as is the case for most psychological continuations. Finally, we examine cerebral asymmetries for specifically grammatical processing of ASL modulations, prov (Text Truncated - Exceeds Capacity)