To investigate language and its formal architecture, as well as its represen­ tation in the brain, in this chapter we examine properties of languages in different modalities (spoken and signed). Research over the past decade has specified the ways in which the formal properties of languages are shaped by their modalities of expression, sifting properties peculiar to a particular language mode from more general properties common to all languages (Bellugi, 1988; Bellugi & Klima, 1982; Klima & Bellugi, 1979). American Sign Language (ASL) exhibits formal structuring at the same levels as spoken languages and similar kinds of organizational principles (con­ strained systems of features, rules based on underlying forms, recursive grammatical processes). Yet research shows that at all structural levels, the form of an utterance in a signed language is deeply influenced by the modality in which the language is cast (Bellugi, 1980).