Ann Senghas: Barnard College of Columbia University, Dept. of Psychology

The recent emergence of a new sign language among deaf children and adolescents in Nicaragua provides an opportunity to study how linguistic features of a language arise and spread. New features that arise must be successfully transmitted from one generation to the next to survive as part of the language. During this transmission, language form is shaped by both the characteristics of ontogenetic development within individual users and by historical changes in patterns of interaction between users. To capture this process, changes over the past 25 years will be examined within two domains: expressions of manner and path of movement, and expressions of spatial co-reference. These data reveal that, as the new language is learned, holistic and analog expressions are being replaced by discrete, combinatorial expressions. It appears that these new form-function mappings arise among child learners who functionally differentiate previously equivalent forms. The new mappings are then acquired by their age peers (while children), and by subsequent generations of children who learn the language, but not by adult contemporaries. As a result, language emergence is characterized by a convergence on form within each age cohort, and a systematic mismatch in form from one age cohort to the cohort that follows. In this way, each age cohort, in sequence, systematically transforms the language environment for the next, enabling each new cohort of learners to develop further than its predecessors.