Recursion in Nicaraguan Sign Language

Syntactic recursion is argued to be a key property of natural languages, allowing us to create an infinite number of utterances from a finite number of words and rules. Some have argued that recursion is uniquely human. There are at least two possibilities for the origins of recursion: 1) Recursion is a property of the language faculty. 2) Recursion is an historical accomplishment and is culturally constructed over millennia. Here we ask whether an emerging sign language, Nicaraguan Sign Language (NSL), exhibits syntactic recursion by comparing the language of the first three age cohorts of signers. Signers (n=27) watched and described vignettes designed to elicit relative clauses. Results suggest that signers from all three cohorts have strategies to fulfill the discourse function of relative clauses, picking out an individual from a set. The grammatical form of the utterances differs across cohorts, with signers from later cohorts clearly producing embedded structures.