Birth of a Language in the Backlands of Brazil.

It is assumed that in order to acquire a language, children must be exposed to a language during the critical period, which generally lasts until puberty. Here, we report on Cena, an emergent sign language that has developed among a small group of deaf people in an isolated town in the state of Piauí, Brazil. Starting three generations ago, it has developed into a fully functioning communicative system with all characteristics of a typical human language even though Cena developed in a linguistic vacuum. What makes Cena interesting is that we are reasonably certain that Cena had no external input from the national sign language, Libras, or any other language during its formation. Cena challenges the assumption that to acquire the first language, the child must be exposed to a fully developed language. It developed from homesigns to an emergent sign language that is used for all aspects of village life. Cena also lends credence to the interactional model of language acquisition, which considers the interactions between the child and the caregivers to be the crucial element. The nativist model of language acquisition, which assumes a universal system underlying language, also plays a part. Through interaction, what arose is a system with characteristics essential to all human language.