Nicaraguan Sign Language is a documented case of a language emerging from zero language exposure, not merely zero standard-language exposure

Most deaf children acquire language under impoverished but non-zero conditions: roughly 90% are born to hearing parents and so lack sign-language input at home, yet many live near sign-using communities that supply a model. Susan Goldin-Meadow, commenting on Ann Senghas's cohort studies in Human Development (53(5), 2011), draws a sharper line for the Nicaraguan case: "the deaf individuals studied by Senghas find themselves in an even more extreme situation – there is no sign language in the community to be exposed to. What Senghas shows us is that, under these circumstances, a language can develop."

The distinction is what makes Nicaraguan Sign Language (NSL) unusual even among deaf-language-acquisition cases. It is not a study of children acquiring a degraded or partial version of an existing language; it is a study of a language system arising where no language model existed to be transmitted. The deaf children brought only individually invented home-sign gestures, and out of their contact with one another a shared, conventionalized system emerged. NSL is therefore frequently described as the clearest natural experiment linguistics has on the birth of a language from a starting point of no linguistic input.

The specific mechanism by which that system then complexified — a generational handoff in which later child learners regularized the grammar further than its adult originators — is a distinct claim, treated in claim-nsl-second-cohort-child-learners-systematized-grammar-beyond-founders. The social and educational setting in which the population was first assembled is treated in claim-nsl-emerged-in-managua-schools-after-failed-oral-spanish-curriculum. As a case of linguistic structure emerging through repeated transmission across learners, NSL is the empirical counterpart to the transmission-chain framing in claim-iterated-learning-theory-reframes-model-collapse-as-cultural-evolution.