Nicaraguan Sign Language (also known by its Spanish name, "Idioma de Signos Nicaraguense"), developed in the early 1980s and with a native "speaker" base in the low four figures, is the world's youngest known fully-featured language, and the closest thing humanity has to a documented spontaneous generation of language. As such, it is a subject of significant importance to linguists, developmental psychologists, and cognitive scientists, and it ranks up there with the "Genie" case as one of the most productive views into language learning and development, and bases for the advancement of one or another theory, that researchers have access to. That is, at least as long as the ideal experiment, as conceived of since at least as early as ancient Greek antiquity, that of raising humans from birth in complete linguistic isolation, is generally considered unethical, and more importantly from an academic point of view, difficult to get funding for.

Historically, deafness is a strongly stigmatized condition in the Nicaraguan region, and this prejudice, combined with the generally rural and undeveloped nature of the country, conspired to generally keep individual deaf children close to their homes for the majority of their lives. Of course, if the deaf were kept close to home and tended not to socialize much, let alone interact with other deaf people, it was very unlikely that they would give birth to deaf offspring – the genetic deafness rate was particularly low in Nicaragua, and a given genetically deaf child was usually the offspring of two hearing carriers of recessive genes. Of course, nutritional issues, sickness, and a general lack of non-ototoxic (damaging to the structures or nerves of the ear) medicines, or often any medicines at all, lead to moderate incidence of nongenetic deafness, especially among children, but I digress – the point is, in either family or outside society, the deaf would rarely interact with any non-hearing individuals, and few of those knew anything of any deaf language, many having little knowledge of the written form of the language (typically Spanish) which they did understand.

Absent parents prepared to teach them, a deaf (sub)culture to learn from, or even written language to observe, deaf Nicaraguans thus rarely learned any language, communicating with their family with a small vocabulary of simple, representative improvised gestures known as "home signs" or "mimicas" which generally operated on a sophistication level equal to or below telegraphic speech. Each individual's signing lexicon was particular to their family, and rarely showed any signs of stable grammar or syntax. (However, it is worth noting that in such cases, the deaf child does employ more regularity and structure in use of signs than the parents or other family.)

In any case, after who knows how long of this status quo, the FSLN ("Sandinistas") came to power in Nicaragua in 1979. As part of their course of consolidating power and taking on the functions of a ruling government, they embarked on a nationwide literacy and education campaign, one of the elements of which was the gathering of deaf children from throughout the country and their placement in two schools in Managua - San Judas, a primary school, and Villa Libertad, the allied vocational school. The question then became one of how to teach these people, who knew no language, to communicate. The answer, as supported by educational advisors from the Soviet Union, was finger spelling. This was the wrong answer. Teaching people to spell with their hands is of significantly reduced value when they have, for the most part, no exposure to the concept of letters, or words, let alone word order, or inflection, or syntax, or case and tense, or arguably the very concept of human language itself, as an abstracted representation of ideas and information.

So for the most part, the teachers and children found themselves incapable of communicating with each other. Likewise, the children had no way to talk amongst themselves. At first. As time went on, and the children used their own home signs among themselves, some of these signs came to be adopted as universal – the children had a pidgin and this came to be their lingua franca. As a pidgin, it was very basic, with limited vocabulary and structure, useful mostly as a way to communicate information where nothing else would do. However, by at least 1986, when the linguist Judy Kegl visited the schools and performed the first official studies of the children's language, some of the children had developed the pidgin into a full-fledged language, with universal and extendible grammatical structure, a broader vocabulary, higher-level abstraction in symbols, and such nuances as verb agreement. Very interesting is the matter of where this language developed - the majority of the Villa Libertad students still operated with the rudimentary version of the language, whereas it was the San Judas children in whom the fully featured strain was witnessed, and who exhibited fluency and regularity in their "speech". This pattern fell entirely in line with contemporary theories hypothesizing a "language learning instinct" present in the first decade or so of life, through which some unknown mechanism or function of the brain makes it easier and far quicker to internalize and understand languages in early youth (when a person's first language is learned) than in adolescence or later (when, for most non-native bilinguals, further languages are learned).

More important than in whom Nicaraguan Sign Language developed, however, is the fact that it developed at all. How does a language form out of nothing? Supporters of Chomsky's Universal Grammar and similar theories would suggest that language, not any particular language, but the concept of linguistic structure, transformations, and meaning, is resultant of structures native to the brain from birth, that humans are inherently wired to communicate. Given a medium, as most people are in the home, it will be internalized and adopted. Lacking one, as with the deaf of Nicaragua, the mappings of language to structure will be created from scratch. The experience of Nicaraguan children can be seen as a significant validation of these theories.

Some linguists, on the contrary, argue that NSL was not truly created from scratch, and cannot be taken as evidence of a drive to make language from nothingness. The children had had some exposure to language, their families' knowledge of native languages at least informing the manner in which they communicated through signs, and the NSL lexicon indicating at least some exposure to American Sign Language. Further, there is the issue of those children who might have been raised in literate families, or those not deaf from birth, who brought in whatever knowledge of language they had accumulated during their earlier years. Against these arguments, critics play up the dissimilarity between NSL and Spanish, pointing out unique structures such as the construction of prepositions as similar to verbs - that is to say, where a language like English would form "Mary is on the bed" (and Spanish would give "Maria esta en la cama"), NSL, literally translated, would form something like "Mary ons the bed", without a copula. Even if NSL did not represent true spontaneous generation of language, its is still linguistically significant, as the formation of a creole without a clear substrate or lexifier.

Nicaraguan Sign Language is still in use - the vocabulary continues to grow, a written form has been created by importing the Danish "SignWriting" alphabet, and original graduates of the Managua schools have paired off and given birth to deaf children who learn it in the home. NSL education is to a significant extent subsidized by linguists and researchers, founding new schools in remote areas of the country and forbidding the employment of other sign languages in an attempt to maintain the purity of the original, and this does create some controversy - NSL is a highly captive language, with what is in the broad view a ridiculously low number of speakers, and some argue that in attempting to observe the language in isolation, researchers are in effect leaving the deaf of Nicaragua not that much more prepared to make a living or deal with the broader society than they were before the educational reforms of the Sandinistas. All in all, an interesting sideshow to the "Deaf Culture" skirmishes in areas of the established languages, and in the broad view, just about as irrelevant to the general public.