  However, there is a case of creolization in which these other  hypotheses apparently fail to gain purchase, as Pinker (1994:37ff.)  emphasizes. This is the case of the development of Idioma de Signos  Nicaragüense (ISN, Nicaraguan Sign Language), a brand-new  natural sign language which first emerged around 30 years ago in  schools for the deaf in and around Managua. These schools were first  set up in the 1970s, and ISN evolved from the hodge-podge of homesign systems used by students who entered the schools at that time. ISN is an interesting test case of the bioprogram hypothesis for two  reasons. First, homesign systems are idiosyncratic and possess little syntactic structure: the natural-languagelike syntax of ISN could  therefore not derive from substrate influence. And Spanish, the only  potential candidate for superstrate influence was allegedly  inaccessible to signers because of its auditory modality. Pinker  claims that ISN provides another example of creolization and the  workings of the innate language faculty: it is  “created…in one leap when the younger children were  exposed to the pidgin singing of the older children.”  (1994:36-7)