Before the 1970s, deaf people in Nicaragua were largely isolated, communicating with hearing family members through improvised home signs that had no grammar and no consistency from one household to the next. When a special education center opened in Managua in 1977, followed by a vocational school in 1980, hundreds of deaf children were brought together for the first time. The official plan to teach them spoken Spanish and lip-reading failed, but on the playground and the school buses the children began merging their home signs into something new.

This episode follows how that first-stage system, LSN, was transformed by younger students into the grammatically complex ISN, and how MIT linguist Judy Kegl arrived in 1986 to document it. We explore the mechanics the children built, from the ABA pattern for describing motion to spatial modulati ...