The development of language-like  communication without a language model.
Deaf children who are unable to acquire oral language naturally and who are not exposed to a standard manual language can spontaneously develop a structured sign system that has many of the properties of natural spoken language. This communication system appears to be largely the invention of the child himself rather than of the caretakers.
D002675:Child, Preschool; D003638:Deafness; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008369:Manual Communication; D012660:Semantics; D012813:Sign Language