The 'idioglossia' cases of the 1890s and the clinical investigation and treatment of developmental language impairment.

The early history of developmental language impairment in late 19th century Britain is considered through the critical examination of three papers appearing in 1891 by Hadden, Golding-Bird and Hale White, and Taylor. They represent innovative investigations of child language disorders whose themes and concerns are resonant today. The term 'idioglossia' was coined to identify this new impairment and reflected the belief by some that these children spoke an invented language. Rather than viewing these children as having some constitutional deficiency, these 19th century physicians were novel in insisting that children with language impairments merited extensive clinical investigation and treatment. Their case descriptions and the subsequent debates regarding classification and prognosis are reviewed. Further consideration is given to how these cases led to questioning the relation between language and speech and other aspects of child development and disorder. Reflection on the early sources of clinical categories provides a new perspective on our current formulations for variation in developmental language trajectories.