Without criteria for what counts as a U/N-shaped developmental trajectory, it is not clear how many legitimate "Us" really exist. Many, if not all, "Us" may turn out to be illusions borne out of our sampling methods, task construal, and blurry lenses of description. (Contains 2 figures.)

Language training for the non-verbal or language delayed child should utilize feedback to reinforce correct responses and should closely follow the syntactical development of normal children. The two basic areas of language training are receptive and expressive. Receptive language training includes attending and responding, following single phase…