  In support of the critical period hypothesis about language,  Lenneberg cited the facts (i) that retarded (e.g., Downs syndrome)  children's language development stops around puberty; (ii) that  whereas very young children are able to (re)learn language after  aphasias produced by massive left-hemisphere trauma (including  hemispherectomy), aphasias in older children and adults are typically not reversible; and (iii) that so-called ‘wild children,’ viz., those who grow up with no or little exposure to human language, exhibit severely compromised language skills. (Lenneberg,  1957:142-55; see Curtiss 1977 for the (in)famous case of Genie, a  modern-day ‘wild child’ from suburban Los Angeles, who  was unable to acquire any but the most rudimentary grammatical  competence after a miserable and wordless childhood spent locked  alone in a room, tied to her potty chair or bed.)