Relier Pairs Critical PeriodVersion en ligne Critical Period par Jenny Sanjuanita 1 Universal Grammar 2 Noam Chosmky 3 Genie (1970) 4 The czech twins (1972) 5 Isabelle (1930) 1965. Proposed Language Acquisition Device (LAD) Languages need to have generalizable grammatical rules Her deaf-mute mother as her only contact. She had no sense of language. Her case served to study wheter language could be taught even after critical periods for language development had been missed. They had been kept locked in insolation in a cellar with only each other for company. They little speech and communicated mostly in gestures.