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