Isabelle (1932-?) is the name (pseduonym?) of an American feral child who was discovered in 1938, aged 6 years old. She had been living in a darkened room with her deaf-mute mother and had had no exposure to language. After intense training, by age 9 she was in the normal range. It is generally considered that she had not yet passed the critical period for language acquisition, and was therefore able to acquire language nearly naturally.