There seem to be counterexamples. https://en.wikipedia.org/wiki/Feral_child#Raised_in_confinement https://en.wikipedia.org/wiki/Feral_child#Raised_in_confinem..

There seem to be counterexamples. https://en.wikipedia.org/wiki/Feral_child#Raised_in_confinement https://en.wikipedia.org/wiki/Feral_child#Raised_in_confinem... "Isabelle (1938) was almost seven years old when she was discovered. She had spent the first years of her life isolated in a dark room with her deaf-mute mother as her only contact. Only seven months later, she had learned a vocabulary of around 1,500 to 2,000 words. She is reported to have acquired normal linguistic abilities."