Linguistics
A chimp learned 125 signs - but never actually learned grammar
In the 1970s Herbert Terrace raised a chimpanzee named Nim Chimpsky (a jab at Noam Chomsky) and taught him American Sign Language. He first believed Nim was stringing signs into real sentences, but frame-by-frame video review showed Nim mostly imitated or interrupted his trainers rather than initiating language, and his utterances didn't grow more complex with age the way a child's do. Terrace's reversal became a landmark argument that apes can learn symbols but not syntax.