The Last Polyglot.

Alex, an African grey parrot, could name fifty objects, count to six, and say "I'm sorry." For thirty years, scientist Irene Pepperberg asked whether he truly knew a word or only performed one — and the answer changed how we see every animal that has ever tried to speak to us. The Last Polyglot is the true story of that question, told as a murder-mystery documentary: who killed the idea of an animal mind, and can we ever prove what was inside the bird?