The proof that these birds can reason and use English is inherent in one remarkable incident. Many times over the course of 30+ years, Alex decided not to answer questions or asked to go back to his cage instead. One day was different. Alex was answering questions about objects in front of him and the answers required more than simple memorization of words spewed out at random. When he reached the last question, he gave every answer possible, except the correct answer.
Dr. Pepperberg gave him a time out in his cage and left him all alone. In about 30 minutes, the doctor returned and released the now seemingly contrite bird, who instantly piped up “Sorry!” followed by the correct answer to the last question asked some little time ago. The length of memory of that question beats some human performance on memory portions of IQ tests, such as the Wechsler edition administered to adults. That bird was playing a joke during testing or had been fed up with answering and become a wiseguy. How human, we’d say.