“Alex had a vocabulary of over 100 words, but was exceptional in that he appeared to have understanding of what he said. For example, when Alex was shown an object and was asked about its shape, color, or material, he could label it correctly. He could describe a key as a key no matter what its size or color, and could determine how the key was different from others. Looking at a mirror, he said “what color”, and learned “grey” after being told “grey” six times. This made him the first and only non-human animal to have ever asked a question—and an existential question at that. (Apes who have been trained to use sign-language have so far failed to ever ask a single question.) Alex’s ability to ask questions (and to answer to Pepperberg’s questions with his own questions) is documented in numerous articles and interviews.
Alex was said to have understood the turn-taking of communication and sometimes the syntax used in language. He called an apple a “banerry” (pronounced as rhyming with some pronunciations of “canary”), which a linguist friend of Pepperberg’s thought to be a combination of “banana” and “cherry”, two fruits he was more familiar with.
Alex could add, to a limited extent, correctly giving the number of similar objects on a tray. Pepperberg said that if he could not count, the data could be interpreted as his being able to estimate quickly and accurately the number of something, better than humans can. When he was tired of being tested, he would say “Wanna go back”, meaning he wanted to go back to his cage, and in general, he would request where he wanted to be taken by saying “Wanna go…”, protest if he was taken to a different place, and sit quietly when taken to his preferred spot. He was not trained to say where he wanted to go, but picked it up from being asked where he would like to be taken.
If the researcher displayed irritation, Alex tried to defuse it with the phrase, “I’m sorry.” If he said “Wanna banana”, but was offered a nut instead, he stared in silence, asked for the banana again, or took the nut and threw it at the researcher or otherwise displayed annoyance, before requesting the item again. When asked questions in the context of research testing, he gave the correct answer approximately 80 percent of the time.”