fellow parrot in the lab. Alex sometimes practiced words when he was alone. Accomplishments Pepperberg did not claim that Alex could use "language", instead saying that he used a two-way communications code. Listing Alex's accomplishments in 1999, Pepperberg said he could identify 50 different objects and recognize quantities up to six; that he could distinguish seven colors and five shapes, and understand the concepts of "bigger", "smaller", "same", and "different", and that he was learning "over" and "under". Alex passed increasingly difficult tests measuring whether humans have achieved Piaget's Substage 6 object permanence. Alex showed surprise and anger when confronted with a nonexistent object or one different from what he had been led to believe was hidden during the tests. 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 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 the word "grey" after being told "grey" six times. This made him the first and only non-human animal to have ever asked a question, let alone an existential one (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, as well as 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