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. Once, Alex was given several different colored blocks (two red, three blue, and four green—similar to the picture above). Pepperberg asked him, "What color three?" expecting him to say blue. However, as Alex had been asked this question before, he seemed to have become bored. He answered "five!" This kept occurring until Pepperberg said "Fine, what color five?" Alex replied "none". This was said to suggest that parrots, like humans, get bored. Sometimes, Alex answered the questions incorrectly, despite knowing the correct answer. Preliminary research also seems to indicate that Alex could carry over the concept of four blue balls of wool on a tray to four notes from a piano. Pepperberg was also training him to recognize the symbol "4" as "four". Alex also showed some comprehension of personal pronouns; he used different language when referring to himself or others, indicating a concept of "I" and "you". In July 2005, Pepperberg reported that Alex understood the concept of zero. If asked the difference between two objects, he also answered that; but if there was no difference between the objects, he said "none", which meant that he understood the concept of nothing or zero. In July 2006, Pepperberg discovered that Alex's perception of optical illusions was similar to human perception. Pepperberg was training Alex to recognize English graphemes, in the hope that he would conceptually relate an English written word with the spoken word. He could identify sounds made by two-letter combinations such as SH and OR. Death Alex's death on 6 September 2007, at age 31, came as a surprise, as the average life span for a grey parrot in captivity is 45 years.