Although parrots have long been known for their ability to mimic human speech, animal psychologist Irene Pepperberg set out to show that their vocal behavior could have the characteristics of human language. She worked intensively with a single African Grey Parrot, Alex, and reported that he acquired a large vocabulary and used it in a sophisticated way, often compared to that of a two year-old child. Alex died in September 2007 at age 31. Pepperberg runs The Alex Foundation, devoted to research in bird communication.