<P> The species is common in captivity and is regularly kept by humans as a companion parrot, prized for its ability to mimic human speech, which makes it one of the most popular avian pets . An escaped pet in Japan was returned to his owner after repeating the owner's name and address . </P> <P> They are notorious for mimicking noises around their environment and using them tirelessly . While they are highly intelligent birds, they need enrichment and attention in captivity or they can become distressed; feather plucking is a common symptom . However, they may be prone to behavioural problems due to their sensitive nature . </P> <P> Grey parrots are also highly intelligent, having been shown to perform at the cognitive level of a 4--to 6 - year - old child in some tasks . New experiments have shown that grey parrots can learn number sequences and can associate human voices with those humans' faces . Most notably, Dr Irene Pepperberg's work with Alex the parrot showed his ability to learn over 100 words, differentiating between objects, colours, materials, and shapes . </P> <P> Grey mutations occur naturally in the wild, like the Blue Ino (albino), Incomplete Ino, and Blue varietals . The Blue Ino is all white . The Incomplete Ino has light pigmentation . The Blue has a white tail . </P>

How many words can a grey parrot learn