A remarkable case of avian vocal learning concerned a talking African grey parrot called Alex.
What could Alex do?
To quote from Dr. Pepperberg's account, Alex was “able to participate in some forms of inter-species communication”. Alex was capable of demonstrating more than simply the ability to imitate human speech patterns.
Alex was trained to identify vocally certain objects, like “key” and “paper”, by name. It was also taught to name certain colours such as “green” and “blue”, and certain shapes with labels like “three corner” (easier to learn than triangle) in order to categorise objects with respect to colour and shape. It also learnt to recognise quantities of objects up to five and learnt the functional use of the word “no” as well as phrases such as “come here” and “wanna go”. After five years it had been taught a functional repertoire of about 40 vocalisations.
When an object was held up before the bird, it identified the object accurately eight times out of ten. His most frequent errors was either the omission of the colour or shape adjectives, or the unclear pronunciation of the colour adjectives. For example, when the trainer held up a green key and said “What's this?" Alex answered “green key” only 69% of the times. If the answer that he gave was simply “key” as it often was, the trainer then put the question “what colour key?". The bird usually got it right second try and raised its score from 69% to 94%. When randomly shown unfamiliar objects of familiar colours, the bird could not, of course, identify the objects, but invariably got the colour right.
The vocabulary of Alex
Whenever he incorrectly identified an object, Alex was told “no”. After about 18 months of training, he began to use the word to his trainer when he appeared to wish not to be handled. Trainers then started to use the word “no” when refusing to relinquish an item desired by the parrot. Soon Alex would use the word “no”. When refusing to identify a proffered object, he would say “no”. “No” was also employed to reject unacceptably small pieces of food, and to reject toys apparently too worn to be of interest. In many cases the refusals to identify or relinquish are accompanied by the turning of his head away from the trainer.
Besides using words in the use of which he was trained, Alex spontaneously but meaningfully used other words that he had picked up. For example, although he had not been trained to produce labels for the various foods, he “requested” food items or objects by speaking their names, prefaced by “want”. If a trainer took a particularly popular object, a cork, from a drawer and Alex saw it, he would say “want cork”. He also asked for objects not in view. And if a wrong object was proffered, he either said “no” and refused to take it, or he briefly accepted and then threw it back! He called for particular “foods” or “water”, even for “nut” or “corn”.
Alex and language
Perhaps the most telling achievement of all was Alex's ability, although limited, to innovate simple combinations of words. For example, having previously been trained to identify certain objects as “green” and a clothes peg as the object “peg wood” (but never as a green one) the bird was offered a green clothes peg. He said “green wood, peg wood”. He should have said “green peg wood” but he was linking phrases already in his vocabulary. Later he identified on first-ever presentation “blue peg wood”, “green cork” and “blue hide”.
To segment phrases and recombine the elements in this way is to begin to meet one crucial criterion in the definition of true language.