For many passerines, the extent,timing, and even presence of allospecific vocal learning can be influenced by the form of input that is received. Little data exist, however, on vocal learning in parrots (Psittacidae). I have previously proposed that such vocal learning proceeds most readily when input is (1) referential, (2) contextually applicable, and (3) interactive. The referential aspect demonstrates the meaning of the code to be taught, the contextual aspect demonstrates the use that can be made of the information contained in the code, and the interactive aspect provides explicit training that is constantly adjusted to the level of the learner. To obtain information on the relative importance of these three aspects of input on learning in a mimetic species, I used three different conditions to train two juvenile Grey Parrots (Psittacus erithacus) to produce English labels to identify various common objects. Each bird experienced: (1) audiotaped tutoring, which was nonreferential, noninteractive, and did not demonstrate contextual applicability; (2) videotapes, which provided reference and limited information about context, but which were noninteractive; and (3) live human tutors, who interactively modeled the meaning and use of the labels to be learned. The birds learned only from the live tutors. A third parrot, trained on a separate set of labels by tutors who provided only limited reference and context for those vocalizations, learned to produce that set of labels without comprehension. The data suggest that, even for birds known for their mimetic abilities, social interaction, reference, and full contextual experience are important factors in learning to produce and comprehend an allospecific code.
Pepperberg, I. M. (1994). Vocal learning in grey parrots (Psittacus erithacus): effects of social interaction, reference, and context. The Auk, 300-313.