Use of transition and abstract rules by budgerigars in auditory pattern processing

Abstract

Budgerigars, a small species of parrot, are open-ended vocal learners that produce a long, rambling warble song. Past work has shown that these birds are sensitive to changes in the order of their song elements but it is not clear what rules they may use to process changes in sounds sequences. Here, we used operant conditioning and psychophysical techniques to ask how budgerigars discriminate among patterned auditory sequences. In these experiments, auditory sequences of the form AAB, composed of pure tones or natural warble elements, were played to the bird as a repeating background until the bird pecked a key to initiate a trial. During a trial, either a target sequence played that differed from the background in the order of the elements or a sham trial occurred where there was no change. Results show that budgerigars use rules about the transitions between elements to detect targets. Further experiments using multiple background sequences show that the birds are also sensitive to the underlying abstract pattern of sounds (same-same-different). Thus, with their ability to attend to surface transition rules (phonology-like) and deeper abstract patterns (syntax-like), budgerigars are a useful vocal learning model for studying the neurobiology and evolution of language.