Build-up effect of auditory streaming in budgerigars (Melopsittacus undulatus)

Abstract

When listening to a rapid tone sequence of the form ABA-ABA-ABA-… (where A and B are two tones of different frequencies and “-” indicates a silence interval), listeners may either hear one coherent “gallop” of three tones grouped together or two separate auditory streams (one high frequency, one low frequency) appearing to come from two sound sources. Research on humans indicates that the tendency to perceive two streams can be built up as exposure time increases. Neural recordings in European starlings show build-up effects of auditory streaming too. A lack of behavioral data on the build-up effect in nonhumans make it difficult to draw parallels between animals and humans. The present research aims to behaviorally validate the build-up effect of auditory streaming and factors that may influence the effect in nonhuman animals. Four budgerigars were tested in a categorization task using operant conditioning. “Streaming” categorization increased as the frequency separation increased. Additionally, in some frequency separations, as the sequence duration increases, the probability of “streaming” categorizations reported by the budgerigars is higher. These results indicate that budgerigars experience a build-up effect of auditory streaming behaviorally, and this effect is influenced by, but may not be limited to, different frequency separations.