Relative salience of acoustic features in zebra finch song.

Abstract

Zebra finch song consists of complex acoustic elements repeated over several hundred milliseconds with extreme vocal-motor precision. Much less is known about how song is perceived though previous work has shown that zebra finches easily discriminate between normal and time-reversed versions of song syllables. Here, we used operant conditioning, psychophysical methods, and various synthetic song models to assess the bird’s sensitivity to local versus global temporal changes in song and to determine which cues are most salient in these complex syllables. Birds could discriminate syllable reversals in songs made up of the song envelope filled with noise, suggesting that syllable envelope cues can provide the basis for discrimination. However, birds could also discriminate syllable reversals in songs made up entirely of Schroeder harmonic complexes, stimuli that provide only phase (reversals of fine structure) cues without syllable envelope cues. Birds performed better on longer syllables, suggesting a window of temporal integration for fine structure discrimination. In contrast, humans could perceive few of the syllable reversals within these song modifications. This fine-grained perception in birds suggests that the machinery used for song perception is as precise as the machinery used for song production. [Work supported by NIH.]