Abstract:

The tonal quality and temporal complexity of bird vocalizations have long suggested that birds may excel in auditory spectral or temporal processing. However, most psychophysical studies support the notion that birds have spectral and temporal resolving power roughly comparable to that measured in humans. Rarely have such psychophysical tasks involved both frequency and time cues. An intriguing aspect of gap-detection experiments with sinusoidal markers is the robust dependence on the frequency separation between the markers. In humans, silent gaps become more difficult to discriminate as the frequency difference between the markers increases. This frequency-dependent pattern of thresholds is well fit with a roex-filter model. Here, budgerigars were trained by operant conditioning to discriminate a change in the duration of a silent gap between two tonal markers. Frequency separation between the tonal markers had only a small effect on gap discrimination thresholds in budgerigars, suggesting an unusually broad peripheral auditory filter. This result stands in marked contrast to the results from humans and to estimates of the auditory filter in budgerigars using masking paradigms. Alternate explanations for the apparently broad tuning of the discrimination data will be considered. [Work supported by NIH grants DC-00198 and MH-00982 to RJD.]