Spectral cues and temporal integration during cylinder echo discrimination by bottlenose dolphins (Tursiops truncatus)

Three bottlenose dolphins (Tursiops truncatus) participated in simulated cylinder wall thickness discrimination tasks utilizing electronic phantom echoes. The first experiment resulted in psychometric functions (percent correct vs wall thickness difference) similar to those produced by a dolphin performing the task with physical cylinders. In the second experiment, a wide range of cylinder echoes was simulated, with the time separation between echo highlights covering a range from 300 mu s. Dolphin performance and a model of the dolphin auditory periphery suggest that the dolphins used high-frequency, spectral-profiles of the echoes for discrimination and that the utility of spectral cues degraded when the time separation between echo highlights approached and exceeded the dolphin's temporal integration time of similar to 264 mu s.