Effects of echo phase on bottlenose dolphin jittered-echo detection

The ability of bottlenose dolphins to detect changes in echo phase was investigated using a jittered-echo paradigm. The dolphins' task was to produce a conditioned vocalization when phantom echoes with fixed echo delay and phase changed to those with delay and/or phase alternated (jittered) on successive presentations. Conditions included: jittered delay plus constant phase shifts, +/- 45 degrees and 0 degrees-180 degrees jittered phase shifts, alternating delay and phase shifts, and random echo-to-echo phase shifts. Results showed clear sensitivity to echo fine structure, revealed as discrimination performance reductions when jittering echo fine structures were similar, but envelopes were different, high performance with identical envelopes but different fine structure, and combinations of echo delay and phase jitter where their effects cancelled. Disruption of consistent echo fine structure via random phase shifts dramatically increased jitter detection thresholds. Sensitivity to echo fine structure in the present study was similar to the cross correlation function between jittering echoes and is consistent with the performance of a hypothetical coherent receiver; however, a coherent receiver is not necessary to obtain the present results, only that the auditory system is sensitive to echo fine structure. https://doi.org/10.1121/10.0019717

Automated summary

The study investigated the ability of bottlenose dolphins to detect changes in echo phase using a jittered-echo paradigm. The dolphins were able to discriminate between different echo fine structures, showing sensitivity to changes in phase and delay. The results suggest that the auditory system of dolphins is sensitive to echo fine structure, similar to a coherent receiver.