The auditory time resolution in bottlenose dolphins: Behavioral experiments versus auditory evoked potential methods

Abstract

Non‐invasive auditory evoked potentials (AEP) methods are now widely used to study dolphins' hearing because some auditory characteristics can be obtained much faster compare to behavioral methods. The bottlenose dolphin auditory time resolution assessed using evoked potentials responses to a double click, amplitude modulated tone and periodic click is generally believed to be around 300 microseconds. This assessment is claimed to be in full agreement with behavioral measurements. The intention of this paper is to reevaluate behavioral results which are believed to support AEP methods in light of numerous behavioral results indicative of the bottlenose dolphin time resolution as high as 20‐30 microseconds. We found that as long as there are differences in waveforms, bottlenose dolphins are able to discriminate between very short (as short as a bottlenose dolphin sonar click) signals with identical energy spectra as well as between brief noise signals with random energy spectra. Auditory evoked responses do not reveal any differences between such signals whereas the differences are readily indicated by behavioral responses of the dolphins. The auditory temporal analysis of brief signals in bottlenose dolphins seems to be inaccessible by AEP methods, at least in their present form.