Delayed matching-to-sample by an echo-locating bottlenose dolphin

Abstract

An Atlantic bottlenose dolphin (Tursiops truncatus) was trained to perform three-alternative delayed matching-to-sample while wearing eye cups to occlude its vision. Samples and comparison stimuli consisted of small aspect-independent three-dimensional stimuli. Observing responses, in the form of echo-location clicks, were recorded during the presentation of the sample as well as during the presentation of the comparison stimuli. The location, duration, and rate of clicks to the sample and to each comparison stimulus was recorded. Over 48 sessions of testing, choice accuracy averaged 94.4% correct. Stimuli varied in the number of clicks necessary to identify it as the sample. Examination of the number of echolocating signals emitted and their distribution over locations reveals a complex decision making process in which stereotyped sequences are combined with contingent item identification to yield accurate performance. A model for the dolphin's decision-making processes is described.