The Dolphin Institute - Dolphin Research Summaries

(C) 1969 University of Hawaii

The performance of two female Atlantic bottlenosed dolphins Tursiops truncatus (Montagu) on complex learning tasks was investigated using discrimination learning set (DLS) and successive reversal training (SRT) as the experimental tasks. There have been few previous attempts to assess the ability of these animals in performance on standardized learning tasks.
Although the procedures and stimuli employed in reported research on SRT have varied, DLS experiments have usually presented visual stimuli in some modified form of the Wisconsin General Testing apparatus. In the present study, however, there was an attempt to optimize the experimental situation for the dolphins by requiring them to discriminate between auditory stimuli, thereby employing a sensory modality probably superior to the visual one for this animal.
The test stimuli used for DLS were 180 pairs of electronically produced complex sound patterns. The paired patterns to be discriminated were presented simultaneously, one pattern at each of two underwater speakers separated by 25 feet. The dolphin responded by swimming through a central channel, approaching one of the two speakers to within approximately 3-6 inches, and “pointing” at the speaker with her rostrum. A response to the arbitrarily designated “correct” pattern was rewarded by onset of a conditioned reinforcement tone, followed by food reward. The stimulus pairs were presented in a continuous cycle of two seconds on, and one second off, by means of a recorded tape loop. For SRT a single pair of complex sound patterns were employed with their values being reversed each time the dolphin reached either of the dual criteria of seven consecutive correct responses or nine correct in a series of ten responses.
In order to provide information regarding the transfer effects from one experimental task to the other, one animal was tested initially on 180 DLS problems prior to 1500 trials of SRT. The other animal was presented with the DLS problems subsequent to SRT.
Preliminary testing showed the animals fully capable of localizing the source of a single stimulus emitted from one of the two underwater speakers. Additional preliminary testing established a high degree of discriminability (89-100%) between several pairs of simultaneously presented sound patterns.
SRT results showed progressive improvement over reversals for both animals with one S reaching an asymptotic level comparable with performance demonstrated by primates tested with visual stimuli.
Over the course of the 180 DLS problems administered, neither dolphin convincingly demonstrated formation of a discrimination learning set, although both Ss provided some evidence of improvement within these problems.

Beach, F. A. III (1969). Complex learning in the dolphin with auditory stimuli. Unpublished doctoral dissertation, University of Hawaii, Honolulu.

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