The Dolphin Institute - Dolphin Research Summaries

(C) 1994 University of Hawaii

A female bottlenosed dolphin (Tursiops Truncatus) was shown capable of immediate cross-modal recognition using echolocation and vision with complexly shaped objects. The dolphin immediately recognized objects visually which had been experienced earlier echoically which had been experienced earlier visually. Successful recognition was not predicated on the dolphin experiencing objects simultaneously using vision and echolocation. To examine cross-modal recognition an “echoic” box was fabricated. Objects suspended underwater inside the box were available for echoic inspection but not for visual inspection. Conversely, objects held in air were available for visual inspection by the dolphin but not for echoic inspection A Matching-To-Sample (MTS) task was employed to examine cross-modal recognition and also to examine within-modal recognition. To test echoic-visual (E-V) recognition a single echoic box was used. The dolphin inspected two alternative objects held in air. A correct response required the dolphin to station in front of the alternative matching sample. To test visual-echoic (V-E) recognition, two echoic boxes were used. The dolphin first inspected a sample object held in air. Then two alternative objects were suspended in boxes. For a correct response the dolphin pressed a paddle attached to the box containing the alternative matching the sample. Following preliminary training, cross-modal recognition was tested with eight pairs of novel objects which had been pre-calibrated separately in pure echoic matching and pure visual matching. Cross-modal performance across all pairs was 94.3% and 97.1% in E-V and V-E MTS, respectively. The dolphin demonstrated both immediate E-V and V-E recognition by matching at significantly above chance levels on the first occurrence of each object acting as sample. Further tests revealed the dolphin’s ability to immediately perform V-E MTS with sample objects displayed on a small television monitor placed in an underwater window. The results of both studies demonstrate a profound ability by the dolphin for immediately recognizing complexly-shaped objects across the senses of vision and echolocation. The findings strongly suggest that the sense of vision and echolocation in the dolphin are integrated and coordinate at the representative level.

Pack, A. A. (1994). Cross-modal Recognition of Complexly-Shaped Objects by a Bottlenosed Dolphin (Tursiops truncatus) using Vision and Echolocation. Unpublished Dissertation, University of Hawaii, Honolulu.

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