Recognition and Discrimination of Human Actions Across the Senses of Echolocation and Vision in the Bottlenose Dolphin: Evidence for Dolphin Cross-modal Integration of Dynamic Information

Abstract

The ability of cetaceans to explore and interpret their world via echolocation has received considerable attention during recent years, and the resulting body of work has revealed a sophisticated cetacean echolocation system. In addition, a number of recent studies suggest that dolphins can relate information that they receive from vision with information that they obtain from echolocation when this information concerns stationary objects. However, the present study is the first test of the cetacean ability to integrate dynamic information about movement across the two senses. Three adult female bottlenose dolphins that had previously learned to interpret visible movements produced by humans stationed on floating docks were asked to interpret a set of these movements produced by an underwater human located behind a visually opaque screen. Although each dolphin had previously demonstrated its ability to reliably interpret movements produced by a human in the air above the surface of the water, none of the dolphins had any previous experience with underwater humans producing movements that the dolphins could see or with underwater humans producing movements behind an opaque screen that prevented the dolphins from using visual information to interpret these signals. The dolphins quickly learned to correctly respond to signals that they could not see but could observe via echolocation. These results demonstrate that dolphins can relate visual and echoic representations of actions, although the amount of experience necessary for such integration has yet to be determined.