International Journal of Comparative Psychology

Studies of sensory, cognitive, and communicative skills of bottlenose dolphins ( Tursiops truncatus ) were carried out over a 34-year period at the Kewalo Basin Marine Mammal Laboratory in Honolulu. Findings on sensory skills included fine discrimination of auditory frequency differences andauditory duration, good visual resolution capabilities in water and in air, and sharing of object recognition across the senses of vision and echolocation. Short-term memory for auditory and visual materials was well developed, including memory for lists of items. Concept learning was demonstrated within several paradigms, including discrimination learning sets and matching-to sample. Dolphins understood novel instructions conveyed within artificial gestural or acoustic language systems using “sentences” as long as five words whose interpretation required processing of both the semantic and syntactic features of the languages. Gestural instructions were understood as reliably when conveyed through television images of trainers as when conveyed by live trainers. The words of these languages were understood referentially, including an ability to report whether a referenced object was present or absent in the dolphin’s tank. Both vocal mimicry of novel sounds and behavioral (motor) mimicry of other dolphins and of humans was demonstrated, an extensive and unique dual ability among animals tested, including an understanding of the concept of imitate as well as an understanding of the concept of behavioral synchrony. Behavioral synchrony (two dolphins acting together) was carried out effectively for behaviors directed by a trainer and for self directedbehaviors. The dolphins understood the referring function of the human pointing gesture,possibly as a generalization from the referring function of their echolocation beam. Self-awarenesswas demonstrated in two domains: the dolphin’s conscious awareness of its own recent behavior, and its conscious awareness of its own body parts when symbolically referenced. This suite of findings attest to the remarkable flexibility and extensibility of dolphin cognition and reveals cognitive competencies that surely aid the dolphin’s effective functioning within its complex social and ecological milieu.