Echolocation sameness-difference discrimination by the Atlantic bottlenose dolphin ( Tursiops truncatus )

Abstract

A dolphin was trained to differentially respond to two simultaneously presented stimulus objects depending on whether the objects were identical or different. The development of the concept of sameness-difference was then examined by successively presenting novel stimuli. Once these transfer tests indicated concept development, concept formation was tested by presenting two pairs of novel stimuli. Following the successful completion of this test, sensory information was limited to the echolocation modality by requiring the animal to wear rubber eyecups. Animal performance continued at a high level and two further transfer tests were conducted, each with two novel stimulus pairs. Performance on the first test initially declined to below 70%, but rapidly recovered. Performance on the second test indicated perfect transfer with initial performance levels at 100%. All stimuli were constructed to be aspect independent and differences between pairs were made as obvious as possible by varying size, shape, and materials. Reflective characteristics were examined for both target strength and frequency cues using a monostatic sonar measurement system projecting a simulated dolphin echolocation pulse.