Abstract:

Rhythm is an important component of many natural communication systems, but it has rarely been the focus of laboratory studies of nonhuman species. Recent cognitive studies with a bottlenose dolphin confirm that a dolphin can discriminate among six different 14-kHz 4-s acoustic rhythms at 94% accuracy, and can transfer that discrimination across multiple frequency (93%) and tempo (16%--93%) shifts. In addition, a dolphin has learned to produce six different rhythms in an object-labeling paradigm. Original training required the dolphin to produce the rhythms using a pneumatic switch that led to the in-air projection of computer-generated tones. However, the dolphin spontaneously began to produce the rhythms vocally as well. To date, the dolphin has accurately labeled five objects with unique rhythms at 87% accuracy using the switch and at 83% accuracy using his own vocalizations. Confusions at the various tempos in the perception study and the variability of some characteristics and stability of others in the production study provide insight into how dolphins represent rhythm and have implications for natural communication in this species.