PERCEPTION AND GENERALIZATION OF FREQUENCY CONTOURS BY A BOTTLE-NOSED-DOLPHIN (TURSIOPS-TRUNCATUS)

A single adult female bottlenose dolphin was tested in a series of per ceptual studies. On each trial, 4 sine-wave tones were presented that contained a falling frequency contour or some other contour. There wer e several frequency-transposed exemplars of each contour type in each experiment. The dolphin discriminated contours at a level significantl y greater than chance in all experiments. In the 1st 2 experiments, th e dolphin demonstrated only modest transfer to novel stimuli and a sen sitivity to the absolute frequency of stimuli. In the 3rd experiment, there was no effect of the absolute frequency of stimuli; in the 4th e xperiment, the dolphin successfully transferred the discrimination to novel stimuli drawn from the octave above the previously heard range. These results demonstrate dolphins' capability to perceive frequency c ontours, which may underlie the recognition of conspecific whistles.