Dolphin (Tursiops truncatus) echoic angular discrimination: effects of object separation and complexity.
A bottlenose dolphin was tested on its ability to echoically discriminate horizontal angular differences between arrays of vertically oriented air-filled PVC rods. The blindfolded dolphin was required to station in a submerged hoop 2 radial m from the stimuli and indicate if an array with two rods (S+) was to the right or the left of a single rod (S-). The angular separation between the two rods (thetaw) was held constant within each experiment while the angle between the S+ and the S-stimuli (thetab) varied to produce angular differences (deltatheta= thetab-thetaw) ranging from 0.25 to 4 degrees. In experiment I, thetaw was maintained at 2 degrees and in experiment II, thetaw was maintained at 4 degrees. Resulting 75% correct thresholds (method of constant stimuli) were 1.5 and 0.7 degrees, respectively. The two main findings of this study are: (1) decreasing the number of targets does not aid in localization, and (2) increasing the space between the rods enhances localization. Taken as a whole, the experiments suggest dolphins have a well-developed ability to resolve spatial information through sonar.
Branstetter
Brian K
BK
Psychology Department, University of Hawaii, Manoa, Honolulu, Hawaii 96822-2294, USA. branstet@hawaii.edu
Mevissen
Sonja J
SJ
Pack
Adam A
AA
Herman
Louis M
LM
Roberts
Scott R
SR
Carsrud
Lea K
LK
D000162:Acoustics; D000818:Animals; D001307:Auditory Perception / Q000502:physiology*; D050681:Bottle-Nosed Dolphin / Q000502:physiology*; D004193:Discrimination Learning / Q000502:physiology; D004455:Echolocation / Q000502:physiology*; D004777:Environment; D008297:Male; D008954:Models, Biological; D009949:Orientation / Q000502:physiology; D013028:Space Perception / Q000502:physiology*