Conditioned Vocalizations as a Technique for Determining Visual Acuity Thresholds in Sea Lions

Science  31 Jul 1970:
Vol. 169, Issue 3944, pp. 498-501
DOI: 10.1126/science.169.3944.498


Aerial visual acuity and underwater visual acuity were measured in two sea lions (Zalophus californianus) by training them to emit click bursts if they saw a striped target or to remain silent if they saw a gray target. The closest grating spacings that could be resolved both in air and under water subtended a visual angle of 5.5 minutes of arc at a distance of 5.5 meters.