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Science 31 July 1970:
Vol. 169. no. 3944, pp. 498 - 501
DOI: 10.1126/science.169.3944.498
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Articles

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

Ronald J. Schusterman 1 and Richard F. Balliet 1

1 Stanford Research Institute, Menlo Park, California 94025

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.


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Corneal power and underwater accommodation in great cormorants (Phalacrocorax carbo sinensis).
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Science. ISSN 0036-8075 (print), 1095-9203 (online)