Underwater Visual Discrimination by the California Sea Lion

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Science  26 Mar 1965:
Vol. 147, Issue 3665, pp. 1594-1596
DOI: 10.1126/science.147.3665.1594


Two captive sea lions (Zalophus californianus) presented with a series of size-discrimination tasks showed preferences for the smaller of two targets and gave virtually errorless performances despite changes in the form and relative size of the targets. Further tests revealed that they were capable of discriminating a size-difference ratio as small as 1.06:1.