OPTICAL CRITICAL DURATION AND CONTRAST THRESHOLDS IN THE FRESH-WATER FISH, LEPOMIS-MACROCHIRUS, AS DETERMINED BEHAVIORALLY

The high visual resolution of a fast moving object or an instantaneous image by animals requires that they have a low optic critical duratio n. The freshwater bluegill showed the ability to detect an image displ ayed for 3.2 mus at contrast 67.1. The same image was undetectable by the human eye. The optic critical duration and the contrast threshold in the bluegill were found to be 1/55 that of man. In terms of time sc ale and contrast, the visual ability of the bluegill seems far beyond that of a human, and it is more able to see approaching divers and fis hing gears in the scattering medium of freshwater lakes.