The relation between field size and decrease in critical rate (CFF) of a flickering field stereoscopically superimposed on a contralateral steady image is reported. Two designs were used. In one, luminances spanning a 6-log-unit range were variously combined in fields which were both 1.5°, 3°, or 9° or in which the flickering field was the smaller image. The other design utilized the same luminance combinations but the flickering image was 6° and the adapting field was varied from 9° to 1.5°. Results indicate that if both fields are initially 1.5° then increasing the size of both fields or of just the adapting field does not further decrease CFF. But if the size of the flickering field is increased to 6°, CFF of the 1.5° central portion of the flicker field which appears superimposed on the 1.5° adapting field is markedly reduced, while the flickering annulus shows the threshold reduction expected with equal-sized 6° fields. The center of a fairly bright 6° flicker field viewed with an adapting field 4.5° or less and flashing at low frequencies appears steady. Several interpretations of the results (macular dominance, corresponding points, monocular cross-regional interaction) are discussed.
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