The temporal course of reduction of test-stimulus effectiveness under conditions of metacontrast was studied with two different suprathreshold brightness-matching procedures. (1) Test-stimulus luminance was varied to make apparent brightness of the test stimulus equal to the brightness of a constant-luminance reference stimulus. (2) Reference-stimulus luminance was varied to match the apparent brightness of a test stimulus maintained at constant luminance. Functions obtained from two observers when the test-stimulus luminance was varied were typical metacontrast functions with maximum reduction of test-stimulus effectiveness when the test stimulus preceded the background by 50 ms, and the shape of the functions was highly similar to functions obtained previously with a disk–ring stimulus configuration. Functions obtained by varying reference-stimulus luminance were highly variable both between observers and within observers. The difficulties encountered with this second method probably resulted from glare from high-luminance test and surround fields.
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