Abstract
The temporal course of reduction of test-stimulus effectiveness under conditions of metacontrast was studied with a suprathreshold brightness-matching procedure in which test-stimulus luminance was varied to maintain constant brightness. One purpose of this study was to determine the effects of surround diameter on the over-all amount of reduction of test-stimulus effectiveness. Two specific predictions concerning the effect of surround size on the temporal course of reduction of test-stimulus effectiveness were based on the notion of delays introduced in neural pathways mediating lateral inhibition. The typical metacontrast effect was obtained, i.e., maximum reduction of test-stimulus effectiveness occurred when the test stimulus preceded the surround by an appreciable interval. The amount of metacontrast increased with increasing surround diameter, but surround size had no consistent effects on the temporal course of reduction of test-stimulus effectiveness. Although the amount of metacontrast decreased with decreasing surround luminance, the stimulus-onset asynchrony at which maximum reduction occurred showed no consistent changes with decreasing surround luminance.
© 1969 Optical Society of America
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