The dual role of chromatic backgrounds in color perception.

This investigation explores the color appearance changes resulting from a contmuously presented adapting field. In every experiment. an incremental mixture of red and green monochromatic lights was superimposed on top of a steady red background field. On each experimental trial the intensities of the red background and the red increment were fixed: the subject adjusted the intensit! of the green light so that the incremental mixture appeared a “pure” (neither slightly reddish nor greenish) yellow. In one experiment. the increment was a steadi& viewed thin annulus seen on a larger background: in another experiment the increment was identical to the background in size and retrnal location but was presented as a brief (l50msec) flash: in the final experiment the increment was a brieflv flashed thin annulus seen on a larger background. For any fixed. relatively dim background level the intensities of the red and green increments wre approximately in constant ratio over a nearly 1 lo, 0 unit range of test intensities. However. with more intense adapting fields the. green light to red light incremental intensity ratio decreased as the test intensity was increased. with the ratio asymptoting at high test Iekels to an adaptation-intensity dependent value. The empirical observations reject both bon Kries’ Coefficient Law and the notion that only spatial (and or temporal) transients contribute to color signals. The results are consistent with a “two-process” theory where the adapting field is assumed both to contribute directly to the chromatic signal and simultaneously to alter the amplitudes (but not shapes) of the spectral sensitivity functions associated uith the three receptor-types of color vision.