The role of test pattern background hue in the McCollough effect

An experiment is reported in which the role of the spectral characteristics of the test pattern used in eliciting the McCollough Effect was explored. It was found that the effect is still observable when the test pattern, which is usually achromatic, is itself chromatic. Two chromatic test patterns were used and the McCollough Effect was measured by comparing colorimetric matches of the test patterns before and after inspection of red/horizontal and blue/vertical grids observed under the usual McCollough paradigm. One chromatic test pattern overlapped spectrally the energy distributions of the two inspection patterns while the second overlapped neither inspection color. The observation of the McCollough effect on such patterns was taken as further evidence in support of the conditioning model of the effect.