Sources of variability in apparent-contrast measurements made by brightness matching

The apparent contrast of backward- and forward-masked spatial sinusoids was measured by a brightness-matching technique suggested by Davidson (1966), designed to be free of artifacts associated with earlier matching methods. Data variability was relatively large due predominantly to (1) fluctuations in masking-interval duration, and (2) changes in the O’s criteria produced by the salient temporal and spatial differences between test and comparison fields. Several other potential sources of data variability were found to be negligible.