Flashes having durations of 10, 20, 50, and 100 msec were matched in brightness to an adjacent 200-msec standard. When the standard and test stimuli terminated together, the results confirmed earlier demonstrations of the Broca—Sulzer phenomenon. Different functions relating the growth of brightness to duration were generated, however, when the flashes matched to each other had coincident onsets or coincident mid-durations. The matches made with stimuli terminating together were shown to exhibit transitivity: Targets which are as bright as a standard are approximately as bright as each other. Finally, an effect of relative luminance on apparent temporal position is described.
DAVID H. RAAB and ELI OSMAN, "Effect of Temporal Overlap on Brightness Matching of Adjacent Flashes," J. Opt. Soc. Am. 52, 1174-1178 (1962)