The Effect of Stimulus Amplitude on the Threshold of Fusion of Paired Flashes

Four experiments are described in which the threshold of fusion of paired flashes was measured. The intensity of the single flashes making up the pairs was varied independently. The results showed that when the first flash of the pair was the more intense, the threshold of fusion increased linearly as the difference in the log intensity of the two flashes. A proposal put forward to explain the results suggested the “noise” created by the first flash of the pair has to dissipate to a critical extent to allow the “signal” arising from the second flash to be detected.