Abstract
The purpose of this investigation was to determine whether or not human perception of two equal flashes of colored light is a function of the interstimulus interval. Thirty subjects with normal color vision were presented with two 5 ms flashes of light, the first at 697 nm (red) and the second at 565 nm (green). The interstimulus interval was varied from 5 to 100 ms. When the interval was less than 30 ms, subjects reported seeing yellow flash. From 30 to 50 ms, subjects reported seeing only a green flash. Above 50 ms, subjects were able to identify two flashes, one red and one green. These results constitute a contradiction of Bloch's Law, which states that for interstimulus intervals less than 70 ms, stimuli are summed to produce perception. The implications of these results on a model for human color vision are discussed.
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