Two pulses seen as three flashes: a superposition analysis.
If a single brief light pulse follows the offset of a light field by 0.1-0.3 sec, the pulse is seen as a double flash. This "double flash effect" is a suprathreshold phenomenon: the pulse must exceed detection threshold by 10 times or more for this temporal illusion to occur. A special case of this effect is demonstrated here: two brief, high-luminance pulses separated by 0.1 sec appear as three flashes. In a superposition analysis, hypothetical impulse response functions were added together with various delays to model flash perception. A biphasic impulse response (congruent with threshold flicker and pulse sensitivity) fails to predict perception of three flashes from two pulses. The analysis instead suggests that the visual response to a suprathreshold pulse has several alternating phases of excitation and inhibition.
Department of Psychology, Loyola University of Chicago, IL 60626.
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RW
Bowen
D006801:Humans; D008960:Models, Psychological; D010775:Photic Stimulation; D011601:Psychophysics; D013597:Systems Analysis; D013997:Time Factors; D014796:Visual Perception / Q000502:physiology*