Some properties of the double-flash illusion.
When a field of light (an inducing field) is extinguished, and a subsequent probe pulse is presented (5-msec duration, interstimulus interval of 80-320 msec), the single probe pulse appears to be a double flash. We measured the frequency of seeing this double-flash illusion when it was induced by high-contrast flickering fields. The illusion is dependent on inducer-field frequency, showing a major peak and, for some interstimulus intervals, subpeaks. There are notable interobserver differences in the frequency location of the peaks. We evaluated whether the results represented the transient response of a mechanism analogous to a single-harmonic oscillator. A second experiment compares the threshold illuminance for detecting the probe pulse with the illuminance above threshold required to see the double-flash illusion. The illuminance required for a double-flash threshold is high, being 7-20 times the illuminance required for pulse detection.
D000328:Adult; D000360:Afterimage; D004056:Differential Threshold; D006801:Humans; D007088:Illusions; D008297:Male; D009903:Optical Illusions; D010775:Photic Stimulation / Q000379:methods*; D013997:Time Factors