Flash Suppression

Flash suppression is a phenomenon of visual perception in which an image presented to one eye is suppressed by a flash of another image presented to the other eye.

To observe flash suppression, a small image is first presented to one eye for about a second while a blank field is presented to the other eye. Then a different, small image is abruptly shown, flashed, to the other, second eye at the location corresponding to the image to the first eye. The image to the first eye disappears, even though it is still presented, and only the new image is perceived. The new image to the second eye suppresses perception of the image to the first. For example, if a vehicle is shown to the left eye for 1 second, and then a face is abruptly flashed to the right eye, the observer consciously sees first a vehicle and then a face. Note that the face is seen while the picture of the car is still present. If the order of presentation is reversed, the order of percept is reversed. The phenomenon of flash suppression seemed to have been known since the 19th century. The phenomena was described by McDougall in 1901 (p598) and utilized for an EEG experiment by Lansing in 1964. In 1984, Jeremy Wolfe characterized flash suppression in a systematic psychophysics study.

Flash suppression is an example of perceptual illusions that render a highly visible image invisible and that are used to study the mechanisms of conscious and non-conscious visual processing (Koch, 2004). Related perceptual illusions include backward masking, binocular rivalry, motion induced blindness and motion-induced interocular suppression.

The brain basis of flash suppression has been studied using microelectrode recordings in the visual brain of the macaque monkey (Logothetis, 1998) and in the human medial temporal lobe (Kreiman, Koch & Fried, 2002).