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After-Image

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AFTER-IMAGE, the immediate recurrence of a sensation, in like or opposite quality, after the removal of its stimulus. Al ter images are most prominent in vision. If a person gazes steadfastly at a small coloured object for half a minute and then turns his eyes away to a neutral background, he will notice a small coloured spot of complementary hue and brightness. These are called negative after-images. If the object was red, the after-image is bluish green; if it was emerald green, the after-image is pink., if it was dark, the after-image is light. Positive after-images re semble the stimulus in brightness and hue and usually last only a few seconds. They are favoured by intense illumination in the stimulus, occurring after the eye has been in the dark. Positive after-images occur for pressure, temperature, and the sensations of bodily movement and posture. There are no after-images from sounds or odours.

after-images