Värvijärelkujutused

Värvijärelkujutused, also known as successive color contrasts or afterimages, are optical illusions where the perception of a color is affected by the color that precedes it. When one stares at a colored stimulus for a period of time and then shifts their gaze to a neutral surface, a faint impression of the complementary color is perceived. This phenomenon is a result of photoreceptor fatigue in the retina.

The mechanism behind värvijärelkujutused involves the cone cells in the retina, which are responsible for color vision. When exposed to a specific color for an extended duration, the cone cells sensitive to that color become temporarily less responsive. Upon removal of the stimulus, these fatigued cells signal less strongly than the surrounding, unfatigued cells. This imbalance in neural signals is interpreted by the brain as the complementary color of the original stimulus. For example, staring at a red object for a while and then looking at a white wall will typically produce a green afterimage, as green is the complementary color to red.

The intensity and duration of the afterimage depend on factors such as the saturation and brightness of the original color, as well as the time spent gazing at it. Värvijärelkujutused are a common demonstration in art education and psychology to illustrate principles of color perception and the physiological processes involved in vision. They highlight the active and interpretive nature of how our brains construct our visual experience, rather than merely passively receiving sensory information.