antisilmänjälki

Antisilmänjälki, a Finnish term, translates literally to "anti-eye mark" or "anti-afterimage." It refers to a phenomenon where an afterimage is perceived as the complementary color of the original stimulus. For example, if one stares at a bright red object for a prolonged period and then looks at a white surface, they might perceive a green afterimage. This occurs due to a process called chromatic adaptation in the eye's photoreceptor cells, specifically the cone cells.

When exposed to a specific color, the cone cells responsible for detecting that color become fatigued or desensitized. Upon shifting gaze to a neutral background, these fatigued cones are less responsive. The brain then interprets the signals from the other, less fatigued cone cells, resulting in the perception of the complementary color. This is a well-documented visual illusion, demonstrating how our perception of color is not solely based on the incoming light but also on the state of our visual system. Antisilmänjälki is a common demonstration used in psychology and optics to illustrate the principles of color vision and adaptation. It is a temporary effect and disappears as the cone cells recover their sensitivity.