Which description best matches the term autokinesis?

• A. A nighttime visual phenomenon where a stationary light appears to move due to crosswind effects.
• B. A daytime illusion of movement caused by glare.
• C. Nighttime visual illusion that a stationary light is moving, which becomes apparent after several seconds of staring at the light.
• D. A stationary light that remains fixed when viewed through a rotating prism.

Answer: (C)

Autokinesis is a nighttime visual illusion in which a stationary light appears to move after you have fixed your gaze on it for a few seconds. The key idea is that with no surrounding references in darkness, your eye’s tiny, normal movements and the brain’s interpretation of retinal input can create a perceived motion where none exists. The effect tends to become noticeable after several seconds of staring at a single light, especially a small, bright one against a dark background.

This is why the statement describing a nighttime illusion of a stationary light moving that only becomes apparent after several seconds of staring fits best. In daylight, glare can produce other visual effects, not autokinesis, and viewing through a rotating prism would produce a different optical phenomenon rather than this fixation-based illusion.