Your eyes send the brain a flat patchwork of light. Your mind turns it into objects, groups, and depth. Pick a demo, then flip the switch to add or remove the cue. The dots and lines themselves do not change. Only what you perceive changes. In the last tab, measure how strongly an illusion fools you.
Pick a demonstration
Flip the switch to turn the cue on and off.
Illusions & Gestaltchoose a demo to begin
Drag until the bottom line looks as long as the top line