Kanizsa Square without Pacmen Created by Selective Edge Adaptation: Demos
presented at Vision ScienceS Society Meeting 2002
Fixate to the small dot in the center, and observe the low-contrast stimulus (test) presented between the high-contrast alternating stimuli (adaptation).
Short adaptation (3s) and test (1s) periods are simply repeated. The effect "Kanizsa square without Pacmen" is expected to appear after several repetitions (~15s).
Keep firm fixation during both adaptation and test periods. The overlap of the edges in the adaptation and test stimuli is essential. Shorter observation distances are recommended as they reduce displacement of edges due to eye movements.
The adapting stimulus is alternated (black-white) in order to reduce/cancel afterimages. The balance of the black and white for complete cancellation differs from person to person. Therefore, for some people afterimages may dominate after prolonged adaptation, and thus the illusion may not work.
Use higher color depth ("thousands" or "millions"). With 256 colors, the illusory edges may be "real", due to the way the image is compressed.
Macromedia Flash 5 or later is required (Ver. 4 may not work).