There is no way to properly categorize illusions, as in many cases there are several underlying mechanisms contributing to an effect. In addition, not all illusions are completely understood. Therefore, the following illusion demonstrations will be presented in old-fashioned categories (even though these categories are completely misleading). Many of the interactive demonstrations require java and shockwave plugins.
Impossible Figures and Objects. These charming impossible figures are spatially inconsistent and paradoxical, yet they can reveal important insights into how we interpret three-dimensional objects from two-dimensional images.
The Impossible Triangle The Impossible Trident
The Impossible Staircase Comprehensive Bibliography
Ambiguous Illusions. In some cases the constraints for interpreting a scene or motion are ambiguous. Your visual system can interpret the scene in more than one way. Even though the image on your retina remains constant, you never see an odd mixture of the two perceptions — it is always one or the other, although they may perceptually flip back and forth.
Figure/Ground Ambiguity Perceptual Ambiguity
Depth Ambiguity Talking Vase
Cast Shadow and Ball Barber Pole Illusion
Breathing Square Ouchi Illusion
Spinner Wagon Wheel Illusion
Line Motion Effect
Distortion Illusions. Illusions that distort an image’s size, shape, and length.
Size Constancy Illusions Poggendorf Illusion
Twisted Cord Illusion Cafe Wall Illusion
Fraser Spiral Muller-Lyer Illusion
Camouflage Illusions. We hope you can find these interactive demonstrations! What determines a figure from its ground?
Figure/Ground Hidden Bird
Funny Places. Tourist traps and extraordinary rooms! Balls and water flow mysteriously uphill and people grow and shrink right before your eyes.
Ames Room Anti-Gravity Houses and Hills
Plank illusion Floating Boxes
Stereo Illusions. The amazing world of 3-D.
Afterimages, Motion Aftereffects, Lateral inhibition. Mostly low level effects cause these effects. Images and colors that arenít really there. Spots before your eyes, and motion where there is no motion.
Black and white afterimage Color afterimage
Motion Aftereffect Hermann Grid
Scintillating Grid Filling-in Illusion
Color and Shadow Illusions. Amazing illusions of color and shadow.
Shadow illusion Adelson brightness illusions Shape from Shading
Facial Illusions. Illusions of expression.
Margret Thatcher Illusion Presidential Illusion.
Auditory Illusion. The famous illusion of circular pitch. The ascending scale seems to rise forever, but somehow keeping cycling like an M. C. Escher staircase. Shockwave required.
Auditory illusion Cross-Modal Interaction