This is my animation of a Koffka ring (named after the Gestalt psychologist Kurt Koffka). It demonstrates in one simple package striking aspects of both gestalt and simultaneous contrast effects.

A little demonstration which is cause for both hope and despair.

This started out as a demonstration of a well-known old illusion, the "Hering illusion" (discovered in 1861 by the German physiologist Ewald Hering) — but ended up also showing a fascinating depth-perception effect.

This one also demonstrates a nice Gestalt effect.

This ball is on a roll.

This animation demonstrates the phenomenon of "Mach bands" (named after the discoverer, the Austrian physicist Ernest Mach).

This animation demonstrates the " Poggendorf illusion". 

This intriguing illusion is known as the "Kanizsa triangle" (see also my warped & animated 3D Kanizsa triangle) .

Here is an animation of a fascinating illusion, called the Sander illusion — with some accompanying provocative text. (The very last sentence in my text is probably untrue, or at least needs some major qualifications, but I'm leaving it in for now).

Here is an animated illusion which is very striking indeed, and from what I've read it is currently unexplained (it is called White's illusion and it contradicts the standard simultaneous contrast effect). However, I have an hypothesis which could explain it . . . later, later . . .

This is a twist on the above White's illusion — though with vertical stripes and color bars.

This two-image demo is known as the "Cafe wall illusion". (Note that there is no animation here by me — whatever creeping, undulating motion you see is a also an illusion, in addition to the "Cafe wall" illusion).

Some other fascinating demonstrations

This may perhaps be a little world-historical first: my warped & animated 3D Kanizsa triangle. To perceive the 3D, you must be able to "free-fuse" two images, as in viewing stereograms. Note how all five of the "objects" — the three dots and the two triangles — are "in space" and moving. The design contains a deliberate "3D plane collision" — but the triangle still holds up well. An amazing effect . (Yes, I'm rather pleased with this one. :-))

This experiment in depth-perception was inspired by the great perceptionist James J. Gibson's experiments with a "pseudo-tunnel".

This one will show you what Vermeer knew very well (though he admittedly knew a lot of other things, too).

This little trick of my own is not, in my judgment, an illusion (though many disagree), but it's still damn cool — as it demonstrates, believe it or not, the fundamental principle of all "realistic" painting (for more, see also the one on what Vermeer knew very well).

This will show you why Vermeer didn't do paint-by-the-number jobs.

This animation is a twist on the Adelson checker shadow illusion — but showing no perspective, no solid object, only a spotlight and a cast shadow.

This is another neat twist on the Adelson checker shadow illusion

This very striking 3D animation I have christened The Nordby Pile. To perceive it, you must be able to "free-fuse" two images by crossing your eyes, as in viewing stereograms.

This is not an animation, but a still image, and another "free-fuse" stereogram. I wanted to see how much depth it was possible to create with only static black shapes and no background. Quite a lot, it turned out.

A good example of the complimentary color contrast effect.

And here's another good example of the simultaneous color contrast effect.

And this is yet another good example of simultaneous color contrast, often referred to as the "fluting effect," due to looking like flutes, i.e., the concave edges of classical columns.