What can you see? Our perception of repetitive structures is prone to distortion. Look at the checkerboard on the left. The squares lie exactly next to or on top of each other horizontally and vertically. But if simple graphic elements are placed at the crossing points, this regularity is broken (Kitaoka, 2005, p. 66). Depending on the sequence of light or dark elements, wave-like displacements or bulges occur.

What can you do? The initial picture has a checkerboard pattern with two levels of gray shading as background. Light or dark crosses are alternately superimposed at the crossing points. Depending on the sequence of light and dark crosses, different patterns can be seen. With transp. you can change the transparency of the crosses. So 0 means no transparency. 100 means complete transparency, so that no more crosses can be seen. With delta you can change the thickness of the dividing lines between the squares. At which transp. and/or delta does the distortion disappear? pen can also be used to change the thickness of the cross and test its influence on perception.

There is more to see: You can carry out additional experiments if you change other key data in the program code. For example, other color combinations can be tested. This is done by the colouring of the stage as background, as well as the colours of the squares and the light and dark crosses.

Further possibilities are offered by other arrangements of the crosses. Please note the following: The chessboard consists of 12×12 fields and therefore 11×11 = 121 crossing points. To set the desired graphic elements in an endless loop, I use a simple coding. Here 0 means drawing a dark cross, 1 means drawing a light cross. with a no cross is drawn at all, with > the beginning of the line above is reached and with ! the loop is ended. The initial example then looks like this: 0110>1101>0110>1101!

A more complicated example looks like a bulge:

This is the corresponding code:
—-11>-10100101>1010110101>0101001010> 1010110101>0101001010>0101001010> 1010110101>0101001010>1010110101>

Replacing the crosses with other graphic elements offers further opportunities for experimentation. All that needs to be done then is to replace the crosses procedure, for example with stars, disks or dots.

Related topics: Münsterberg illusion, Café wall illusion

Kitaoka, A. (2005).Trick Eyes. Magical Illusions that will activatwe the Brain. New York: Barnes & Noble Publishing.