Since the ideas of illusion, ambiguity and instability are relevant for my work, I've done some research in the optical-physical structure of such phenomena.





 Images derived from Fibonacci and the so-called 'Café Wall Illusion'

This is one of the principles I normally apply in the construction of my sculptures made from bricks placing them one on top of another.




Perceptual constancies are sources of illusions.

Colour constancy and brightness constancy are responsible for the fact that a familiar object will appear the same color regardless of the amount of or colour of light reflecting from it. An illusion of color or contrast difference can be created when the luminosity or colour of the area surrounding an unfamiliar object is changed. The contrast of the object will appear darker against a black field that reflects less light compared to a white field even though the object itself did not change in colour. Similarly, the eye will compensate for colour contrast depending on the color cast of the surrounding area.

Object consistencies. Like color, the brain has the ability to understand familiar objects as having a consistent shape or size. For example a door is perceived as rectangle regardless as to how the image may change on the retina as the door is opened and closed.Unfamiliar objects, however, do not always follow the rules of shape constancy and may change when the perspective is changed.

Future perception. Researcher Mark Changizi of Rensselaer Polytechnic Institute in New York says optical illusions are due to a neural lag which most humans experience while awake. When light hits the retina, about one-tenth of a second goes by before the brain translates the signal into a visual perception of the world. Scientists have known of the lag, yet they have debated over how humans compensate, with some proposing that our motor system somehow modifies our movements to offset the delay. Changizi asserts that the human visual system has evolved to compensate for neural delays, generating images of what will occur one-tenth of a second into the future. This foresight enables human to react to events in the present. This allows humans to perform reflexive acts like catching a fly or ball and to maneuver smoothly through a crowd. Illusions occur when our brains attempt to perceive the future,and those perceptions don't match reality. For example, one illusion called the 'Hering illusion', looks like bike spokes around a central point, with vertical lines on either side of this central, so-called vanishing point. The illusion tricks us into thinking we are moving forward, and thus, switches on our future-seeing abilities. Since we aren't actually moving and the figure is static, we misperceive the straight lines as curved ones.

Changizi said: "Evolution has seen to it that geometric drawings like this elicit in us premonitions of the near future. The converging lines toward a vanishing point (the spokes) are cues that trick our brains into thinking we are moving forward - as we would in the real world, where the door frame (a pair of vertical lines) seems to bow out as we move through it - and we try to perceive what that world will look like in the next instant."

Artists have worked with optical illusions, including M. C. Escher, Bridget Riley, Salvador Dalí, Giuseppe Arcimboldo, Marcel Duchamp, Oscar Reutersvärd, Victor Vasarely and Charles Allan Gilbert. Also some contemporary artists are experimenting with illusions, including: Octavio Ocampo, Dick Termes, Shigeo Fukuda, Patrick Hughes (artist), István Orosz, Rob Gonsalves, Gianni A. Sarcone and Akiyoshi Kitaoka. Optical illusion is also used in film by the technique of forced perspective.