Aren’t optical illusions fascinating? What are they, anyway?
An optical illusion is when your vision sees something different from objective reality. The eye gathers information and sends it faithfully to the brain, but something in the image causes the mind to misperceive the scene. Some optical illusions are physiological – they result from overstimulation of the brain. This can occur from repetitive or intense images, often as a result of competing stimuli, like red against green or grey dots at the intersection points of a white grid on a black background. Perception is altered by some sort of physiological imbalance. The result is to see things that aren’t there, or to not see things that are.
Cognitive illusions result from unconscious inferences due to ambiguity, distortion, paradoxes, or the imagination of the viewer (schizophrenics are prone to this last form). Paradox illusions are especially popular, as witnessed by the demand for the pictures of M. C. Escher. Ambiguous illusions arise from pictures or objects in which two different perceptions of the image coexist and switch back and forth. Look at the flower paintings of Octavio Ocampo to see some good examples. For instance, his painting of leaves resembles the head and torso of a nude, and you perceive both images in a constant alternation of perception.
The need for the brain to organize perceptions has led Gestalt psychologists to develop interesting test pictures that cause viewers to create meaning from ambiguity. Famous optical illusion tests include the Duck-Rabbit illusion, in which a left-facing duck transmogrifies into a right-facing rabbit, and then back again. The Kanizsa Triangle compels the viewer to interpret negative space as a white triangle floating in the foreground. Humans have evidently evolved to see forms and edges, sometimes even when they are not there. The Ponzo illusion causes viewers to misinterpret the relative length of two equal horizontal lines due to their juxtaposition within a field of converging parallel lines. Film animation is completely dependent on optical illusion – 24 frames of individual drawings per second equals a moving picture to the human observer.
One of the coolest illusions is that of the Spinning Dancer, who appears to be turning clockwise and counter-clockwise simultaneously. Scientists theorize that the brain gets confused when it is presented with unusual situations, ones that are different from the way the brain was trained to judge movements. Whatever the explanation, optical illusions can be fun or frightening, but always fascinating.