Nicole Daskas Blog #5 Illusions and Perception
Optical Illusions and Systems of Perception
Nicole Daskas
As the eyes look at something, what is actually being seen is light bouncing off the image and entering the eye. Light is then turned into electrical impulses seen by the brain. Eyes are receiving information constantly; this never stops. This results in the brain trying to simplify what it is seeing to make up for its “processing lag” (Inside Science). Optical illusions play on this.
Optical illusions rely on humans’ perception of color and light to give a kind of false effect. This creates the feeling that either the mind or the eyes are playing tricks. For example, the image below is obviously still. However, it seems to be pulsating and spinning to the eye. This is known as a “psychedelic peripheral drift illusion. If the viewer focuses on the middle of the image, it appears completely still. However, if the eye focuses anywhere else the pattern moves. The brain perceives light values faster than in perceives dark values. For this reason, the discs are turning in the direction of lighter shades. Additionally, if the viewer blinks or shifts one’s focus, the perception is “reset” and shifts back to center.
This well-known optical illusion is a Hermann grid. Viewers are looking at pure black squares against a pure white background. However, many gray dots seem to appear at the intersections of the parallel white lines. This is because the eyes have cells that “collect from lots of different photoreceptors about light and dark values” (Inside Science). This information then bleeds over into other cells, so one perceives these gray ghost squares due to the image’s extremely high contrast.
This optical illusion is composed of light purple faded dots in a circle. There is a focal point in the middle shown with a black “+”. In a clockwise motion, one of the purple dots disappears. This blank space moves continuously around the circle. If the viewer focuses on the black plus sign in the middle, however, the blank space will start to appear as a light green dot. This is, once again, the mind “playing tricks”. When the brain sees something at one point and then again at another, it assumes that the object is in motion, even if this is not the case. Blurred objects located in humans’ peripheral vision will also start to disappear when the eyes are not located directly upon that object.
This is another optical illusion discovered by Richard Gregory in the early 70s. The lines here are actually parallel and completely straight. It is the tile pattern that makes the lines appear to slant diagonally. This pattern, when painted on a wall, is affected greatly by the grout lines between the tiles. If it is too thin or too thick, the illusion fails. The way the lines appear is due to the way neurons in the brain interact with one another and with lights and darks. The brain creates “a small scale asymmetry whereby half the dark and light tiles move toward each other forming small wedges. These little wedges are then integrated into long wedges with the brain interpreting the grout line as a sloping line” (Modern Met).
Comments
Post a Comment