How Do Optical Illusions Work?
The term “optical illusion” is applied to what we think we see, to separate that from what is really happening. Because the brain receives certain information about size, color and so on, it interprets the information based on those details. But what is truly in front of our eyes might be slightly different.
Why is the message we get so different from reality? Most psychology texts and medical encyclopedia information explains it this way: There are three basic types of optical illusion – literal, physiological and cognitive. Let’s break these down a bit further.
Literal illusions are those that give us an image that is different from some object that we are actually viewing. Physiological illusions depend on the word “excess” – there is too much color or movement, for example. Cognitive illusions occur when the brain and the eye infer something without us realizing it.
Using one type of illusion might help us understand the overall process better. Physiological illusions happen when there is too much of something. If we see extremely bright light, such as when a camera flashes or lightning strikes, we might see what is known as an “after-image.” Think of this process as creating an image that is out of balance or that continues after the real image is gone.
With cognitive illusions we are inferring something about what we see, without realizing that we are doing it. One of the best examples might be the work of M.C. Escher, whose staircases and waterfalls are drawn so that we see different aspects at different times. (Wikipedia) Doctors and psychiatrists note that extreme cognitive illusions occur in people who have schizophrenia or have been influenced by hallucinogenic drugs.
If two objects are positioned so that the colors seem to blend or interchange we could be experiencing an optical illusion, especially if the colors are the same. If shapes appear distorted or the placement of objects makes them seem to differ in size we might be experiencing an optical illusion. (Think of the different black-and-white line drawings that trick our eyes in this way.)
Another good way to get some understanding of optical illusions is to think of the term “the hand is quicker than the eye.” In the eye, the nerves and the brain, cells receive and process images at different rates. We might see something for a split second that looks different from the real object. When a magician performs a sleight-of-hand trick our brain could register what appeared to happen a short time before or after it actually occurred.
Consider as well the confusion that occurs when a great performer thrills us with a card trick right at the table where we are seated. He or she is able to move two cards so quickly and so closely together that we see them as one, for instance. We simply don’t see the tiny difference in the thickness of two cards, as opposed to one card. Magicians are able to put small objects into pockets or transfer them from hand to hand more quickly than our eyes and brain can record the image.
That’s optical illusion.
Category: Technology