Whether it is a mirage or the voices in your head, all of us have experienced some sort of illusion. Illusions are not just limited to optical tricks. Some are matters of great enjoyment. Others are frightening. Which sort of illusion is your favorite?
The most well understood is the optical illusion. You know what you are looking at, but you are seeing something entirely different. Why does it work?
The eye has cataloged in your brain everything it saw. It frames what it sees in comparison to what you already know. When you see certain things, you expect them to result in something in particular or something congruent with what you know.
When you see lines in a particular order, you expect to see the bordered image as stagnant. When lines are curved, the eye sees motion. Fractal optical illusions appear to be in motion because of the proximity and shape of the lines and/or colors are not congruent with what the mind believes should exist.
Other pictures we see bring our attention to the part of the image which appeals most to us. These are the most classic of optical illusions. The two faces versus the vase is one of the most easily replicated visual illusions. Others are much more complex and, based on the viewers’ past experiences, show more detailed images in the fore versus the background.
Most tactile illusions are completely imaginary. When limbs (or teeth) are removed, amputees report feeling pain in the missing limb. When you cross your fingers and run them over the bridge of your nose, you are imagining the second nose you think you feel with your fingers.
The thermal grill illusion best explains how these happen. A grill of metal rods alternating hot and cold, 104°F and 68°F (40°C and 20°C), is presented. When touched, it appears to be hot enough to burn, but only if the person touches both a hot and cold rod.
If only hot is touched, only warmth is felt. Likewise, if only a cold rod is touched, only coolness is felt. The illusion occurs when the conflicting signals are sent to the brain resulting in the misconception. The contrast of the warmth and coolness tricks the brain into perceiving far higher temperature. In the mind, the two cannot coexist.
Auditory illusions are tricks between the ear and the brain. The Shepard’s tone is common in sound effects, tricking the brain into hearing an unending fall or an unfathomable ascent. It is called the sonic barber’s pole.
A well-known entertaining auditory illusion is ventriloquism. By engaging the brain in the movement of the dummy’s mouth, the mind transfers the sound of the ventriloquist’s voice to the dummy. The artist’s true ability is producing intelligible words without noticeably moving the mouth, which would break the auditory illusion by drawing the eye to the correct mouth.
Some illusions are carried by illness. Those who have lost use of certain taste buds can get the illusion of the taste of their favorite foods by similar textures in the mouth touching the tongue. The nose can be tricked into many different smells by the mention of the names and olfactory stimulation. Let someone mention sulfur and rotten eggs (or equally significant smell) just before you take a deep breath.
Migraine sufferers and fatigued people experience optical illusions. These hallucinations are chemical derivatives of pain and the body’s self-preservative instinct. When your head throbs, you will see scintillating scotomas. The spots or zigzag images dance or swirl in a outward-spiraling, counterclockwise motion.
When you are very tired, you will see gremlins. These are not the furry monsters of movies, but illusory shadows and flashes of light your mind creates to focus your attention to keep you awake.
Hallucinations are symptoms of some mental illnesses. They range from simple fantasy characters to elaborate worlds seen and/or heard only by the patient.
What all illusions have in common is they are illogical. They are tricks which end in something other than what the mind knows should exist. The mind has the power to overcome the illusion, but sometimes, it is just outright fun to be fooled.
What are some of your favorite illusions? Have you ever seen a ventriloquist perform? Feel free to leave links to your favorite optical illusions.
(c) Ann Marie Dwyer 2012
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