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They temporarily relieve boredom though too much can be mind-numbing as well.
Illusions occur within all of our five physical senses: sight, hearing, taste, smell, and touch. Of the five, visual illusions are the most common, well-known, and well researched.
An illusion is a distortion of the sensory perception, revealing how the brain normally interprets sensory stimulation. At least scientifically, that is how it is defined. But why dwell on the scientific side when you can just let yourself be awed (or bored) for a moment.
Visual Illusion
There are many types of visual illusions including those that are naturally occurring (mirage and rainbow). Showing samples for each will definitely take more than one posting. Instead, I will cite three that I personally find amusing.
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See more of Julian Beever's work here.
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If you focus on one wheel, that wheel stops while the rest apparently keeps on rotating. If you focus on another, the previous wheel begins to rotate.
This illusion has something to do with eye movement.
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See more Magic Eye samples here.
Auditory Illusion
My brother introduced me to this one. At first I never paid attention. How can an audio file be that interesting unless it is a full-length version of the "Hello Garci" tape?
Well, this is not a scandal recording. Rather, an ingenious recording created by a group experimenting on how our ear perceives sound.
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Listen to this amazing Virtual Haircut illusion by clicking on the vintage radio image on the right. I must warn you though; you NEED an earphone to appreciate this.
Touch Illusion
There exist very few examples of illusions under this category probably due to the fact that touch sensation is slower than that of vision and hearing.
For demonstration purposes, one can try this:
Immerse one hand in cold water, the other in hot water for about a minute or so. Then immediately place both hands in lukewarm water. The "cold" hand will feel that the lukewarm water is hot while the "hot" hand will feel that it is cold.