6. The pitch that keeps going higher
Ever heard this tune before and wondered why the heck is it not reaching a conclusion? When is the beat going to drop? My brain hurts!
Well, not your fault. The rising Shepard tone or its counter the Shepard-Risset glissando are textbook-examples of auditory illusions resulting in an ever increasing or ever decreasing pitch in the standard sine wave sound, while is actually just looped post the first 3 seconds.
But auditory illusions are not the show stoppers when it comes to tricking our perception. The eye takes the cake here. Try this for example: Hold your thumb at arm’s length with the opposite eye closed and slightly move your thumb away without looking at it directly. At around 15 degrees you will lose your thumb. That is your corresponding eye’s blind spot.
But nothing except the thumb disappears, the background is totally intact. Or is it? In reality the background is not seen at all. Your eyes at a time focus only on a minuscule range in the field of view. If anything changes in the rest of our field of view, we would not notice it at all. The background is not exactly seen by the eye. It is recreated by the brain, with the memories that it has of the background.
P.S.: The list can keep going on and on