The human brain is an amazing piece of flesh. While comprising only 2% of your body mass, your brain uses 20% of the available o2 in your blood stream. The brain can be mapped geographically, the most important functions of the brain are usually found nearest the center, having evolved first. Sight, for example, is interpreted at the back of the brain (which is why when you hit the back of your head hard, you see stars). Your brain uses your 5 senses to piece together the world around you. But our brain frequently "misinforms" us about what is going on around us.

Each of your eyes works like a lens focusing light onto the back of your eye where it is picked up by rods and cones. Rods are responsible for low light vision and see in black and white, while cones are responsible for high-resolution vision and see in color. The center of each eye is where the cones are focused, so the center of your vision is where you will get the highest resolution "sight." Your true high-resolution sight has its limit at about the size of your thumbnail at arms length, after that your vision is low resolution and almost entirely black and white, although you seldom realize it. The optic disk is on the back of the eye, and it is where the optic nerve connects to your eyes. This optic disk causes us an interesting problem.

Did you know that each of your eyes has a blind spot? The optic disk on the back of our eyes contains no rods or cones, so all the light that falls on it doesn't register. You can test this easily enough right here on your monitor. Cover one eye with your hand, and then look at the Z on the left. Move closer while staring at the Z on the left side, the x's on the right will disappear from your peripheral vision. If you move even closer, you should see the x's appear again.

                            XXX                   
      Z                     XXX
                            XXX
                              


You don't usually notice these "holes" because your eyes compensate for one another. Our brain lies to us, and fills in the information that should be there. it takes the white area of the screen, and covers the blind spot with it. Your brain will also complete lines that cross this blind spot.

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                            XXX                   
      Z                     XXX
                            XXX
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It's a bit harder to see on your monitor, you might want to draw this one out on paper. If you close one eye, and look at the Z, you can move forward until the X's are in your blind spot. Then, you should see the line complete itself from the top to the bottom. Your brain uses the data on the top and the data on the bottom to fake the line that you see.
Another example of your brain faking data can be seen when your eyes move rapidly. Your brain stops receiving data when your eyes move rapidly and they fake a view while your eyes move. You can test this by looking in a mirror. Stand six inches away from a mirror and look from eye to eye. You can't see your eyes move, you simply see them at the end points, but, get a friend to watch, and they can see your eyes move. A rare percent of the population suffers from a condition called akinetopsia. This makes it very difficult or impossible for them to register moving objects. As DejaMorgana pointed out, they are trained to see motion by turning their heads quickly so that the object appears stopped in relation to their view.

Visual disinformation is presented to us because our brains either can't or won't give us the raw data that our eyes see. Our brains don't lie to us because they want to, it's a mechanism designed to keep us alive. The key thing to remember, is that what you see isn't necessarily the same thing that is going on around you. Your brain frequently makes "guesses" about what is going on and the majority of people are totally oblivious to them. In addition to misinforming us, our brain influences our conscious decision making process to further it's own goals.

Special thanks to DejaMorgana for help with the content and format of the node.

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