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Name:  Scott
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I set up a science experiment to test hand-eye coordination. My hypothesis was that 2 eyes are better than one. I used an electrical circuit with copper wire for a path and a wire with an open loop. I had my subjects try to go through the copper 3 times with both eyes open, than 3 times with one eye closed. Everyone did better with both eyes open. Although, my idea was that this would be the case, I am finding it difficult to explain why this would be. I know it has something to do with depth of vision, but I cannot explain it fully. It would really help me with my project if you could give me some ideas. I have looked things up in encyclopedias but they make it all sound too complicated. I would be really grateful if you could give me a simple but scientific answer.

Dear Scott,

What you have determined is called 'stereovision'. It can be explained in the following way: your left eye sees an object at a near distance from a slightly different angle than your right eye. In the brain, both visions are combined and overlapped. That would result in a double picture, as if two photographs were superimposed that were taken by moving the camera 1 inch left or right. Instead of a double vision, your brain has learned to melt this into one picture, and the 'double lines' are interpreted to tell you approximate distances: that is how you see depth at a near distance.

By the way, approximately 10% of people do not have stereovision, because one eye is bad, blind, or the brain has not learned to overlap the pictures. They see as if you were looking with one eye only. Many of these people would not even know they have no stereovision, because we are intelligent enough to learn how to deal with this minor disability.

A hawk without stereovision would not know how far apart his prey was, and by diving for it he may hit the ground with such force that it could kill him. For many animals stereovision is required to survive.

Dr. Wassenaar

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