Everyday, when I leave work, I take the stairs because I don’t want to get trapped in the elevator on “my time”. Anyway, while I was walking briskly down the stairs, my eye started to itch, so I started to rub it while I was continuing on my way. That’s when I almost fell down the stairs. I’ve heard that people with one eye have no depth perception, and I thought I had just experienced this through a non-scientific experiment. As I continued down the stairs, with both eyes unhindered, it finally came to me. The question I know you would answer because it’s better than all of the others I’ve ever sent.
If one-eyed people have no depth perception, why do people often take aim (while shooting a gun or a ping pong ball in the Grand Prize Game) at something with one eye closed? Doesn’t that increase the chances of missing the target?
It’s not strictly true that one-eyed people have no depth perception. It’s just greatly impared. Comparing the images from the right and left eyes is only one of the ways that the brain has of judging depth.
(For example, you get a parallax effect even with only one eye when you are moving. You also get depth information from the difference in focus between near and far objects. And there are other minor depth cues beyond these.)
You close one eye while aiming because aiming isn’t about judging distance, but about pointing something in a particular direction. You sight along the barrel of the bb gun (or whatever). If you used both eyes, the input from the eye that’s not in line with the bb gun would interfere with the input from the eye that is.
I think you’ll find that if the game involves throwing something in an arc (like ring toss) people keep both eyes open.
When aiming at a target, the absolute bearing (or direction) is much more critical than depth perception. If the brain has to interpret two slightly different pieces of information, it’s harder to correlate. Also, consider the fact that the sight on a rifle is not exactly built for viewing with two eyes at the same time.