Thursday, February 3, 2011

Hole in the Hand

Our brain is a massive computer, yet sometimes it can get a bit confused.  I’m sure we have all called people by the wrong name, we can’t remember where we left our keys and the classic, we say “turn right” when we mean “turn left”.
This is a clever little demonstration that takes advantage of how images travel to our brain.
1. Take a piece of paper and roll it up length ways so you can look through it like a telescope.
2. Hold it in your right hand and look through it with your right eye.
3. Just relax and keep looking forward.
4. Now bring the left hand up in front of your left eye. Holding it close to the tube, move it towards your left eye slowly.  It should appear as if you have a hole in your left hand.
Why does this happen?  Well, because the two eyes that we have are like cameras which film two slightly different views.  The information is sent to our brain from each eye down each retina nerve. The brain then processes this information. 
However, in this case things go a bit wrong.  The brain gets two images, one of a hand and one of a hole.  In the attempt to make sense of it, the brain puts them together as a hole in the hand.
Yes, we have successfully tricked our brain!  But this does not mean the brain is stupid.  The brain is actually being super clever, it sees a hole in your left hand but the nerves in your hand are also sending messages to you brain.  They are saying “hey brain, I’m fine, there are no holes here”!  Rather than use energy to correct it, the brain will just carry on.
Hope you have enjoyed this Science in a Blog.