Hi, I thought you may like this Mentalrobics exercise from Braingle.com:
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Only 10% of Your Brain

It is a myth that humans only use a fraction of their brains. Even though scientists are still trying to unravel the mysteries of the human mind, every part of the brain is known to have a function. From an evolutionary point of view, larger brains would not have developed if there had not been an advantage to do so.

The origins of this myth are unknown, but it might have originated from a researcher named Karl Spencer Lashley who lived about a hundred years ago. He removed parts of the brains of rats and showed that they could still perform certain tests. The problem with these results are that the rats were only tested on tasks that required the parts of the brain that had not been removed. If the rats had been given other tests, they would have certainly failed.
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For more mind exercises: http://www.braingle.com/mind/