Among taxi drivers, scientists found more grey matter in the area of the brain associated with memory. "The mid-posterior hippocampus, is where black-cab drivers store a mental map of London, including up to 25,000 street names and the location of all the major tourist attractions."
I am reminded of an old joke here. A guy is selling brains and is approached by a guy who asks how much for Einstein's brain. He says, $100. He then asks for the price of a dumb blonde's brain. The guy replies, $100,000. Shocked, he asks why does the dumb blonde's brain cost more. Pat comes the reply, because it was never used. Ok Ok...a tad sexist but then it is one of those dumb blonde jokes so not necessarily true.