One of my new favorite shows is Time Warp and last week they ran a show where they had a juggler on.  One of the hosts, Jeff, remarked that juggling has been shown to increase your brain size by 3%, and then they showed the juggler working with live, running chainsaws.  Not exactly the kind of think I'd expect someone with a bigger brain than me to attempt, but I googled it.  Turns out that juggling really may increase brain size.  Of course nobody has linked that to any increase in thinking power, especially since it seems localized to motor activity centers in the brain.  BUT I think it's really cool that our brains AREN'T just gelatenous gray masses that are developed when we grow, then only shrink and decay after adulthood.  Keep reading, keep exercising your brain, and keep trying to learn something new!!!