We loved this story when we heard it on NPR's Science Friday...
ScienceDaily (Feb. 4, 2011) — A systematic review carried out by a team at the Peninsula College of Medicine and Dentistry has analysed existing studies and concluded that there are benefits to mental and physical well-being from taking exercise in the natural environment. Their findings are published in the research journal Environmental Science and Technology on February 4th 2011.
It turns out that doing mental puzzles (crosswords, sudoku, etc.) help build specific brain functions ( P is addicted to those) but only hiking or other outside exercise builds a better brain all the way around.
But then, as backpackers, we knew that we felt better, and thought better, after we returned from a backpacking trip.
Of course we knew. We backpack. Our brains are already bigger!