jd writes "There has been research for some time showing that London cab driver brains differ from other people's, with considerable enlargement of those areas dealing with spacial relationships and navigation. Follow-up work showed it wasn't simply a product of driving a lot (PDF). However, up until now it has been disputed as to whether the brain structure led people to become London cabbies or whether the brain structure changed as a result of their intensive training (which requires rote memorization of essentially the entire street map of one of the largest and least-organized cities in the world). Well, this latest study answers that. MRI scans before and after the training show that the regions of the brain substantially grow as a result of the training, and they're quite normal beforehand. The practical upshot of this research is that — even for adult brains, which aren't supposed to change much — what you learn structurally changes your brain. Significantly."