Becoming an official London cabbie is no small feat. To earn their “green badge,” they have to pass a difficult and comprehensive test of London’s 26,000 streets and the routes between them—which typically takes at least three years to complete. This intense study changes their brains: studies show that the hippocampus (a brain region closely associated with memory) of the average cabbie is significantly larger than in other people. That same brain region shrinks in people with Alzheimer’s. Now, researchers are now looking more deeply into the brains of London cabbies, with the hope of using their findings to improve early detection of Alzheimer’s.

More about it here, on The Washington Post (not the BBC! 😊)