A study by neurologists at University College London found that the hippocampus, the part of the brain responsible for spatial navigation, of a London cabby is significantly larger than those in the rest of the human population—a result of the intense memorization and route-finding undertaken while doing The Knowledge.

The study involved taking regular brain scans of Knowledge-seekers undergoing their training and comparing them with scans taken of a control group of people who had no interest in becoming cabdrivers.

At first, the hippocampi of all the study subjects were of similar size, and all subjects performed similarly on routine memory and route-finding tests. By the end of the study, though, those who’d passed The Knowledge had larger hippocampi, and the longer they worked as cabbies, the larger their hippocampi became.

“We don’t know what is changing in the hippocampi of taxi drivers,” says Eleanor Maguire, who led the study. “Whether it’s new neurons that are being produced, new connections between neurons, proliferation of other cell types, or all three.

—From “For London’s Cabbies, Job Entails World’s Hardest Geography Test,” a special feature for National Geographic by Roff Smith. Smith’s piece chronicles the intensive process necessary to obtain a London taxi license.

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Photo: Grepnold, Flickr