It’s research that should be a bit reassuring to the rest of us.
The brains of London’s cabbies are particularly interesting to study because of the monumental 140-year-old requirement for the job: Each cabbie must memorize what’s known as The Knowledge — the locations of the 25,000 streets and 20,000 landmarks and other points of interest within a six-mile radius of Charing Cross, a junction of roads traditionally considered the center of London.
Learning the Knowledge is a grueling, multi-year effort, and more people fail the test than pass it. As one London cabbie says of the process: “I wouldn’t put people in prison. I’d make them do The Knowledge.”
Eleanor Maguire, a professor of cognitive neuroscience at the University College London, has been studying the neurological makeup of London’s cabbies for more than a decade. Her past research has shown that these men’s brains are different from those of the rest of us. Specifically, their hippocampus, an area of the brain involved with spatial memory (among other things), is much larger.
She also discovered that the longer the men have been driving a cab, the larger their hippocampus. But when they retire, their hippocampus shrinks back to a normal size.
As Yong explains in his blog article, “An enlarged hippocampus is a rare feature. You don’t see it in doctors who gain vast amounts of knowledge over many years. You don’t see it in memory champions who have trained themselves to remember seemingly impossible lists. You don’t see it in London’s bus drivers who have similar driving skills but work along fixed routes. Among all of these groups, only the London cabbies, with their superb spatial memories, have swollen hippocampi.”
Of course, Maguire’s findings raised the “chicken-or-egg” question: Do the men’s hippocampi enlarge from studying The Knowledge or do men pass the test because they have bigger-than-average hippocampi to begin with?
Maguire’s latest study, published recently in the journal Current Biology, suggests an answer. Writes Yong:
[Maguire and her colleague Katherine Woollett] scanned the brains of 79 wannabe drivers who had just started their training. Three to four years later, they did the same thing. By this point, 39 of the trainees — just under half — had earned their license. The rest had flunked out. The Knowledge is not easily won.
At the start of the study, the trainees had the same memory skills as each other, and 31 men with no aspirations of being cabbies. Everyone’s hippocampus was on a similarly level playing field. The second time round, things had changed. Woollett and Maguire found that the hippocampi of the qualified cabbies had grown in size, especially the back part. They were now significantly larger than those of either the failed trainees or the men who didn’t take part. The cabbies also outperformed their peers on spatial memory tasks.
This is the strongest evidence yet that the training that London cabbies undergo is directly responsible for the changes in their brain.
Why studying for the Knowledge has such a marked impact on the size of the hippocampus is unclear, but, interestingly, as Yong points out, the hippocampus is “one of only two parts of the brain that makes new neurons throughout our adults lives.”
And that’s why this research has implications for the rest of us.
“We’re in a situation where people are living longer and often have to retrain or re-educate themselves at various phases in their lives,” Maguire told Yong. “It’s important for people to know that their brains can support that. It’s not the case that your brain structure is fixed.”
You can read Yong’s post about Maguire’s research on the Discover Magazine website. You can also watch this video of an affable London cabbie describing (while driving) how he went about studying for The Knowledge (and how he wouldn’t want to have to do it again):