Taxi drivers-in-training in London are required to learn the layout of roughly 25,000 streets within a 6-mile radius of Charing Cross train station, near the north bank of the Thames River. They also have to memorize the locations of thousands of places of interest where a tourist or businessman might want to be dropped.
Generally, all of this takes a good driver three or four years to master – at which point, he bellies up for a set of rigorous examinations that half of the trainees fail. No city requires quite so much of its would-be cab drivers. To put all of this in perspective, this is just a piece of what London expects them to internalize:
Courtesy: Geographers’ A-Z Map Company Ltd.
London cabbies refer to everything that they must acquire from this map, and more, as "the Knowledge," a kind of shorthand for possessing a learned skill set that is equal parts memory, literal street smarts and spatial navigation. The whole process is a bit of wonder – especially now that research has concluded becoming a cabbie in London actually changes the structure of your brain.
London-based researchers Eleanor Maguire and Katherine Woollett, who’ve published their findings in the journal Current Biology, studied 79 male taxi trainees at the start of their training, and then again three or four years later after their licensing exams. Only 39 of them went on to qualify as licensed cab drivers, and so the researchers had three groups to compare: drivers who passed, those who didn’t, and a set of 31 male control participants. (Not all of the drivers who failed or dropped out of the training turned up a few years later to have their brains studied.)
At the beginning of the study, there were no significant differences among the groups on age, background, education or IQ. They had similar results on a series of memory and recognition tests. And MRI scans of their brains were essentially indistinguishable. This is pretty much the scientific definition of a level playing field.
"This means," the authors write, "that the groups started out on equal terms and that any changes that subsequently emerged would be due to acquiring 'the Knowledge.'"
The drivers who went on to pass the exam spent twice as many hours per week training as those who failed. And when everyone turned up for the same battery of memory tests a few years later, significant differences emerged. Qualified drivers were much better than participants from the control group at judging the spatial relations between different London landmarks. But they were significantly worse at recalling the design of a complex figure drawing, suggesting that as they honed new memory skills, less useful ones deteriorated.
Then the researchers looked at their brains. Unlike the control group, drivers who qualified showed increased gray matter in the back part of their brains, in the hippocampus that’s integral to our memory and spatial navigation skills.
The even weirder part: taxi trainees who failed the exam did not exhibit these same changes (which leads us to believe London could stop giving these onerous taxi exams and just photograph hippocampi instead).
This is all great trivia about cab drivers. But the authors suggest that the research has implications for the rest of us, too – especially in an era when the economy and structure of the work force are requiring many adults to master new skills later in life. There’s hope for life-long learners, even at the level of our most fundamental cognitive abilities. As the authors write:
That there are many thousands of licensed London taxi drivers shows that acquisition of ‘the Knowledge,’ and presumably the brain changes that arise from it, is not uncommon, offering encouragement for lifelong learning, and possibly a role in neuro-rehabilitation in the clinical context.
Photo credit: Luke MacGregor/Reuters