The Plastic Brain of Taxi Drivers

What’s special about London taxi drivers? They have enlarged brains.

They’re not mutants. If you want to become a cabbie in London, you have to undergo a daunting test called The Knowledge. To pass, you must be able to plot the shortest route between any two of the city’s 25,000 streets, and point out any relevant landmark along the way (there are about 20,000 in all). Preparing for this mind-boggling endeavor takes three to four years, spent mostly driving around in a scooter with a map placed on the handlebars – remember that if you spot one in the city, it makes for a good story.

Fewer than 35 percent of applicants are granted a license, not surprisingly. What’s surprising is that London cabbies are responsible for disproving one of the longest-standing foundations of neuroscience: that the brain, unlike other organs, stops growing shortly after childhood and is incapable of spawning new neurons. A study conducted on 79 training cabbies had them undergo an MRI scan after three years of learning London topography. Their posterior hippocampus, an area of the brain involved with spatial navigation, was found to have acquired additional grey matter: it was, on average, 7 percent larger than before the training.

This phenomenon, the brain’s ability to rearrange itself and change its physical structure, is called neuroplasticity. It’s one of many reminders of how little we know about the human brain. Recent research from Sweden shows that this growth is linked to specific types of activity. This time, MRI scanners were used on interpreters learning a new language from scratch and comparing them to cognitive science students: while organs in the control group remained unchanged, over just three months the interpreters showed growth in the hippocampus (again) and in the cerebral cortex, which is quite understandably involved with language. This confirms previous research that revealed how bilingual children have superior brain functionality in some areas, and how being bilingual can delay the onset of degenerative brain diseases like Alzheimer’s.

It seems you can teach an old dog new tricks. But when it comes to the brain, not everything has a tangible effect. What about those Brain Training games, then? Nintendo and other companies maintain that by playing them regularly you can “keep your brain young”, citing dubious research. It’s a good marketing effort and by no means the worse kind of manipulation of science, but sadly it is not true. Christopher Chabris and Daniel Simons dismiss the issue in their brilliant book, The Invisible Gorilla: «If you think that doing Sudoku will keep your mind sharp and help you avoid misplacing your keys or forgetting to take your medicine, you’re likely succumbing to the illusion of potential. Unfortunately, people who do more crosswords decline mentally at the same rate as those who do fewer crosswords. Practice improves specific skills, not general abilities».

In other words, what you get by playing Brain Training is that you get better at Brain Training. But there is a very easy way to improve your mental abilities, and it’s got nothing to do with puzzles. It’s called exercise. Engaging in physical activity increases production of a protein that keeps nerve cells healthy, giving you better mental skills. This has been proven by different studies on humans and rats, as you can read in this New York Times article, opened by a very odd illustration.

For both rodents and men, walking or running for just a few hours a week improves cognitive functions and, of course, physical fitness. And people who exercise actually have larger brains in later life. On the other hand, data reveals that sitting for more than three hours a day can shorten your life span by as much as two years. So, say goodbye to “Dr Kawashima” and get out of that chair. Your brain will be grateful.

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