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Why taxi drivers have bigger brains

Satellite navigation may have revolutionised travel for millions of us around the world, but for one small group of drivers it hasn't made any difference at all. London black cab drivers are renowned for getting around the UK's capital by memory alone, having to pass a test based on hundreds of different routes and thousands of waypoints. We talk to a cabbie to find out exactly what it involves.


Picture credit: Wong Chi Chiu

The Knowledge

With over 26,000 streets to learn, becoming a licensed London taxi driver takes a lot more than just driving skills. The routes drivers need to know form part of a test known as the ‘Knowledge', and at least one comprehensive study shows parts of driver's brains growing in size to accommodate all the information.

Chris Hanrahan is a London taxi driver, and explains that it took him a staggering three years to acquire enough knowledge to pass the, well, Knowledge. And although he first passed the test over 30 years ago, it still takes around the same amount of time to get to grips with London. "The level of knowledge that you need to acquire before they send you out to carry the public around here, there and everywhere is just as comprehensive as it ever was.”

It's such a comprehensive test, in fact, Chris points out that for every ten people who apply, only about two or three actually manage to get through.

The Knowledge itself is based around routes and points of interest, rather than just street names themselves. "The system to be a London cab driver has changed considerably, but you'll still be expected to have a geographical knowledge of hundreds of routes, and what they call points. Things like St Paul's Cathedral, Westminster Abbey, places of interest, restaurants, pretty much everything you can think of," says Chris.

All the things you'll find when using HERE apps, in fact, but this time stored in the human brain, rather than on smartphones, computers or in the cloud.


Picture credit: Elnur

Getting ready for the challenge

It’s a tough challenge, and one which has seen numerous ‘Knowledge schools’ pop up around London, in a bid to help budding cabbies get to grips with the city’s countless twists, turns and one-way systems. The schools will run through everything you need to know to pass the test, going through the questions currently being asked by examiners. “It’ll often be something that’s in the news – you may be asked about a journey based on something topical, for instance,” says Chris.

So how do drivers actually go about learning all the routes? Chris says he found it easiest to put pen to paper: “I wrote out every single route in longhand. It was a lot of paperwork , believe me! I wrote it out by hand because I found that doing it that way made it stick in my memory more than just reading it and trying to memorise it.”

Routes have to be explained in painstaking detail, including every junction and street along the way. “So when they ask you to drive from Crystal Palace to Alexandra Palace,” explains Chris, “it was always the stock reply: Leave on the left, Crystal Palace Parade, and so on and so on. You had to name every junction, name every turn, until you’ve set down in front of Alexandra Palace. If you get anything wrong, they’d say ‘no, that answer’s not good enough’.”

While sat-navs are now allowed in black cabs, Chris points out that most taxi drivers don’t bother, and adds: “Obviously the passenger wants to be taken where he wants to go, he doesn’t want to get dropped off two streets away with you saying ‘I think it’s up there somewhere mate but I’m not quite sure. It’s hammering with rain and you’re dressed for a night out, but I’m sorry I can’t help you anymore…’ That’s not what we’re about, you still need some experience and knowledge.”

So taxi drivers do have bigger brains…


Picture credit: Sebastian Kaulitzki

The brains of cabbies need to take on so much information, in fact, that research by Eleanor Maguire – a Neuroscientist at University College London (U.C.L) – suggests they grow accordingly, with her study showing parts of the brain’s hippocampi getting larger when getting to grips with the Knowledge.

Eleanor followed 79 aspiring taxi drivers for four years while they learned everything they needed to know about the streets of London, carrying out MRI (Magnetic Resonance Imaging) scans to measure the size of their hippocampi. With half of the potential cabbies passing the test, Maguire continued to run brain scans, and the results were startling. Those that passed performed far better in the tests the final time around, a stark contrast to the first series of tests where the hopefuls performed equally.

In her study, Eleanor explains:

“Taxi drivers had a significantly greater volume in the posterior hippocampus,” and that “the converging results from these two independent analysis techniques indicate that the professional dependence on navigational skills in licensed London taxi drivers is associated with a relative redistribution of grey matter in the hippocampus.”


Interestingly, it seems that the hippocampus grows purely to accommodate location information, and Maguire adds in her report:

“A basic spatial representation of London is established in the taxi drivers by the time The Knowledge is complete. This representation of the city is much more extensive in taxi drivers than in the control subjects. Among the taxi drivers, there is, over time and with experience, a further fine-tuning of the spatial representation of London, permitting increasing understanding of how routes and places relate to each other. Our results suggest that the “mental map” of the city is stored in the posterior hippocampus and is accommodated by an increase in tissue volume.”

We asked Alistair Greecy, another black cab driver, whether learning the Knowledge had made a noticeable difference to the way he learns things. “I really couldn’t tell you, but I do seem to be able to put things together a lot easier…” Sadly, being able to memorise thousands of streets and landmarks, along with hundreds of routes, doesn’t seem to make it that much easier to pick up other information, and Alistair adds: “I did try to learn Spanish, but I’m terrible!”

And as for the rest of us, struggling along with a smaller posterior hippocampus, there’s always HERE maps!


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