In her earliest studies, Maguire discovered that London taxi drivers had more gray matter in their posterior hippocampi than people who were similar in age, education and intelligence, but who did not drive taxis.
In other words, taxi drivers had plumper memory centers than their peers. It seemed that the longer someone had been driving a taxi, the larger his hippocampus, as though the brain expanded to accommodate the cognitive demands of navigating London's streets.
But it was also possible that The Knowledge selected for people whose memory centers were larger than average in the first place. To find out which possibility was more likely, Maguire and her U. For the sake of comparison, Maguire also measured brain growth in 31 people who did not drive taxis but were of similar age, education and intelligence as the taxi trainees.
At the start of the study, all of the participants had more or less the same size hippocampi. Maguire also made sure that the aspiring cabbies and non-taxi drivers performed similarly on tests of working memory and long-term memory. Four years later 39 of the 79 trainees had earned their licenses; 20 trainees who failed their exams agreed to continue participating in the study.
When Maguire gave the successful and disappointed trainees the same battery of memory tests she had given them at the start of their training, she found that drivers who earned their licenses performed far better than those who failed—even though they had performed equally four years earlier. And MRIs showed that the successful trainees' hippocampi had grown over time. There are several ways to explain the ballooning hippocampus. The hippocampus may grow new neurons or hippocampal neurons may make more connections with one another.
Non-neuronal cells called glial cells, which help support and protect neurons, may also contribute to the increase in hippocampal volume, although they are not generated as quickly as neurons. The successful trainees did not perform better on all tests of memory, however. Licensed taxi drivers did worse than non-taxi drivers on a test of visual memory called the Rey-Osterrieth Complex Figure Test : The subject is asked to study what looks like a dollhouse designed by a loony architect, full of superfluous lines and squiggles, and sketch it from memory 30 minutes later.
Maguire thinks that The Knowledge may enlarge the hippocampus's posterior rear at the expense of its anterior front , creating a trade-off of cognitive talents—that is, taxi drivers master some forms of memory but become worse at others. In her earlier work, Maguire found evidence that, whereas the rear of the hippocampus was bigger in taxi drivers, the front was usually smaller than average.
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Skip to content You currently have JavaScript disabled in your web browser, please enable JavaScript to view our website as intended. There are no dropout figures, but each year Transport for London TFL usually licenses between a quarter and a third of the number of applicants, so we can safely say that most who start the Knowledge never finish it. The average "Knowledge Boy" or, occasionally, Girl spends three or four years covering around 20, miles within a six-mile radius of Charing Cross, out on their moped come rain, freezing wind, or traffic chaos.
Hundreds of hours are spent drawing lines on laminated maps of the city, working out the most direct route from hotel to station, restaurant to office, monument to square. We learn thousands of "points of interest", taking in around 25, streets. And we don't just sit an exam, we have a potentially endless series of "appearances", in which we recite the perfect route between any two points in the city, until the examiners think we're good enough.
I had 19 of them over a period of 18 months — many candidates have more. The terror of the appearance is legendary — ask any cabbie and watch him wince. In the "olden days", John Mason — head of taxi and private hire at TfL — tells me, the examiners would play games such as putting the chair in the examination room facing the wrong direction, and give an automatic fail to the student who dared turn it around.
He remembers one examiner who would choose the start and end points of his questions by throwing two darts into a map, and if the student felt this was unfair he would offer to let them throw the darts instead. Well, you can't deny the industry needs to modernise. And it is doing so. You may not have noticed, but the classic cab is being retired. With a career broadly parallel to the much-mourned Routemaster bus, the Austin FX4 was introduced in , updated and rebranded the Fairway in , and — owing to air-quality targets set by the mayor of London's office meaning that vehicles more than 15 years old will no longer be licensed — is set to all but disappear from the streets of the capital in the new year.
A handful have been granted extensions and will remain as a rare sight for a few months, but the Fairway has reached the end of the road. Meanwhile, hundreds of its successor — the bubblier TX drivers often refer to it as the "Noddy cab" — have been recalled with mechanical problems and, as you may have read, its manufacturer Manganese Bronze has gone into administration.
Mercedes already licensed and Nissan probably due in are offering fuel-efficient people carrier style alternatives that appeal to the cost-conscious driver. For those of us who care what the London taxi looks like , these are worrying times, although Mason assures me TfL is consulting with other manufacturers with the hope of finding a distinctive London equivalent. But it's not just the vehicles that are changing.
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