The extraordinary brain of taxi drivers: what science discovered

The brain of taxi drivers became famous thanks to a series of studies by University College London on London taxi drivers. The first, published in 2000 by neuroscientist Eleanor Maguire's team, found that the rear part of the hippocampus, a key region for spatial navigation, was larger in taxi drivers than in people who did not drive taxis, and the more so the more years they had been in the job. It became one of the most cited pieces of evidence that the adult brain changes with learning.

The hippocampus is a structure located in the inner part of the temporal lobe, one in each hemisphere. It is involved in forming memories and in spatial memory: it is what allows us to build a “mental map” of a place and know how to get from one point to another. For a long time it was thought that the structure of the adult brain barely changed; taxi drivers helped to qualify that idea.

To drive one of London's black cabs you have to pass “The Knowledge”, an exam famous for its difficulty that requires memorising thousands of streets and places in the city centre and being able to plot from memory the route between any two points. Preparing for it takes years. That made London cabbies an ideal group for studying what happens in the brain when someone learns a huge map and uses it every day.

Later studies refined the conclusions:

• It was not a pre-existing difference. By following trainees before and after preparing for the exam, researchers saw that the increase in the rear hippocampus appeared in those who passed, and not in those who dropped out or in the comparison group.
• It does not depend on driving, but on navigating. Compared with bus drivers, who repeat fixed routes, only taxi drivers showed the difference.
• There are trade-offs. The front part of the hippocampus turned out to be somewhat smaller in taxi drivers, and they performed worse on some tests of new visual memory. The brain seems to reorganise itself, not simply “grow”.

The taxi driver studies opened a debate that is still going on: whether following satnav directions makes us use our spatial memory less. Some researchers argue that planning the route yourself involves the hippocampus more than obeying step-by-step instructions. Day to day, most taxi drivers combine both, as we explain in between GPS and a taxi driver's sense of direction.

Madrid does not have an exam as legendary as London's, but knowledge of the city is a central part of the municipal exam for obtaining a taxi driver's permit, along with the regulations and fares. We explain it in requirements for working as a taxi driver. After that, it is the years behind the wheel that turn that syllabus into something like a living map, the taxi driver's wisdom that passengers value so much.

That sense of direction is especially noticeable on airport journeys, when the best approach to the terminal has to be chosen according to the time and traffic. If you have a flight, you can book your taxi at a fixed price (€33 from inside the M-30; the other areas on our fares page) or order it easily on WhatsApp.