Can your brain change? How much is it actually affected in structure by your daily life? Does it adapt to suit your individual needs? These were all questions that Maguire wanted to answer when she carried out her well-known taxi-driver study.
To test this, she needed to find a group of participants with an extreme area of expertise about a subject and compare their brains, to the brains of ‘normal’ people. There is a well-known area of the brain called the hippocampus, and this area is known to be used for spatial memory. It is how we remember routes to and from work or school and go about our daily lives without getting lost every two seconds. Maguire felt that the spatial memory of London taxi-drivers naturally had to be stronger than that of anyone else. I should explain that London taxi-drivers must take a test known by some as simply ‘The Knowledge’, before they are allowed to drive a registered London taxi. This can test them on any of the locations and routes in London and so all taxi drivers must have a comprehensive knowledge of every street and venue in London. Because of this, it makes sense that they would have a greater spatial memory than most people.
Maguire took 16 healthy male taxi drivers who had all passed ‘The Knowledge’ and gave each an MRI (Magnetic Resonance Imaging) Scan. She then did the same with 50 healthy males from other professions. From the MRI scans, the pixels of grey matter and white matter in the hippocampi were calculated and the density of the neurons in these areas was also measured. It was found that the taxi drivers had significantly larger posterior hippocampi, while the anterior hippocampi were relatively smaller than the ‘normal’ group. It was also found that the amount of difference in these two areas from the ‘normal’ brain was related to the length of time spent as a taxi driver.
The first finding shows that due to the demands of the profession the brain was able to change to suit its environment. This adaptation to suit an individual’s needs is now known as neuroplasticity. The posterior (back part of the) hippocampi, which were larger for taxi drivers is used for storing spatial memories, which makes sense, since taxi drivers have a large database of locations across London stored in their brain. On the other hand, the anterior (front part of the) hippocampi were smaller, and this is the part that is related to making new spatial memories, suggesting that while taxi-drivers have a greater storage capacity for spatial memories than the majority of us, their ability to improve this memory further is reduced. This therefore makes it likely that there is a limit to spatial memory, which will be reached when people completely lose the ability of their anterior hippocampus to make new spatial memories. Therefore, interestingly, though the mind can change as we improve at one particular activity, this will generally result in a compromise, whereby ability at another activity is reduced, since when one brain area increases, it must use up space from another brain area. The second finding shows that the longer we have been working on a skill for, the stronger our brain becomes at dealing with it. With this in mind, it may be best to choose what it is we want to get good at early in life, so that our brains have the greatest chance of adapting to suit these skills and specialising themselves for them.
Image from: http://247swindontaxis.co.uk/images/fullscreen/v05.jpg
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