It takes 3-4 years to become a licensed London taxi cab driver, because the test is so hard. Those are years spent studying for a comprehensive test of the London map. A new study in Current Biology, by Katherine Woollett and Eleanor Maguire, shows that that studying for this test changes the structure of the drivers' brains. Along with other similar findings, this study shows the brain remains plastic and adaptable into adulthood.
Seventy-nine taxi-drivers and 31 non-taxi drivers signed up for the study. Their brains were scanned when they began studying for the test and again 3-4 years later after they took the test. Studying for the test enlarged the posterior hippocampus--an area of the brain associated with spatial memory—but only in those trainees who passed the test. Similar enlargement did not occur in drivers who did not pass the test, nor in the control (non-taxi driver) group.
This finding is similar to a previous study of London taxi drivers. The previous study suffered from a chicken-and-egg problem: It wasn't clear whether driving increased hippocampal volume or whether large hippocampal volume made people talented taxi drivers. Because the new study followed people over time, and identifies the training as the cause, and the changed brain structure as the effect.
The brain stores the information we learn. New information cannot be encoded without a change in the state of the brain. Thus, whenever we learn something it changes our brains. But these changes are usually small changes in connections between neurons. They can be thought of as functional changes.
The taxi driver study is remarkable because it involved structural changes, not merely functional changes. A functional change in the brain is similar to storing a new file on your computer. A structural change is like buying a new computer--or at the very least, swapping out your RAM or getting a new motherboard. It's a hardware change.
Spatial memory is a pervasive force in our lives, and has been for eons. Our ancestors felt enormous evolutionary pressure to remember what they had experienced in a certain location (did I find a rich food source or did I almost become one?). Just ask a bee out foraging for nectar or a lion maintaining its territory.
Spatial memory separates some species from others. For example, there are birds that hide thousands of nuts during the fall, before the snow falls, and are able to retrieve the nuts, months later, after the world has been blanketed with white. These birds aren't geniuses in all aspects of life, to be sure, but their spatial memories are better than mine. (This is one of the most telling examples of the modular nature of intelligence. Species have different abilities, and a species can be smart at one thing and not so smart at another, just like a person. Which is why I grow suspicious when people say an ape is as smart as a 3 year old child. Specific abilities can be compared, but an entire species should not.)
Spatial memory also separates people from each other. Taxi drivers are amazing. I, on the other hand, cannot find my way around the town I grew up in. And when I walk out of an elevator, I always think I'm still facing the way I was facing when I walked in. (Is it just me?) I guess I need a bigger posterior hippocampus. Maybe I should start studying maps.
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