If modern London was ancient Athens, London taxi drivers would be worshipped as the Gods of Navigation, appeased only with offerings of fluffy dice and pine-scented air fresheners.
Because, before being able to drive one of the legendary black cabs, a wannabe taxi driver must pass a gruelling trial known as ‘The Knowledge’. This consists of memorising 320 routes along London’s 25,000 streets, as well as all nearby landmarks and places of interest.
Drivers train for up to four years before taking the test, racing around the capital on a scooter until every last route has been committed to memory. This wouldn’t be such a difficult task in a place like New York City, where the roads are numbered and gridded, but on London’s gloriously haphazard streets it’s an undertaking of epic proportions.
Spot the difference: a snapshot of the New York City (left) and London (right) street layouts (credit: Google Maps)
This navigational know-how has made London taxi drivers surprisingly popular with neuroscientists, who have long wondered how cabbies retain so much detailed information. Around ten years ago, Eleanor Maguire and colleagues at University College London discovered that part of the hippocampus, a structure in the brain associated with memory and navigation, is larger in taxi drivers, and that this region grows with taxi driving experience. Their conclusion: the information acquired during The Knowledge physically changes a cabbie’s brain!
But there’s an alternative way to interpret this result: what if the cabbies’ hippocampus differences were already there before The Knowledge? Maybe people with these brain structure peculiarities naturally have better navigational skills and are therefore more likely to become taxi drivers? To test this, Maguire and colleagues looked for a relationship between navigational skill and hippocampus size in people with no taxi training. The researchers failed to find a link, confirming that the taxi drivers’ brain differences are due to The Knowledge, rather than to any innate, pre-existing navigational talent.
A mini minicab (credit: lmg123)
This is all very exciting for neuroscientists because it means that the brain can exhibit ‘plastic’ behaviour, changing its grey matter volume in response to environmental stimulation. The process even works backwards: a study of retired cabbies found that the brain’s structural changes start to reverse once The Knowledge stops being used (“use it or lose it”).
This plastic ability of the brain could be important for people with brain injuries or diseases such as Parkinson’s. If, as these studies suggest, stimulating a brain can change its structure, it may be that brain injury patients can be rehabilitated using a similar method.
A London cabbie...he's probably got a bigger hippocampus than you (credit: silvertony45)
Meanwhile, a follow-up study has found that taxi drivers aren’t completely infallible. Katya Woollett, a researcher at London’s Institute of Cognitive Neuroscience, has tested the ability of cabbies to find their way around a simulation of London which incorporates a new, made-up district. Surprisingly, taxi drivers fared worse at navigating around this ‘new London’ than people without any navigational expertise.
This may be because the modified city is too similar to the taxi drivers’ memorised street maps, making it difficult for a cabbie to change his route-finding habits. Some drivers also recalled experiencing similar problems when the Canary Wharf district opened in the 1990s.
So this proves that not even London cabbies are perfect navigators – a small nugget of hope, maybe, for those of us who’d fail to find our way out of a paper bag.
Maguire, E. (2000). Navigation-related structural change in the hippocampi of taxi drivers Proceedings of the National Academy of Sciences, 97 (8), 4398-4403 DOI: 10.1073/pnas.070039597
Maguire, E., Spiers, H., et al. (2003). Navigation expertise and the human hippocampus: A structural brain imaging analysis Hippocampus, 13 (2), 250-259 DOI: 10.1002/hipo.10087
Woollett, K., & Maguire, E. (2010). The effect of navigational expertise on wayfinding in new environments Journal of Environmental Psychology, 30 (4), 565-573 DOI: 10.1016/j.jenvp.2010.03.003