Building The Knowledge

London Taxi Photo: David Iliff, License: CC-BY-SA 3.0

The classic source of information for a newcomer in any major city was the taxi driver. Usually they knew their city in detail and would drive you around the important features, (for a fee of course,) while educating you in the politics and the comings and goings of the important and beautiful people of the place. Now the GPS has replaced that detailed mental map and you get more politics and gossip than education.

London, though, is hanging on to tradition. GPS units are not for the London cabbie who needs to find short cuts to dodge the usual traffic jams. The cabbie’s job needs more brain than can be found in a little box of electronics. Flexibility and instant decisions are required in addition to the map.

To get a Hackney Cab License in the City of London, a potential cab driver has to study hard to acquire “The Knowledge”. It can take about four years to pack the details of 320 routes around Charing Cross into one's brain. Details, details and more details have to be instantly recalled. How many of us could instantly recall any one of 25,000 different streets let alone not fail to mention one of 20,000 landmarks when asked.

That’s a lot of “Knowledge” to stuff into anyone’s head and Woollett and Maguire of U College have followed the stuffing process with 79 prospective London cabbies. Of course, the big magnet was rolled out and fMRI scans were done over the four-year training period (along with controls of course).

Some of the candidates showed increasing gray matter building up in the front part of their brains, their posterior hippocampi to be exact.  These guys passed the test and got their licenses. The ones whose brains didn’t change failed and are now going by bus.

It is interesting to note that their heads didn’t get bigger to accommodate the fresh gray matter. It appears that the failing potential cabbies were able to do better on complex visual memory tasks than the passing ones. So it seems that the spatial memory required for  “The Knowledge” takes up a lot of space and crowds out other functions. All part of the price for getting a license to drive the rich and famous as well as you or I, I suppose. 
  2. K. Woollett & E.A.Maguire, J. Curr. Biol, (2011), doi: 10.1016/j.cub.2011.11.018

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