London Hackney

My wife and I love the CBC television reality show, The Amazing Race.  We routinely binge watch some of the seasons we've missed (actually, we haven't missed too many).  During Season 31, the contestants who made it to the 11th leg of the race in London, England experienced the "Detour" ("a choice between two tasks, each with its pros and cons"), "Know or Row."  In "Know" contestants had to ride in one of the famous London black taxicabs ("hackneys") and memorize fifteen streets and seven landmarks that their taxi driver pointed out to them during the ride. At the end of the ride, contestants had to correctly recite their route to another cab driver in order to receive their next clue.  It sounded very hard (the other option "Row" was more physical in nature).

Apparently, the test that prospective London cab drivers have to pass to obtain a license is one of the most difficult tests in the world!  Basically, the cab drivers have to memorize a detailed map of the city of London and pass a series of progressively more difficult oral examinations before they are allowed to drive a taxi cab.  The entire process can take up to four years, and in many cases prospective cab drivers spend even longer.  Some experts have quipped that it might be easier to pass a test to become a lawyer or physician!  

The guidebook issued to prospective cab drivers by the London Taxi and Private Hire (LTPH), which oversees the test, summarizes the requirements as follows:

To achieve the required standard to be licensed as an “All London” taxi driver you will need a thorough knowledge, primarily, of the area within a six-mile radius of Charing Cross. You will need to know: all the streets; housing estates; parks and open spaces; government offices and departments; financial and commercial centres; diplomatic premises; town halls; registry offices; hospitals; places of worship; sports stadiums and leisure centres; airline offices; stations; hotels; clubs; theatres; cinemas; museums; art galleries; schools; colleges and universities; police stations and headquarters buildings; civil, criminal and coroner’s courts; prisons; and places of interest to tourists. In fact, anywhere a taxi passenger might ask to be taken.

Notably, the six-mile radius of Charing Cross "only" contains 25,000 streets, and cab drivers have to know which ones are one-way and which ones are not.  They also have to know what's the best way to get on or off a particular street, in addition to everything on these streets.  One cab driver reported that he was asked to locate a rather obscure statue of two mice eating a piece of cheese - the statue was only 1 foot tall!

For more than a century, the test has been known as "The Knowledge of London" or simply, "The Knowledge."  The Season 31 Amazing Race Detour "Know" gave contestants and television viewers just a glimpse of the test.  "The Knowledge" is testament to the incredible capacity of the human brain to acquire and store a vast amount of information.  Here is where things get really cool!  Apparently, the volume of the hippocampus (a structure located deep within the brain's temporal lobe that plays a major role in learning and memory) relative to the body size of small mammals (mice, rats, and birds have been studied in particular) varies based on the demands placed on spatial memory (even from year to year).  So, for example, during seasons when animals need to remember how to go back to the place that they stored food, the volume of the hippocampus will increase (the volume of the brain meets the demands placed on it).

The natural question is (1) whether the hippocampus of individuals who pass "The Knowlege" is larger than those who haven't passed it and (2) whether the hippocampus increases in size as individuals study and prepare to pass "The Knowledge."  Cognitive neuroscientist Eleanor Maquire and her team have published a number of studies using advanced magnetic resonance imaging (MRI) and positron emission topography (PET) techniques to answer these questions.  These studies can be summarized by the following key points:

1. The right hippocampus of the brain is most active (shown with PET) during spatial memory tasks (London taxi cab drivers asked to recall famous London landmarks and/or street directions).

2. Structural MRI shows that the posterior hippocampus is larger in volume in London taxi cab drivers compared to control subjects (moreover, the gray matter volume of the posterior hippocampus correlates directly with the number of years spent as a taxi cab driver).

3. Structural MRI shows that the posterior hippocampus is larger in volume in London taxi cab drivers compared to London bus drivers.

4. The gray matter volume of the posterior hippocampus increases over time as London taxi cab drivers study for "The Knowledge" from start to finish.

Collectively, these studies illustrate the remarkable ability of the brain to adapt to the demands of its environment over time (called plasticity in the neuroscience literature).  What's the take-home message here, you ask?  First, no matter what age we are, our brains can continue to develop with practice and experience.  Second, if we want to get better at something - even learning how to navigate the city streets of London, but more relevant, perhaps leading others - we have to practice!