 A study was carried out on taxi drivers.London’s black cab drivers need to learn the locations of a large number of places and the fastest routes between them in order to pass a strict test known as The Knowledge in order to gain a license to operate.A study showed that the posterior part of the hippocampus is larger in these drivers than in the general public, and that a positive correlation exists between the length of time served as a driver and the increase in the volume of this part.