The 2006 finding of increased grey matter volume in the posterior hippocampus in London taxi drivers who have had to learn ‘The Knowledge’ is well known. Mark Twain addressed a similar subject phenomenologically in his 1883 book Life on the Mississippi.

Samuel Clemens took his pen name from the cry on a paddle steamer meaning ‘Safe water! Go ahead!’ He earned his right to it from the 5 years he spent in his 20s as a pilot on the Mississippi steamboats. These pilots faced a considerable challenge: ‘Ol’ Man River’ was a vast and unpredictable waterway whose muddy banks were constantly shifting, creating and then swallowing islands reefs and sandbanks, generating new currents, eddies, channels and treacherous shallows. To his dismay, Twain was told by his mentor Mr Bixby that he would have to ‘learn the shape of the river in all the different ways which could be thought of – upside down, wrong end first, inside out, fore-and-aft, and thortships – and then know what to do on gray nights when it hadn't any shape at all.’

Twain developed a deep admiration for his fellow navigators, saying of a pilot that his ‘movements were entirely free; he consulted no one, he received commands from nobody, he promptly resented even the merest suggestions. Indeed, the law of the United States forbade him to listen to commands or suggestions’. The main reason for this high status was the ‘faculty which a pilot must incessantly cultivate until he has brought it to absolute perfection. Nothing short of perfection will do. That faculty is memory.’

Twain describes the pilots' ability to be guided by their memory in the face of all distraction, as well as the highly focused nature of their superior retentive faculty, so that they might read the river exactly – but not recall what they'd had for breakfast. He also mentions one pilot whose prodigious memory was global in its capacity, but with the disadvantage that he could not forget anything, so he was constantly distracted. He might start telling a funny story about a dog but then veer off into references to owners, their families, the prices of fodder and livestock, circuses, Africa, religion and the power of prayer; mentioning nothing more about the dog.

In time, the pilots established a closed shop, the Pilots’ Benevolent Association, which added an important supplement to the powers of their memories. This involved a system of locked boxes that were kept at all main stopping points on the river and which could only be opened with special keys held by Association pilots, providing a means whereby information could be securely shared. This improved safety on the river so much that the pilots' monopoly was enforced by ‘a power behind the throne that was greater than the throne itself. It was the underwriters!’

Thus, the best results came from cooperation added to the power of individual memory. Where does the best balance lie today between using our trained memories and outsourcing the task to search engines and mobile devices?