“A key fact about such mental representations is that they are very “domain specific,” that is, they apply only to the skill for which they were developed. We saw this with Steve Faloon: the mental representations he had devised to remember strings of digits did nothing to improve his memory for strings of letters. Similarly, a chess player’s mental representations will give him or her no advantage over others in tests involving general visuospatial abilities, and a diver’s mental representations will be useless for basketball. This explains a crucial fact about expert performance in general: there is no such thing as developing a general skill. You don’t train your memory; you train your memory for strings of digits or for collections of words or for people’s faces. You don’t train to become an athlete; you train to become a gymnast or a sprinter or a marathoner”