Chess players’ memory skills seem related to expert sight reading abilities.
Research on chess players’ memory showed that experts had a profound ability to remember positions of chess pieces on a chess board – no surprise! But what might be a surprise is that this aptitude disappeared if the chess pieces were placed in orders not possible in chess. If the placement were totally random, chess experts’ memories were roughly comparable to an average non-chess player. The theory goes that chess players are “reading” the board differently based on all of their past chess experiences, but if the position couldn’t be played into, it didn’t make sense.
You can imagine the same situation with professional actors; they might be able to process and memorize dialogue faster than you or me, but they wouldn’t be able to memorize random strings of letters much better.
I think this sort of domain-specific chunking of information is what makes expert sight readers so good. All their past reading experiences enable them to recognize larger patterns in the music at a subconscious or unconscious level. They’re not playing individual notes but phrases, based on every other pieces they’ve ever played. If you put a piece in front of a brilliant sight reader that didn’t conform to basic music conventions of notation, harmony, melody, etc. they would likely be roughly similar to a young musician just learning to sight read.
The trick to get better at sight reading, then, is to build your domain knowledge by reading a lot. No shortcuts.