According to “Reading in the Brain,” we assemble words in alphabetic writing systems by grouping sets of 3 letters in each 5 (IIRC). To read the word BRAIN, we assemble BRA, RAI, AIN, BRI, RAN, RIN etc., and map to which words best match those triplets. That’s why it’s so easy to mix up BRAIN and BRIAN – they’re not just the same letters in almost the same order, they’re almost the same triplets.
I imagine that’s also why I consistently misread “NSW” as “NSFW” instead of “New South Wales.”