My mind, seeing the word, and knowing what it was supposed to be, did not even register it as a misspelled word. Why is this you ask?
I live in a family of atrocious spellers. After so many years of struggling through their writings, my mind has conditioned itself with auto spell check. This makes it interesting when Hubby asks me to proof his papers for work or school. I have to manually disengage the mind spell checker and slow my reading WAY down to catch anything that may be used or spelled incorrectly. I've learned his most frequent error (using than instead of then) and first browse the paper looking for that. I then go through it with a fine tooth comb and look for any other incidents. I have found the easiest way to do this is to read it backwards. I start with the last word on the page, and read from bottom to top, right to left. A bit cumbersome, but I haven't missed anything yet!
Hubby has actually improved dramatically since we were first married. I (literally) forced him to start reading books (he never really read for fun before) and his spelling has improved significally. I decided to avoid all this with my kids. Starting from an early age, they have been exposed to books and encouraged to read. My twins now love to read to the point that they sometimes can't put the book down and end up getting in trouble for not paying attention in school. My 9 year old is a budding reader, but is still easily distracted by shiny objects. I think he has potential though!