I agree with historyishere. It's amazing how quickly the brain adapts and starts ignoring the "y"s all together and reading the words based on a weird pattern recognition system. It will quickly scan the word and find out if a y actually belongs there. If not it doesn't really replace the y's with t's, but recognises the word as if it was a word with blanks instead of one or two letters. It works much like some communications technology that completes commonly used words for you as your typing.
I must say that, sometimes, what occupies your attention is a little bit scary, a little bit crazy, but if it wasn't for this type of human curiosity and attention to detail we wouldn't have those wonderful creatures, entomologists.
Marco
