To me this is exactly analogous to other tricks the brain plays on us - where the brain fills in the gaps because that's what brains do - fill in the gaps, put things in order, add structure to apparent chaos.
Absolutely; most of us seem to be hard-wired to try to find a pattern, and preferably a familiar one.

I had no trouble reading the letter (Hello, sweet paulb, and thanks!); but, as the link to S.D.* shows, the longer the word, the harder it gets. (Unless it's clear from the context what the word ought to be, I start having to pause at words of about 8 letters.) Out of context could be hard indeed. I have found this true in many kinds of word puzzles, where you have to pick a word out of thin air, and try all kinds of permutations to find out whether you got the right one or not.

Keith, your statement about crosswords intrigues me. Does anyone have any experience with crossword puzzles in other languages?

*It always hurts my feelings to find out that a topic here has already been discussed elsewhere. I believe this group to be the best and the brightest (not that I'm prejudiced or anything!), and I also want us to be first!