Why we are blind to our own typos

Here is an interesting article by Nick Stockton explaining why it’s so hard to catch our own typos. He ends with a hint that most of us already know: when proofreading, print a hard copy and edit by hand.

One of my own tricks when doing that is to use a ruler, placing it just under the line of text I’m examining. Every time I do that, I catch about a half-dozen typos and other mistakes.