Google “tact filter” and you’ll come to a a page at MIT that was originally posted in 1996. It’s a metaphor — and a very useful one — for the differences between the way “normal folks” apply tact and the way “nerds” apply tact.

Most folks edit before they say something, to minimize the chances of hurting someone’s feelings. Nerds expect and respect blunt and frank discussion instead, and they edit what they hear as it comes in.

So most folks edit before transmitting, and nerds edit after receiving. Pretty neat idea.