Mary Laur, an editor for The Chicago Manual of Style, says part of her job is fielding the inevitable questions. Just like anyone who works in IT is charged with fixing his mother’s wireless router (Hi Mom!), she gets asked to settle her friends’ grammar and usage disputes. Her most popular challenge: is it one space after a period at the end of a sentence, or two?

The Manual’s answer to this question is simple enough—one—but I have learned from experience that everyone who asks it wants me to say two. Often I suspect they know my answer in advance and hope to pick a fight with me. Even before I became part of the Manual revision team, I once had exactly this argument with my graduate advisor, who eventually relented and accepted my master’s thesis minus the extra spacing. Now, I am just old enough to understand that anyone who took a high school typing course through the 1980s internalized “period-space-space” through countless hours of practice drills, and to many of these people, “period-space” just looks wrong.

I learned to type on a typewriter in the 90s, so two spaces are hardwired into my muscle memory too. I’ve known for some time that one space is now proper usage, but relaying that from my brain to my fingers as I type is next to impossible. Laur points out that computer fonts generally correct for this anyway. Using Twitter may help me overcome the two-space habit though, because when every character is precious I make sure to conserve space.