“Professionals and amateurs in a variety of fields have passionately argued for either one or two spaces following this punctuation mark,” they wrote in a paper published last week in the journal Attention, Perception, & Psychophysics.
They cite dozens of theories and previous research, arguing for one space or two. A 2005 study that found two spaces reduced lateral interference in the eye and helped reading. A 2015 study that found the opposite. A 1998 experiment that suggested it didn't matter.
“However,” they wrote, “to date, there has been no direct empirical evidence in support of these claims, nor in favor of the one-space convention.”
I love that the permalink for this article has a trailing 2, which indicates to me that it took the editors a second attempt to add the additional space into the headline for their CMS. And if nothing else, this article is interesting for its layout and typesetting.
I’ll circle back to read the full journal article shortly.1