An inconclusive psycholinguistic take on post-period spacing
A while back, I peeved about the people for whom public devotion to single-spacing after a period is a form of virtue-signaling. I’ve now learned that the one-space-or-two issue has found its way into the journal Attention, Perception, and Psychophysics, which has posted “Are two spaces better than one? The effect of spacing following periods and commas during reading” ($) by Rebecca Johnson, Becky Bui, and Lindsay Schmitt.
The paper came to my attention via Matthew Butterick, the author of Typography for Lawyers and the free, online-only Butterick’s Practical Typography ("Are two spaces better than one? A response to new research"). He writes:
Apparently defying Betteridge’s Law, the study claims to show that two spaces after a period are easier to read than one. On its face, this also seems to contradict my longstanding advice to put only one space between sentences.
Because the study costs $39.95 for a PDF, I’m certain the social-media skeptics rushing to claim victory for two-spacing have neither bought it nor read it. But I did both.
True, the researchers found that putting two spaces after a period delivered a “small” but “statistically … detectable” improvement in reading speed—about 3%—but curiously, only for those readers who already type with two spaces. For habitual one-spacers, there was no benefit at all.
Furthermore, the researchers only tested samples of a monospaced font on screen …. They didn’t test proportional fonts, which they acknowledge are far more common. Nor did they test the effect of two-spacing on the printed page. The authors concede that any of these test-design choices could’ve affected their findings.
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