The scientific case for two spaces after a period

‘The Atlantic’ has a report on a study about this vexing subject while driving home the point that the study must consider other factors such as comprehension and the usage of mono-spaced fonts

One thing that apparently still has the power to infuriate people, though, is how many spaces should be used after a period at the end of an English sentence.

The war is alive again of late because a study that came out this month from Skidmore College. The study is, somehow, the first to look specifically at this question. It is titled: “Are Two Spaces Better Than One? The Effect of Spacing Following Periods and Commas During Reading.”

It appears in the current issue of the journal Attention, Perception, and Psychophysics. As best I can tell, psychophysics is a word; the Rochester Institute of Technology defines it as the “study of the relationship between stimuli (specified in physical terms) and the sensations and perceptions evoked by these stimuli.” The researchers are also real. Rebecca Johnson, an associate professor in Skidmore’s department of psychology, led the team. Her expertise is in the cognitive processes underlying reading. As Johnson told me, “Our data suggest that all readers benefit from having two spaces after periods.”

“Increased spacing has been shown to help facilitate processing in a number of other reading studies,” Johnson explained to me by email, using two spaces after each period. “Removing the spaces between words altogether drastically hurts our ability to read fluently, and increasing the amount of space between words helps us process the text.”

In the Skidmore study, among people who write with two spaces after periods—“two-spacers”—there was an increase in reading speed of 3 percent when reading text with two spaces following periods, as compared to one. This is, Johnson points out, an average of nine additional words per minute above their performance “under the one-space conditions.”

Read the full report here.

(Photograph: Tina Fineberg / AP/The Atlantic)

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