After my recent post about putting only one space (not two) between sentences, a friend pointed out a recent article in Attention, Perception & Psychophysics. According to the article, the authors (Rebecca L. Johnson, Becky Bui, and Lindsay L. Schmitt) did a study about this subject. Here’s the abstract:
The most recent edition of the American Psychological Association (APA) Manual states that two spaces should follow the punctuation at the end of a sentence. This is in contrast to the one-space requirement from previous editions. However, to date, there has been no empirical support for either convention. In the current study, participants performed (1) a typing task to assess spacing usage and (2) an eye-tracking experiment to assess the effect that punctuation spacing has on reading performance. Although comprehension was not affected by punctuation spacing, the eye movement record suggested that initial processing of the text was facilitated when periods were followed by two spaces, supporting the change made to the APA Manual. Individuals' typing usage also influenced these effects such that those who use two spaces following a period showed the greatest overall facilitation from reading with two spaces.
Unfortunately, to read the article itself, you have to shell out $39.95, which I wasn’t willing to do. (You can buy Matthew Butterick’s Typography for Lawyers for only $30.) Fortunately, I found this blog post in Lifehacker, where Nick Douglas did the homework.
Long story short: The font that Johnson et al. chose for their study was Courier New, a monospaced font that replicates a manual Underwood typewriter. The two-space convention is a vestige of the typewriter days, when everything was monospaced. This news just in: no one outside of prison writes a brief or any other court document on a manual typewriter using a monospaced font. For a few decades now, we’ve all had computers, and our documents have been written in proportionally spaced fonts. So as I said, “Unless you’re banging out your briefs on an Underwood manual typewriter, put only one space—not two—between the end of one sentence and the first letter of the next sentence.”
One more absolute rule for typography: No underlining. That will be the topic of a future post.