Should you use one or two spaces after a period?

You sit down to compose an email. You write one sentence, and appropriately end it with a period. What happens next is, apparently, a subject of hot debate.

Do you put one or two spaces after the period before starting your next sentence? People belong to one camp or the other, and both camps are very passionate about their stances.

It turns out that whether you use one space or two may depend upon your age. People began inserting two spaces after the period during the era of the typewriter. When typing on a typewriter, each character took up the same amount of space on the page. Having an extra space after the period was helpful in delineating the start of a new sentence.

With the days of typewriters long gone, however, that logic no longer applies. Still, some people are standing by their assertion that two spaces is preferable. Take Yale sociologist Nicholas A. Christakis, for example. He recently tweeted that his habit of using two spaces has been “vindicated by science”:

Christakis shared a link to a study that analyzed the effect of spacing following periods on reading comprehension.

“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,” the researchers wrote.

I, personally, believe that one space is the way to go. I’ve always bristled upon seeing two spaces. But really, the consensus on whether you should use one or two spaces depends upon who you ask (which sort of means that there’s no consensus).

According to the aforementioned American Psychological Association (APA), two spaces is preferred. According to the Modern Language Association (MLA) Style Center, on the other hand, a guide commonly used in academic settings, one space is appropriate, “unless your instructor prefers two spaces.” The Associated Press (AP) Stylebook, which journalists adhere to, calls for a single space.

What do you think? Do you have a spacing preference?