I love this! I recently asked myself this question, lol.
When you are limited to 5 pages, every space in your brief counts. Save the trees!! 
Given the detail provided in the article - one font used, reading only improved for those study subjects only using 2 spaces already - let alone a pretty small number of test subjects, I’d call it inconclusive. And a waste of $ and time.
About a decade ago, I worked for a government contractor with three clients. All our work for agencies A and B had to have single spaces after periods. But all the work we submitted to agency C had to have double spaces. It drove me nuts.
This is not the reason why I left that job, but it could have been.
I type really fast and pretty much without thinking. My muscle memory is two spaces.
I was raised on two spaces and still use them unless i am constrained by character limitations. S17 gets hysterical if his papers are typed with 2, he says it has to be one! I used to type his papers for him before he got voice recognition software.
“Wrong” might be too strong a word.
The generation currently in school has been taught, rightly or wrongly, to only use one space after a period. The Chicago Manual of Style. the AP Stylebook, and The MLA Style Manual all recommend one space after a period. Note that my use of serial commas in the prior sentence is also a subject of debate amongst the various guides.
In the past, before the magma cooled and dinosaurs roamed the earth, kids were also taught in something called penmanship class (whatever that was 
) to make an upper case Q look like a 2. I’d posit there are few people of any age who follow those guidelines today when using cursive. Life evolves.
It took me about 2 years to break the 2 space training. Habits are tough to change. Now I am so used to one space that two looks like a mistake.
Who even uses 2 spaces anymore? I was surprised that 1/3 of the study participants used two spaces, given they were college kids IIRC. I’d only expect that from people who originally learned on typewriters. I do also think using a fixed-width font very likely affected the results. I only see (and personally use) fixed-width fonts for computer code, with variable-width fonts for everything else.
The Q looking like a 2 reminded me of the time I had hand-written something and D commented “I wish I could write like that”. I had written in cursive and D only prints. Kids these days…
I only print and I have crappy penmanship. Speaking of handwriting, mine has always been lousy but it has gotten SO much worse out of lack of practice. I’m busy hand-writing some thank you notes for donations to a group I’m active with and it is so painful and I worry about how illegible they are. I have to take a break after each one because they get even more illegible if I don’t. I’ve lost what little muscle memory I had. Am I the only one that has this problem?
I’ve so ingrained into my two millennials, that they agree that two spaces looks better and reads faster. However, in the Style Manuals for the respective industries say just one space and they hate it. hahahahaha
Yea, my penmanship is pretty lousy from lack of use as well. Back in law school I used to be able to take verbatim notes of everything the profs said during class—don’t believe I could do that any more except if I were typing on a keyboard.
My penmanship was never great to begin with but sadly has worsened. I must say learning typing in middle school was very useful. I typed the papers for me and my mom and siblings until I went off to college and left them to fend for themselves.
It was always my understanding that computers and word processing software are what changed the spacing issue. I remember using the early Macs and the thing was that it automatically put a bit of extra space after a period so there was no need to use the space bar twice. I have worked as a journalist and copywriter for over 20 years. The only time I have ever spacebared twice was during typing class (on typewriters) in high school (late 80s).
I will concede one place where one space is better — Twitter. I’ve often gone back and taken out my customary 2nd space to gain a couple more characters for a Tweet. And I admit, my resume and cover letters as well. Just in case there is a (silly) judgemental millennial on the other end. But 2 is still my standard.
I indeed was one of those taught the “2” Q in penmanship, @skieurope. But I knew it was dumb the day they showed it to me at age 7. And hey — look at Hawaii today, the magma still flows. And 2 spaces rises again. Long live the dinosaurs!
P.S. - Jusr saw that author Laurie R. King is celebrating this article today — good enough for her & Inspector Gamache, good enough for me!
P.P.S. - I wonder if this became a computer standard to save on storage costs. Some programmer didn’t want to store 2 bytes when they thought one would do. Storage was expensive in the early days. Could be the real reason this was pushed to start with.
LOL. I’m a two-spacer and kids are one-spacers. Dfferent protocols were in place when we learned when we started to type.
I have a hard time with single space between sentences. Old habits from typing are tough to extinguish.
Doesn’t CC omit the second space? Testing here. Yup- they got rid of it. It shows up when I edit but then reverts to their correction. Wonder if that two spacing rule helped more with handwritten pieces since they can be harder to read and less regular spacing.
That’s not CC; that’s your browser.
The browser rules the computer then. CC does enough choosing that I can’t modify.