I’ve got­ten sev­eral re­quests to ad­dress a new re­search study called Are two spaces bet­ter than one? The ef­fect of spac­ing fol­low­ing pe­ri­ods and com­mas dur­ing read­ing, writ­ten by Re­becca John­son, Becky Bui, and Lind­say Schmitt.

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 (roughly as shown be­low). 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.

In sum—a small dif­fer­ence, lim­ited to a cer­tain cat­e­gory of test sub­jects, with nu­mer­ous caveats at­tached. Not much to see here, I’m afraid.

Of course, I ac­cept the study. Sci­ence is real! I have a few quib­bles, noted be­low. But over­all, it pro­vides an ex­am­ple of why leg­i­bil­ity re­search is of­ten not as use­ful to prac­tic­ing ty­pog­ra­phers as we might hope. Ty­pog­ra­phy is broad and deep, and re­search stud­ies can only test nar­row propositions.

Most of all, though I will read any fu­ture stud­ies on this topic that may emerge—bud­get per­mit­ting—I agree with the re­searchers’ clos­ing thought: “we should prob­a­bly be ar­gu­ing pas­sion­ately about things that are more important.”

An ide­al­is­tic thought, but ar­gu­ing pas­sion­ately about dumb top­ics is the web’s rai­son d’être. In­ter­net ran­dos have been try­ing to rope me into ar­gu­ments about two-spac­ing for 10 years. I in­dulged them at the out­set. But not for a long time.

Why? Spoiler alert: I really don’t care how many spaces you put be­tween sen­tences. One? Two? Seven? π/4? Knock your­self out.

Ty­pog­ra­phy is not a sci­ence. Like lan­guage it­self, it has some struc­tural and prac­ti­cal con­ven­tions. If your goal is to per­suade read­ers, it’s wise to be aware of these con­ven­tions, be­cause re­ly­ing on them can help you. Con­versely, de­part­ing from these con­ven­tions may have un­in­tended consequences.

But in the end, it’s up to you. I’ve never held my­self out as the apex tastemaker nor the ty­pog­ra­phy po­lice. My project is to ed­u­cate writ­ers about these ty­po­graphic con­ven­tions, be­cause tra­di­tion­ally, these con­ven­tions aren’t taught along­side writ­ing. (Though they should be—in the dig­i­tal age, ty­po­graphic skill seems just as es­sen­tial as typ­ing skill.)

To that end, wher­ever there’s room for dis­cre­tion and choice, I say so. I want read­ers to de­velop their own ty­po­graphic judg­ment, not merely recre­ate mine, cargo-cult style. I de­ploy my sternest tone only for those ty­po­graphic con­ven­tions that are im­mov­ably en­trenched. In other words: let’s not waste en­ergy dis­put­ing the indisputable.

That’s why I start this book with one space be­tween sen­tences. Not be­cause it mat­ters much vi­su­ally. But rather be­cause the rule is so well set­tled. It’s a lit­mus test for ty­po­graphic skep­tics: if you can’t ac­cept that pro­fes­sional ty­pog­ra­phers al­ways use one space be­tween sen­tences, you’ll likely find the other rules a bore.

And some do. The cost of in­tro­duc­ing thou­sands to the plea­sures of good ty­pog­ra­phy is en­dur­ing a few heck­lers. I once gave a talk about ty­pog­ra­phy to a group of UCLA law pro­fes­sors. To­ward the end, one of them—known as the “em­pir­i­cal guy” on the fac­ulty—said “That’s all very in­ter­est­ing, Matthew, but why don’t ty­pog­ra­phers re­solve these mat­ters with em­pir­i­cal re­search? Surely it can’t be sub­jec­tive which font is best.”

“That’s a great idea, pro­fes­sor. By the way, have you re­searched what kind of law-re­view ar­ti­cle is most likely to get you tenure? How many words in the first sen­tence? Av­er­age num­ber of vow­els per paragraph?”

I didn’t say that; only thought it. Ob­vi­ously, it wasn’t a se­ri­ous ques­tion. This pro­fes­sor thought ty­pog­ra­phy was a silly topic, so he was dis­miss­ing it with the em­piri­cist’s ul­ti­mate put-down: you’re not be­ing em­pir­i­cal enough.

What I ac­tu­ally said to him went more like this—

Ty­pog­ra­phy—like lan­guage and every other form of hu­man ex­pres­sion—doesn’t oc­cupy a realm of strict ob­jec­tive truth.

That doesn’t mean ty­pog­ra­phers are hos­tile to the idea of re­search, or that leg­i­bil­ity can’t be tested. On the con­trary, many type­faces have emerged from forms of em­pir­i­cal re­search, for instance—

1. Retina was de­signed (orig­i­nally for the Wall Street Jour­nal) to stay leg­i­ble on low-qual­ity newsprint. Type de­signer To­bias Frere-Jones stud­ied how ink spreads on newsprint, and cut notches into the let­ter­forms to com­pen­sate. Though these “ink traps” look bizarre at large size, at small size they’re in­vis­i­ble. And in­stead of the let­ters look­ing blobby and gloppy, they just look correct.

   

2. The new font ap­proved for fed­eral high­way use, Clearview, de­signed by Don Meeker and James Mon­tal­bano. As a font for sig­nage, it had to be leg­i­ble for dri­vers at var­i­ous speeds and light lev­els, and was tested un­der these conditions.

3. Mi­crosoft’s Sitka font, de­signed by Matthew Carter, like­wise emerged from leg­i­bil­ity stud­ies about on-screen read­ing in Windows.

The ex­am­ples above share an im­por­tant fea­ture. In each case, the type de­signer was asked to op­ti­mize leg­i­bil­ity in a spe­cific read­ing con­text. There­fore, it was pos­si­ble to pose re­search ques­tions nar­row enough to be turned into testable propo­si­tions. (Not in­signif­i­cantly, these projects also had a cus­tomer at­tached who could pay for test­ing.) In turn, these tests pro­duced re­sults that were suf­fi­ciently pre­cise to be­come con­crete de­sign guid­ance. In sum, em­pir­i­cal re­search was use­ful specif­i­cally be­cause the prob­lem do­main was narrow.

Let’s re­turn to the law pro­fes­sor’s ques­tion: if we con­tin­ued this process, could we dis­cover the best font for every­thing? It looks hope­less. Re­search, by its na­ture, tests nar­row ques­tions. As I said in what is good ty­pog­ra­phy, ty­pog­ra­phy can’t be re­duced to a math prob­lem with one right an­swer. Like­wise, it’s dif­fi­cult to imag­ine a nar­row re­search ques­tion about fonts whose re­sults could be ex­trap­o­lated to every pos­si­ble context.

Still, even if em­pir­i­cal re­search can’t re­solve that many ty­po­graphic prob­lems, we needn’t de­clare ty­pog­ra­phy to be a do­main of pure whimsy. We can al­ways imag­ine ty­po­graphic so­lu­tions to a prob­lem that aren’t suit­able. In­deed, think­ing crit­i­cally about the in­tended read­ing con­text is al­ways help­ful “re­search” be­fore start­ing to de­sign a ty­po­graphic so­lu­tion. For in­stance, in pre­sen­ta­tions, I rec­om­mend turn­ing off the lights while work­ing on your slides, to bet­ter sim­u­late how your au­di­ence will see them. That’s not em­pir­i­cal. But as re­search, it’s bet­ter than nothing.

In that way, ty­pog­ra­phy func­tions much like writ­ten lan­guage it­self. We can—and should—use prag­matic con­sid­er­a­tions to nar­row down the space of pos­si­bil­i­ties. But when it’s time to choose from among those pos­si­bil­i­ties, there’s some art, hu­man­ity, and ex­pres­sive­ness to it. Just as no one can tell you the best open­ing sen­tence for your re­search pa­per, no one can tell you the best font for that pa­per, either.

Against that back­drop, if the main ques­tion we ask about a re­search study is what did it find?, the fol­low-up ques­tion ought to be what did it test?

First, let’s be clear about what this study didn’t test. Though the pa­per cites 48 sources—many psy­chol­o­gists, and a hand­ful of the afore­men­tioned in­ter­net crit­ics—it point­edly does not cite to any ty­pog­ra­phy au­thor­i­ties. Not me, not Erik Spiek­er­mann, not Robert Bringhurst, not Ellen Lup­ton, not Bryan Gar­ner, not the Chicago Man­ual of Style, not anyone.

But that seems right. Why? None of us are hold­ing out this rule as an em­pir­i­cal claim. Nor are we invit­ing ar­gu­ment. We’re merely re­port­ing that there is a long­stand­ing con­ven­tion grounded in pro­fes­sional prac­tice: one space. We’re not of­fer­ing a deeper jus­ti­fi­ca­tion for this rule, any more than a dic­tio­nary tries to jus­tify why cough, tough, dough, and through don’t rhyme. I’m not even claim­ing the rule has al­ways been thus (it hasn’t) or al­ways will be (ty­po­graphic prac­tice changes, al­though slowly). But in the here & now, the prac­tice—and there­fore the rule—is clear.

Hav­ing yielded this ground, I do think the study au­thors err by open­ing with the flawed premise “There has been a long de­bate on the topic of how many spaces should fol­low a pe­riod” and then sum­ma­riz­ing the “ar­gu­ments ... on both sides”. This is a du­bi­ous ful­crum for a sci­en­tific ar­gu­ment, be­cause it sets up a false equiv­a­lence. What would we think if a pa­per started “There has been a long de­bate about whether men landed on the moon …”? The fact that cer­tain peo­ple on Red­dit have long de­bated a topic does not mean there’s “a long de­bate” in the rea­son­able-per­son sense. It would seem fairer to ad­mit “The es­tab­lished prac­tice is one space, though a de­voted mi­nor­ity still ad­vo­cates for two. We wanted to find out: is there an em­pir­i­cal difference?”

The er­ror of false equiv­a­lence also makes me won­der about the true mo­ti­va­tions for this study. The au­thors seem in­ter­ested in vin­di­cat­ing the Amer­i­can Psy­cho­log­i­cal As­so­ci­a­tion, a promi­nent con­trar­ian that stan­dard­ized on two spaces in its style man­ual some years ago. [Though no longer—see the 2022 up­date be­low.] As the pa­per ex­plains, the APA orig­i­nally jus­ti­fied its de­ci­sion on the grounds of “ease of read­ing com­pre­hen­sion”, de­spite there be­ing “no di­rect em­pir­i­cal ev­i­dence in sup­port of these claims.” But the pa­per’s fi­nal para­graph be­gins “In sum, the cur­rent find­ings pro­vide em­pir­i­cal ev­i­dence for the change made to the APA Man­ual spec­i­fy­ing ... two spaces.” Why would any re­search psy­chol­o­gist spend time & bud­get chas­ing this down? Es­pe­cially since the APA al­ready proved it­self happy to fly in the face of pre­vail­ing habit. Mys­te­ri­ous. [Up­date: lead au­thor Re­becca John­son has con­firmed in an in­ter­view that pro­vid­ing em­pir­i­cal sup­port for the APA was a goal of the study.]

Any­how, back to the sci­ence. The study aimed to mea­sure the dif­fer­ence in read­ing ef­fi­ciency in para­graphs of text that dif­fered in the num­ber of spaces—two spaces or one—af­ter pe­ri­ods and, in­ter­est­ingly, com­mas. The sub­jects were 60 Skid­more Col­lege stu­dents “who were na­tive speak­ers of Amer­i­can Eng­lish and had nor­mal or cor­rected-to-nor­mal vi­sion.” In the study, the sub­jects first typed a para­graph of text, so the re­searchers could clas­sify each sub­ject as a ha­bit­ual one-spacer or two-spacer—also an in­ter­est­ing detail.

Af­ter that, the sub­jects were asked to read a se­ries of 20 “ex­per­i­men­tal para­graphs” rang­ing from 71–166 words. A com­pre­hen­sion ques­tion was asked af­ter each para­graph to con­firm un­der­stand­ing. This gave a mea­sure of read­ing speed and com­pre­hen­sion ac­cu­racy. Fur­ther­more, as the sub­jects read the para­graphs, an eye-track­ing de­vice cap­tured the move­ments of their right eye, pro­vid­ing fur­ther data about how the ex­tra spaces af­fected reading.

So what did these “ex­per­i­men­tal para­graphs” look like? The pa­per tells us that the para­graphs were set in “14 point Courier New font” with “quadru­ple” line spac­ing, which I’ll take to mean quadru­ple the point size = 56 point. The au­thors don’t men­tion how wide the lines were, nor the color of the type, nor the back­ground (though these de­ci­sions would also af­fect readability).

So here’s my best guess of how that text looked, us­ing a para­graph of 89 words:

The para­graphs were not printed, but rather dis­played on a “21 inch NEC Ac­cu­Sync 120 mon­i­tor” run­ning Win­dows (ver­sion not spec­i­fied). This CRT dis­play, first made in 2002, sup­ports a max­i­mum 1600 × 1200 res­o­lu­tion. CRTs, how­ever, can be op­er­ated at mul­ti­ple res­o­lu­tions, and the pa­per doesn’t men­tion ex­actly which was used—an­other de­ci­sion that would af­fect read­abil­ity, since it would change the ap­par­ent size of the font. Still, pretty much what you’d ex­pect to find in the psy­chol­ogy lab of a lib­eral-arts col­lege—equip­ment handed down two up­grade cy­cles ago—though not what most read­ers are us­ing today.

To get a truer fla­vor of the ac­tual pixel dis­play, here’s the same text from above, dis­played by a Win­dows XP emulator:

At the out­set, I said I ac­cepted the study and its find­ings. Still, I can’t avoid point­ing out that this style of ty­pog­ra­phy is nei­ther com­mon nor re­al­is­tic—not the mono­spaced font, not the point size, and not the line spac­ing. (Cer­tainly, this sam­ple para­graph doesn’t com­port with the most ba­sic ad­vice about body text given here at Prac­ti­cal Ty­pog­ra­phy.) Maybe those dif­fer­ences help iso­late the is­sue of two spaces vs. one. Or maybe they con­found it, by mak­ing the sur­round­ing text more dif­fi­cult to read. Con­sider that in an ear­lier read­ing study, lead re­searcher Re­becca John­son used nor­mally spaced Calibri.

Am I be­ing un­fair? I don’t think so. Re­searchers in­clude these de­tails so that oth­ers can as­sess the cred­i­bil­ity of their meth­ods, and there­fore their find­ings. The two are in­ex­tri­ca­bly teth­ered. But no ty­pog­ra­pher would de­fend the leg­i­bil­ity of Win­dows text on a CRT dis­play from 2002. It was aw­ful then, and worse now. To­day, even an en­try-level smart­phone screen is eas­ier to read. And al­though no mono­spaced font is a mir­a­cle of leg­i­bil­ity, Courier New is one of the worst—I de­scribed it as “beastly ... spindly, lumpy, and just plain ugly.”

There’s no ev­i­dence that the re­searchers con­sulted a ty­pog­ra­pher on the de­sign of their study. I wish they had. Not be­cause ty­pog­ra­phers know best. Rather, be­cause that col­lab­o­ra­tion might’ve pro­duced test cases that led to more fruit­ful re­sults. As it stands, the re­searchers ended up test­ing the leg­i­bil­ity of type­writer habits. Given that a com­puter can dis­play any font, at any size, I would’ve pre­ferred that they use a wider ty­po­graphic va­ri­ety. Given how easy it would’ve been to pre­pare printed sam­ples, I would’ve pre­ferred that they not rely strictly on an an­cient CRT.

But as I said—I’m not the ty­pog­ra­phy po­lice. And I’m def­i­nitely not the ty­pog­ra­phy-re­search po­lice. Though I ac­cept the find­ings of the study, the ty­po­graphic con­di­tions seem overly—and un­nec­es­sar­ily—ar­ti­fi­cial. Yes, sci­ence is real. But that cuts both ways. We com­mit to fol­low the ev­i­dence wher­ever it leads. But some­times it doesn’t lead very far be­fore the trail goes cold.

To be fair to the au­thors, they don’t over­sell their find­ings. (Well, aside from the ex­pec­ta­tions set by their cho­sen ti­tle.) Ac­cord­ing to the study, there were “sta­tis­ti­cally re­li­able and ... de­tectable” im­prove­ments due to two spaces af­ter a pe­riod: cer­tain re­search sub­jects were able to read the pas­sages faster with­out los­ing comprehension.

But that con­clu­sion comes with some sig­nif­i­cant caveats:

• The mea­sured im­prove­ment was in read­ing speed, not read­ing com­pre­hen­sion, and was “small in mag­ni­tude”—about 3%.

• “Com­pre­hen­sion ac­cu­racy was high across all con­di­tions.” Mean­ing, read­ing com­pre­hen­sion was not bet­ter with two spaces vs. one.

• “The pas­sages .... were rel­a­tively short and may not have been long enough or dif­fi­cult enough to de­tect sub­tle dif­fer­ences” be­tween one space and two.

• The au­thors ac­knowl­edge the prob­lem I men­tion above: that “the para­graphs ... were pre­sented in a mono­spaced” font and that “word proces­sors to­day uti­lize pro­por­tional fonts”.

• They also ac­knowl­edge my broader point about the nat­u­ral­ism of the sam­ples, and that re­sults “may dif­fer when pre­sented in other font con­di­tions (or other writ­ing systems).”

But here’s the show­stop­per. Re­call that the re­searchers sep­a­rated sub­jects into two groups: one-spac­ers (i.e., those who or­di­nar­ily typed with one space) and two-spac­ers. The “small” im­prove­ment in read­ing speed was only de­tected among sub­jects “who al­ready type ac­cord­ing to this two-space con­ven­tion”. For one-spac­ers, there was no ben­e­fit at all.

For me, this dif­fer­ence be­tween the read­ing per­for­mance of one-spac­ers and two-spac­ers was the most in­ter­est­ing part of the study. Here’s the chart show­ing how each group per­formed (one-spac­ers on the left, two-spac­ers on the right):

No­tice four things about the chart—

1. Among the one-spac­ers, read­ing speed was ba­si­cally the same re­gard­less of punc­tu­a­tion spacing.

2. Among the two-spac­ers, the big im­prove­ment in read­ing speed came when read­ing text with the punc­tu­a­tion spac­ing that matched their own typ­ing style—that is, two spaces af­ter pe­ri­ods, and one space af­ter commas.

3. No par­tic­u­lar punc­tu­a­tion spac­ing im­proved or re­duced read­ing speed for both groups.

4. And here’s the big one—two-spac­ers were faster read­ers than one-spac­ers re­gard­less of punc­tu­a­tion spac­ing! This hoists a gi­ant red flag that the out­come of this study was de­ter­mined not by punc­tu­a­tion spac­ing, but other fac­tors not di­rectly tested.

No, I’m not pre­pared to the­o­rize why two-spac­ers seem to be gen­er­ally faster read­ers than one-spac­ers. I’ll leave that for the in­ter­net hordes to ar­gue for the next few years. It’ll be a nice change of pace.

Mean­while, my ad­vice will re­main the same: one space be­tween sen­tences. Inas­much as the study showed a ben­e­fit for only one sub­set of read­ers, I’ll de­clare Bet­teridge’s Law safe as well. Are two spaces bet­ter than one? No. I just saved you $39.95.

—Matthew But­t­er­ick
30 April 2018

As of the 7th edi­tion of the APA Pub­li­ca­tion Man­ual, of­fi­cial APA style now calls for one space af­ter a pe­riod. As to the ques­tion posed at the be­gin­ning—are two spaces bet­ter than one?—we now have the APA’s an­swer: no.