WebWord.com > Reports > One Versus Two Spaces After a Period (13-May-99)

One Versus Two Spaces After a Period

Report compiled by John S. Rhodes
13-May-99

In late September 1998 I asked several people what I thought was a simple typographic question. I was thinking about doing a quick eye tracking study with a colleague and I wondered if there was any empirical research available that showed that a single space after a period was "better" than two spaces, or vice versa. While I was most interested in this as a web usability issue, many folks were very interested in this for all sorts of reasons. In any event, I received a flood of email about this question and now, after a long delay, I will share my results with you.

While this was originally a question about web usability, I realized that the spacing issue is basically irrelevant! Steve Outing of Planetary News correctly pointed out that almost all browsers will only render one space after the period, regardless of how many spaces you put into the HTML code. Note however, that spaces can be hard-coded into the HTML using "&nbsp". However, in terms of usability, Jakob Nielsen of the Nielsen Norman Group emphatically stated that there are many, many better ways to improve web usability. Here's a quote from Travis Wall that drives a similar message home:

"A major problem with onscreen displays is that they are too flexible -- I can specify any font I want at any size I want and that will blow to hell what the designer planned so carefully."

So, I humbly admit that this is more of a fact-finding report than a web usability rant. Use the information as you wish. There is plenty to sift through.

One of the next things I realized is that, in general, the spacing after a period will be irrelevant since most fonts used today are proportional. That is, each character is not the same size. Amy Gahran of Contentious kindly indicated that very few monospaced (i.e., non-proportional) fonts are used today on the Internet, except for perhaps Courier. This is generally the case offline as well. Proportional fonts are used much more often. For your information, I did not get any good feedback about the various fonts that are used for other Internet applications and activities, such as chat rooms and email. My guess is that they are mostly monospaced, but it is just a guess.

Like Amy Gahran, Kathy Gill told me that the current typographic standard for a single space after the period is a reflection of the power of proportionally spaced fonts.

"The only reason that two spaces were used after a period during the 'typewriter' age was because original typewriters had monospaced fonts -- the extra space was needed for the eye to pick up on the beginning of a new sentence. That need is negated w/proportional space type, hence [it is] the typographic standard."

While I'm on the topic, here's what one of the folks at The Design & Publishing Center had to say about the history of typographic spacing:

"In the days of typewriter manuscripts the extra space was necessary to separate the ends and beginnings of sentences. The space character never changed. With the advent of electronic typesetting, the software attempts to 'fit' the type to specific line lengths, it both expands or contracts the available space to make the type fit. Word spacing is where most of this space 'play' takes place."

This same writer went on to tell me that the use of two spaces is visually distracting, and can be a typographic design danger:

"With two spaces, there is 'more' space to play with, and if space is added (which is most often the case) the results are white spots, and in some cases "rivers" of blank spots in the body of text. This makes the body both unattractive as a visual element, and distracting to read."

Many people told me about the various rules and style guides they follow. Similarly, several people indicated that etiquette is an important consideration for spacing after a period. Apparently, the vast majority of these guides tell writers to use a single space. From what I am told, very little reason is given for this stylistic requirement. However, this doesn't mean that folks like David Siegel, writer of the popular Creating Killer Web Sites, isn't fanatical about using a single space. In short, the "rivers" of whitespace, caused by using two spaces, invariably annoy graphic designers and typographers. Well, at least the ones that contacted me.

Research

Gary Perlman of the HCI Bibliography found some interesting older research that does not deal with the issue of one versus two periods per se, however, it does examine some related issues. Namely, it addresses the separation of information into units of thought. I suppose that it could be interpreted and applied in light of the central spacing question. In any event, I particularly like item #4 in the abstract about blackening words (i.e., boldfacing). As many folks know, this is an effective visual device to improve readability on the Web. And, as you can tell from this report, I use boldface for all of my web writing. Right. Here's the resource:

Authors: Walter Dearborn, Philip Johnston, L. Carmichael
Title: Improving the readability of typewritten manuscripts.
Source: Proceedings of the National Academy of Sciences. Washington,
37, 1951, 670-672.

Abstract: Improved reading speed and intelligibility were demonstrated on almost 200 college students when mss. were prepared according to these rules developed in a long-term research program: (1) capitalize entirely (i.e. stress) the one word in each sentence which would be given maximal stress when read aloud, (2) use 2 columns of single-spaced lines, (3) break sentences up with spaces between units of thought, (4) blacken important sections by over-typing on them.

Dr. Jack Richman sent me a pointer to some research that might be useful to folks that are interested in reading and the development of automaticity (i.e., automatic processing of information):

Author: Dennis Fisher
Title: Spatial and contextual factors in beginning reading: Evidence for
PSG-CSG complements to developing automaticity?
Source: Memory & Cognition. Vol 5(2) 247-251, Mar 1977.

Abstract: Two experiments were designed to examine the development of spatial and contextual sensitivity during early reading. 22 2nd and 22 5th graders read 2nd- and 5th-grade level paragraphs that were either normally typed or had the spaces between the words filled. Both groups read the 2nd-grade paragraphs and the normally typed paragraphs fastest, while the filled 5th-grade paragraphs were read slowest. Data are interpreted as evidence for a skill acquisition hierarchy that attempts to resolve contradictions previously reported by J. Hochberg (1970), while providing a good complement to D. LaBerge and S. J. Samuel's (1974) notions of automaticity.

Eye tracking researcher Dr. Keith Rayner had this to say:

"With respect to the issue of spacing between words, see Rayner, Fischer, and Pollatsek (Vision Research, 1998, 38, 1129-1144). In 1975, I have a paper in Acta Psychologica that points out that readers skip over the spaces between sentences. You should also see a 1972 Reading Research Quarterly paper by Abrams and Zuber."

I admit that I was not able to follow up on Keith's references so I cannot give you any more details. However, judging from the quality of his work that I have read, these references are certainly excellent resources for folks looking for hard data. While it doesn't seem as though these papers directly address the one versus two space question, they are probably about as close as you can get.

Other Resources

Jason Thomas of Creative Mercenary and Sara Davidson both recommended these two books:

1. The Mac Is Not a Typewriter by Robin Williams
   (see the book at Amazon.com)

2. The PC Is Not a Typewriter by Robin Williams
   (see the book at Amazon.com)

Elizabeth Gee, Human Factors Engineer at the Corillian Corporation, pointed out that The Elements of Style is a standard used in schools and in businesses. And, while you are at it, don't forget about The Chicago Manual of Style. As a side note, both of these guides are selling very well at Amazon. So, it seems as though some people are trying to combat poor writing.

Here is a short list of web resources:

1. Typography on the Web (Microsoft's site on the topic)

2. Visual contrast and page design (Yale Style Guide--Typography)

3. Type and Typography in the Nineties

4. Ten common mistakes in the typesetting of technical documents

5. Typofile Magazine (by Will Harris)

6. Typography on the web

7. The FontSite (digital typography and design)

If you know of a typography site that offers information that these sites don't, please contact me. I'd be happy to add the information to improve this resource.

Addendum:

On 15-May Sam Harris of areader.com sent me this interesting bit of information about the use of two spaces:

"In older documents printed in the US, you find it frequently, until the advent of the lead-casting Linotype machine.

The linotype used wedges for spaces, rectangles for letters. After filling the line as close as possible, the operator would pull a handle, and the wedges would be forced upward, expanding (and thereby justifying) the line o' type, which would then be cast in lead.

If the operator typed two spaces in a row, you had two wedges next to each other, and that tended to gum up the operation. Clients who insisted could be accommodated by typing an en-space followed by a justifier-space, but printers charged extra for it and ridiculed it as 'French Spacing, oo-la-la, you want it all fancy, huh? Well it'll cost ya, bub, and plenty too...' and soon it became unfashionable in the US.

Commerce, as usual, was the engine of change."

Final Thoughts!

Do you want my recommendation? If you can't decide for yourself based on the above information here is my advice: You should use one space. Period.

So, that's about it for now. I'd be happy to add other comments, as long as they are highly relevant. Also, if you come by some solid empirical research let me know.

I'd like to thank every person who sent me information. I tried to give most of you links, but you are legion. You have my sincere thanks. If you have questions or comments be sure to write me <john@webword.com>

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