Report compiled by John S. Rhodes
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 " ". 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:
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.
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:
This same writer went on to tell me that the use of two spaces is visually distracting, and can be a typographic design danger:
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.
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:
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
Eye tracking researcher Dr. Keith Rayner had this to say:
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.
Jason Thomas of Creative Mercenary and Sara Davidson both recommended these two books:
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:
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.
On 15-May Sam Harris of areader.com sent me this interesting bit of information about the use of two spaces:
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 <firstname.lastname@example.org>
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