Writers have long asked whether they should use one space or two after aperiod.Pe ople often express ve- hement opinions on the matter.Th e debate is important enough to merit a Wikipedia entry (www.
Given this debate, how should a writer go about deciding
whether to use one space or two? I have identified four salient factors: 1) readability; 2) aesthetics, including consistency of appearance; 3) effort; and 4) environmental cost. Based on my review of
these factors, I recommend using one space after periods.
Before I begin this analysis, let me note that I have excluded
the recommendations of style manuals. Style manuals are not
sources of immutable law. They are merely compilations of opinions held by other mortals, as fallible as any of us. If a writer is
submitting a document to a publication that adheres to a particular style manual, then he or she should follow that manual
— not because that manual is undeniably correct but simply because the publication has chosen to adhere to that convention. I
am directing my comments here to writers who are more or less
free from the dictates of style manuals.
The first and most important factor, readability, concerns how
easily readers can comprehend a written passage. If we could
determine conclusively that either one space or two spaces
after a period resulted in improved readability, then the anal-
ysis would end there.
But no one has yet demonstrated that either one space or two
makes a document more readable. The Wikipedia entry “
Sentence Spacing Studies” reports that scientific studies fail to support either single spacing or double spacing (www.en.wikipedia.
org/wiki/Sentence_spacing_studies#leo03). I have not reviewed the original sources, but I believe that they are correct.
People do not read in linear fashion, one word at a time. Our
eyes jump rapidly, almost randomly, from one part to the other
of the visual field in movements called “saccades.” Our brains
then stitch this almost chaotic information into a more or less
coherent whole. This process is entirely unconscious: we are not
aware of the saccades or of the neurological effort that results in
our false impressions of a smooth, coherent world (see, e.g., Daniel C. Dennett, Consciousness Explained, at 54, 111–13, 354–55,
361–62 (Boston: Little, Brown, 1991)).
Because our eyes work this way, it should be no surprise that
we do not in fact read word by word, but in phrases or clumps of
words. Accordingly, it should be no surprise that relatively minor
differences in spacing have no measurable effect on readability.
The factor of aesthetics covers multiple topics. Most aesthetic
preferences devolve into mere convention or personal preference. If a writer learned to type using two spaces after a period,
The Case for One Space
Typing One Space, Not Two, After a Period
by Daniel Gunter