Readability and appeal of justified text


If I write a document that I have to hand in to somebody (a report, summary, draft, whatever) I usually justify the text because it seems more appealing (at least to me) if it all finishes at the same length. However, now I read that it may be more difficult to read overall because lines do not seem so unique and the reader's eye may be misguided.

How do you usually hand in documents? Any advice or even scientific studies about that?

2/22/2013 1:21:00 PM

Accepted Answer

Your text of course ought to be justified. Two more things are necessary:

  • Proper hyphenation of words. This allows more even and better interword spaces.

  • Good line length, which should not exceed 66 characters per line in average. If lines are too long, the eye of a reader is often not able to move to the next line when reading the text and sometimes one line is skipped or the line is read twice, which confuses and distracts the reader.

This is not supported by a scientific study, just by hundreds of years of polishing the typography rules. To confirm this, open any well typeset book. (The ones older than 100 years work the best, because era of typewriters and computers did serious damage to good typography.)

Just an example of the same text typeset with different restrictions. The first text is the proper one, with hyphenation and micro typography. The second one has forbidden hyphenation and the third one is typeset raggedright. Only the first is acceptable, and "uneven interword spaces" is not an argument: They not really uneven to distract the reader, he actually doesn't even notice that there are any differences (click for better resolution):

click for better resolution

11/14/2016 12:46:00 PM

Stiff, P. (1996). The end of the line: a survey of unjustified typography. Information Design Journal, 8(2), 125–152.

No empirical data, but a good overview. Science would tell us that inconsistent word-spacing as a result of justification may inhibit saccadic eye movement by creating irregular “jumps” for the eye to make.

I have not read a study that supports or refutes this.

Anecdotal wisdom from the field of typography would have us believe that large gaps between consecutive lines will create vertical “rivers” of white space which draw the eye downwards as opposed to leading it to the right when the gaps between the words become larger than the space between the lines.

I have not read a study that supports or refutes this.

Anecdotal wisdom from the field of typography would also have us believe that the irregular shape of the right edge of a block of text helps us orient our eye on the page, assisting us in our return saccade to the next line.

I have not read a study that supports or refutes this.

I did however conducted a small experiment using eye tracking equipment which showed that when reading justified text, return saccades were less less accurate when compared to those while reading text set flush-left text. However, when reading the justified text, the duration of the landing fixations, and the distance of the correction saccades required in order to continue reading were very similar from line to line when compared to the landing fixations and correction saccades as seen when reading text set flush-left.

I hypothesize that this is because — despite the presence of an irregular rag in a flush-left setting — the distance and trajectory of the return saccade when reading justified text remains constant from line to line resulting in a muscle-memory of sorts.

I need to collect significantly more data to support or refute this hypothesis (feel free to scoop me. It would make a great thesis).

Long/short, what is published in typography books is largely anecdotal wisdom, not supported by scientific research. And the bulk of the research that is out there is very new, requiring further exploration before claims of any confidence can be made. For example, there is still no agreement regarding the legibility of serif compared sans-serif typefaces.

For a collection of peer-reviewed journal articles regarding typography and reading comprehension, see

(and I always set text flush left)