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?
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):