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I am currently reviewing the usability of some internal reports. One thing which strikes me as odd is that all the text is centered. I always prefer left-aligned text.

But apart from my personal opinion (and also apart from design aspects): is left-aligned text preferable from a usability standpoint? (left-to-right text direction assumed).

I can imagine that the eye needs to do more work with centered text (looking for the start of the next line), but I can't find any sources to support this thesis.

Edit: The linked "duplicate" question(s) cover the alignment of the content area of a webpage, this question is about the text. I don't think that this is the same problem.

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I'm not going to copy everything directly, so here's a link to a discussion on IxDA.com on this exact topic. It has references to several research studies showing why left-aligned text is better. You are essentially right — it takes more work to read centered text when going from line to line. You are also more likely to lose your place because you don't have that anchor on the line above of text that you have already read.

  • Thanks for the link. This is exactly what I was looking for! – stefan.s Jan 19 '11 at 14:38
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    This article suggests making the text more difficult to read may improve comprehension, not sure if that applies to text alignment. infoworld.com/t/collaboration/… – Tester101 Jan 19 '11 at 20:56
  • And it is worth noting that generally people prefer justified text, even though it slows down reading speed. – Splog Apr 13 '11 at 10:48
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    I haven't read it but I know its inaccessible for people with cognative impairments. – saybeano Apr 13 '11 at 23:27
  • @Splog, People prefer reading justified text? Then I must be alien. Where did you get that from? – Pacerier Sep 17 '14 at 12:49
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Charles' link looks good. Two key reasons to left align off the top of my head ...

(1) Legibility - easier to read, as you and Charles both point out above

(2) Consistency - users expect text to be left aligned - not just in digital but print formats. Only break norms to achieve a particular goal - for example, I'm not sure I would ever center text (and certainly not large bodies of text given the legibility issues) but as you point out, this both jars user expectation and requires the user to do more work in order to interpret the text, so there is the argument that in some instances this might actually be desirable - e.g. to deliberately force the user to focus on that particularly important text (such as a warning message) in order to understand why it has been given that formatting treatment.

Might also try: http://blogs.infragistics.com/ux/articles/text-treatment-and-user-experience.aspx

  • +1, Good pointer regarding centered text having more "focus". – Pacerier Sep 17 '14 at 12:57
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I'm surprised no one has mentioned the fact that this is how most western cultures teach people how to read.

We start off learning left to right reading from the top down.

It's a good practice to produce & design content based on the cultural and standard norms for your target demographic.

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    +1, though the "western culture" is not the whole world's population (not even half). – Pacerier Sep 17 '14 at 13:09
  • @Pacerier yes, but we invented the computer. "The victors write the..." future, I guess. – user67695 Apr 18 '17 at 14:37
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We can only read an area of an half inch to an inch or so before our eyeballs have to move, which involves physical effort even if it is instinctive. With text that has a vertical left-margin, our eyeballs can return to the same starting position with each new line. With centered text, the start positions of line vary and thus create extra physical/psychological strain as we locate the next line.

This limitation to our eyesight probably comes from our evolution as top-tier land-based predators; we needed sharp vision to stalk prey but we didn't need sharp vision beyond a limited central area.

  • Sources please. – Pacerier Sep 17 '14 at 12:58
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    Nah people can understand these assertions on their own; you don't need scientifically conducted research to prove or disprove everything. I know the gatekeepers of this site want to remove so-called opinions, but doing so discourages people from using their knowledge, observation, and insight to state their conclusions even if they do make sense. Limiting questions and answers to things that can only be proved or disproved by outside sources also limits the site. It also leads to what I call "intellectual laziness." – Tim Huynh Sep 22 '14 at 17:40
  • I was talking about your sources for your last paragraph... The part on evolution. – Pacerier Sep 22 '14 at 21:08
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    Conclusions about evolution can't actually be proved or disproved: you can't re-create millions of years, so you can only make educated guesses based on observation. Just look at the faces of every apex land-predator you can imagine; notice where the eyes are located on the head and positioned relative to each other. Maybe you don't believe in evolution, (and I'm not go to argue either way) but it can't be a coincidence these animals stalk prey mostly with their eyes. At the same time, they generally don't have to worry about attacks from the side or behind. How would this affect their vision? – Tim Huynh Sep 24 '14 at 15:33
  • When I say "sources please" I mean you should include explanations that support your assertions. Explanations can come in the form of text, or links to text. You should edit the answer to include the "text explanation" found in your last comment. – Pacerier Sep 24 '14 at 16:12
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Also people like straight lines, we decipher linear spaces quicker than we do unbalanced spaces as it allows our eyes to move quicker down a particular path rather than searching out frequent starting points.

Applying this to a usability perspective, retention and attention spans are critical, so having core information which is difficult for the eye to comprehend is only going to annoy people and dilute the message

See this text 4th paragraph down.

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