Is left-aligned text generally preferable over centered text?

Question

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.

Answer 1

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.

Answer 2

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

Answer 3

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.

Answer 4

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.