How to test readability

Legibility is the ease with which a user can not only read the text, but also understand it. In my experience as a UX designer, I saw it as the most overlooked part of user experience. Many times I participated in usability tests checking if it’s easy to find some information in an app or click on some elements on the website, but hardly ever in the ones focusing on checking if the choice of typography helps of disturbs users in consuming the content. That’s a pity, so in order to evangelize enhancing user experience of reading, I put together this simple how-to article after reading which you will be able to run your first legibility test today.

This method is of great use for teams who create products whose users mainly interact with them not by clicking or tapping on the interface, but reading the text. To name a few examples these can be:

  • landing pages
  • digital media sites (newspapers, magazines and such)
  • customer care sites like FAQs
  • customer review pages
  • product pages with descriptions about a product such as:
  • how something works: (how to use a product for instance a medicine in pharma; who is a product for in cosmetic business; how to put together a piece of furniture; product specification in electronics; how to change subscription in telco and subscription based services).

From as early as the invention of writing people try to create those golden rules of text that make it the most readable. Throughout centuries scriptors and later on printmakers and finally web designers made efforts to establish the golden ratio of text size to line height and column length. Type designer has made tremendous efforts to optimize kerning to x-height and counter to create the most readable fonts.

Apart from the choice of font, there are several factors that can improve or decrease readability. Among these are primarily:

  • font size
  • leading (something that is also called line height)
  • line width
  • justification
  • color of text
  • case usage (capitalized or lower-case letters)

Coming back to design, when you are about to test readability of your design, you probably have a couple of ideas or versions how text should be displayed. In order to run a test, prepare the same kind of text in the same layout, but in the versions that differ from one another with only one variable.

What proves that the text is readable is the fact that people can get it’s message clear. Define what is the message in the text that the users need to understand to asses the text as readable — these can specific key words that create the main message of the paragraphs you display in the text to the users.

The method that comes at hand is a modified version of 5 second test. That’s a simple usability method that allows to recall the first impressions users got during a 5 second interaction with a piece design. 5 seconds is usually too short to read a short paragraph, so I’d recommend to extend it to 10 seconds.

The number of keywords that you picked create the full score a tester can get in the test as point goes for one keyword. However, testers might use synonymous words in their answers. For instance, instead of replying “The course is for free” they can say “There is no charge for the bootcamp”. Then for synonymous phrases you also assign a point.

The initial goal of the test in the example was to check which of 4 text formatting concepts is the best. In one test, you can test two versions one after another that differ with one factor, f.ex. font weight. In order to get more precise results, change the order in which you show versions to the testers — the second read is going to be easier anyway, because users know what are the questions they did not answer and they read the text already.

In order to make it lean, during everyday work I’d recommend not to overdo it with formal recruitment of big groups of participants as that can effectively stop you from running any test at all. The number of participants most commonly used in usability testing is 5 and that perfectly fits for this case as well.

In readability tests you want to find out if the design of the text makes it easy to be read by people. It happens that reading is a skill that quite commonly spread in modern society, so recruiting participants to this kind of text is no big hustle. Demographics is not a determining thing in those tests, so it’s very easy to recruit participants who meet criteria for this particular test. I’d rather refrain from asking for help your 97-year old grandpa or 5-year old kid as reading can be a bit problematic for people of certain age, but as long as your participants have already learnt how to read and do not have sight deficiencies, they are a fit. I’d also refrain though from recruiting people who work with you on the same project, because they already know what it is about.

It happens that both fonts or text formatting concepts do not bring you to perfect results in readability test. Then it’s good to experiment with other factors that influence it, the key being line height and column length.

Categorized as UX

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