Strategies for Usability
Strategies that maximize usability must do the following:
- Reduce the burden on the short-term memory of the reader. Research shows that the average person can retain 7 ± 2 chunks of information in short-term memory. This does not necessarily mean that you must limit sentence lengths to seven words. You can group words together in familiar patterns to form single chunks of information. However, research also shows that a sentence length of more than 25 words overwhelms short-term memory.
- Build understanding and recognition of terms and structures into long-term memory. Research shows that consistent usage is the best way to achieve this goal. The more information that the reader stores in long-term memory, the lower the burden on the short-term memory.
- Provide clear navigation techniques.
8.3.1. Eliminate Superfluous Information
Superfluous information gives rise to the following usability issues:
- Increases the amount of text that a reader has to understand before reaching the required information.
- Increases the amount of time and effort that a reader has to invest to access information.
- Takes up space in the short-term memory of the reader.
- Drains mental resources. The reader has a limited amount of mental resources. The more mental resources that reading the documentation takes up, the less mental resources are available for the reader to perform the required actions.
- Introduces the potential for confusion.
- Unnecessary adjectives and adverbs
- Additional sentences that explain a concept in a slightly different way
- Information about other topics that is not relevant
- Personal opinions
- Speculation about future product functions
- Rhetorical questions
- Over-exposed legal information
- Over-exposed author information
8.3.2. Create Consistent Structures
Create your documentation with repeated structures, using the same hierarchy of sections and the same type of information in the sections. By repeating the hierarchy of information structure throughout a documentation set, you train the user to look for certain types of information in certain places.
The structure of the documentation is like a street map. Obviously, a street map that is consistent across the whole of a city area is a better navigation tool than a street map that is inconsistent. The intrinsic, repeated structure of your document needs to feature all of the following characteristics:
8.3.3. Use Modular Information Blocks
Create modules that are short enough to reduce scrolling or page-turning to a minimum. Aim to eliminate scrolling or page turning completely for each individual module of information.
8.3.4. Use Consistent Language
At school, teachers tell you to vary your writing so as to hold the interest of the reader. Technical documentation requires the opposite approach. Use the same vocabulary for the same purpose throughout your documentation. Furthermore, when a team of writers work together, they must write with a single voice.
You expect the terminology in a street map to be the same for the whole map. You do not expect particular areas of the map to have personalized terminology. Similarly, use of consistent language by a team of writers across the whole documentation set ensures that the reader is not confused by conflicting terminology.
Repeated use of consistent language builds long-term memory, and therefore reduces the demand on short-term memory. The reader can access the real information content of your text.
Other language points that you need to consider:
- Research shows that words with Latin and Greek roots are harder to understand than equivalent plain English words.
- Do not use non-English words, for example, Latin terms. Some readers might not understand the non-English word. Even readers that do understand the non-English word might need to pause and think about such a word.
- Short words are easier to process in short-term memory than long words.
- The active voice is easier to understand than the passive voice.
8.3.5. Use Consistent Typographic Conventions
Where documentation structure is like a street map, typographic conventions are like street signs and road markings. Typographic conventions such as capitalization rules, punctuation, and emphasis tell readers what to expect. Consistent typographic conventions provide the inner structure of a documentation set. Inconsistent typographic conventions confuse and distract the reader.
Imagine the confusion if one area of a city uses different street signs and road markings than other areas. Or worse, imagine the chaos if one area of a city uses the same road markings as everywhere else, but to mean different things. No-one is in danger from inconsistent typographical conventions in a manual, however readers might not revisit the documentation if the conventions are confusing.