What are Usability Principles?

Question

In Interface and Interaction Design, what are (and what are) the principles of Usability?

Answer 1

Usability Principles (also called Heuristics) are guides or "expert advice" regarding good practices in user interface design. They come from a method called Heuristic Evaluation (proposed by Jakob Nielsen in 1990) and serve two purposes: facilitate the choice between different design alternatives during creation and allow finding and justifying problems during evaluation.

The most famous heuristics for the design of interfaces in general purpose software were proposed by Nielsen and are composed of 10 principles:

• System visibility. Always keep users informed about what happens in the system, through feedback appropriate at the right time. Features that can be used for this include mouse cursor changes, highlighting (Highlight) selection bar, information bar (status bar). But, one should avoid exaggerations or unnecessary interactions as in the example below (the results could be immediately displayed without the need to click the button):

• Correspondence between the system and the real world. Speak the user’s language, using words, phrases and concepts that are familiar to you as opposed to technical terms. Technical terms and even metaphors can be misleading. The example below is illustrative (and funny), because the interpretation of "type" (which can mean the word "type" or the verb "type") can lead a user to type M-I-S-M-A-T-C-H on the keyboard:

• Control and freedom for the user. Provide options for users to easily escape unexpected conditions by using clearly indicated "emergency exits". To achieve this, provide the undo option (undo) actions and allow long operations to be canceled. But do so clearly, probably by directly providing a cancellation option. Even the dialog below is confusing because it does not present a button called "Cancel" and still presents the textual indication using words that are not found in the buttons presented:

• Consistency and standards. Avoid making users need to think about different words, situations or actions that may have the same meaning. The idea is to maintain the same appearance and behavior (look and Feel) throughout the system, so that similar things look similar and different things look different. It may seem simple, but it is a very common error as in the example below involving the positioning of buttons:

• Error diagnosis and recovery. Use simple, constructive, polished language to describe the nature of a problem and suggest a way to solve it. The example below calls the user an idiot, increasing his frustration with the misunderstanding of the interface and greatly damaging his experience with the product:

• Error prevention. Wherever possible, prevent errors from occurring first. This can be done by disabling temporarily inaccessible or illegal commands and using checkboxes (such as combos and lists) instead of text boxes, as they are less prone to errors because the user has no way of misspelling the content. Still, this should not be used to the extreme as in this example (where there is no gain in data entry accuracy, but there is loss in task execution efficiency):

• Recognition instead of memory. Make objects, actions and options visible. This means that graphic components should be used in the conventional way (selection by combos and lists and not by text boxes, for example) and one should avoid asking the user to keep a lot of information in memory. In the example below, once the user clicks OK, the entire indicated path will be immediately deleted from the screen, but if this information is important it should remain displayed visually (with the use of balloons or the automatic opening of the specified window):

• Flexibility and efficiency in use. Provide accelerators that are invisible to novice users, but allow experienced users to perform their tasks faster. Classic examples are shortcut keys and quick access menus:

• Minimalist design and aesthetics. Avoid using information that is irrelevant or rarely used. Additionally, use simple, easy-to-understand colors and fonts, and arrange the elements to occupy spaces consistent with their functions (i.e., do not display disconnected information in the same window). In the example below, the command bars demonstrate bad and good button grouping practices, and the window demonstrates a bad practice in displaying unrelated information in a single view:

• Help and documentation. Provide means for information to be easily sought and provide help in concrete steps that can be easily followed. Classic examples of good practice are context help (where the user uses F1, a conventional key, to display information about the currently selected field) and information balloons that indicate the visual element to which they relate.

It is important to mention that these are some of the classic Usability principles used in software development (there are others mentioned in the Wikipedia article on heuristic evaluation^en), but that the choice of a set of heuristics definitive is open to discussion, mainly because its applicability depends heavily on the field of application.

In digital games (video games), for example, certain aspects of Usability are less important or are intentionally missed because it aims to produce the User Experience (UX) of fun. For example, certain game elements are built to be intentionally harder to execute or remember, although other aspects such as feedback remain important. Thus, in the case of entertainment products there are more famous heuristics, based on classical utilitarian heuristics but extending them to include hedonic aspects (not utilities).

A first example is the taxonomy of MDA model (of Model-Design-Aesthetics) which includes the following principles related to amusement static:

• Sensation. Game as sensory pleasure.
• Fantasy. I play like make-believe.
• Narrative. Play as drama.
• Defiance. Game as course of obstacles.
• Companionship. Game as a social framework.
• Discovery. Game as unexplored territory.
• Expression. Game as self-discovery.
• Submissiveness. Game as a hobby.

And another famous example is the model Gameflow, based on the Theory of Optimal Experience (Flow) and that includes among other heuristics the seguines (the details are accessible in the referenced paper):

• Concentration. Games should provide stimuli from different backgrounds that are significant to the player’s attention. Players should be able to stay focused on the task, without being overwhelmed with too much information, and should not be distracted from the tasks they wish or need to perform.
• Defiance. Challenge in games must be in accordance with the skill level of the players, provide different levels of difficulty and provide feedback on the progress of achieving the goals.
• Control. Players must be able to choose their goals and actions and feel responsible for the results of the game. They should not be able to make mistakes that break their immersion in fantasy and narrative.

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Main sources:

• Preece, Rogers and Sharp. Interaction Design: Beyond Human - Computer Interaction.
• Hall of Shame interface (image source)
• Miller. Lecture 5 on Heuristic Evaluation

Answer 2

Much has been discussed about Nielsen’s 10 Heuristics on Usability, I do not intend to re-discover the wheel. On the contrary, I also want to bring to my posts such premises and emphasize their importance. My goal with this post is to be able to deal with these Heuristics in other posts and referencing them through link, thus facilitating understanding.

But after all, quickly speaking, what is Heuristics? This word has Greek origin, heuristic, and has the same ethnological basis as Eureka, in short, it is associated with discovery. It is important to understand this because such a word for many is more a dirty word, when we deal with the subject in some debates and speak "heuristics" there are those who ignore the term look suspicious, as if we were using a strange word to justify a "superior" knowledge. And that’s not it, it’s a word that exemplifies well what is done in the field of Usability, day after day we discover the right paths for developing systems, apps, websites, etc. And often during the creation process we have our insight, where we could easily shout Eureka. Now, why reinvent the wheel if we can actually follow some premises of those who came before us and on the basis of study came to conclusions... heuristics. ;) According to Jackob Nielsen. "These are the ten general principles of user interface design. They are called "heuristics" because they are more in the nature of rules than as specific usability guidelines." Clarifying, it is a vision for the study itself, than a single and immutable guideline. 1. Visibility of system status The system should always keep users informed about what is happening, through appropriate feedback and in a reasonable time.

1. Correspondence between the system and the real world The system should speak the language of the users, with words, phrases and concepts familiar to the user, rather than terms oriented to the system. Follow real-world conventions, making the information that appears in a natural and logical order.

2. User control and freedom Users often choose some system functions by mistake and will always need a clearly marked "emergency exit" to get out of that unwanted state without having to go through an extensive "dialogue". Undo and redo support.

3. Consistency and standards Users do not need to guess that different words, situations or actions mean the same thing. Follow the platform conventions.

4. Error prevention Even better than good error messages is a careful design that prevents this error from occurring first. Eliminating or verifying error-prone conditions presented users with a confirmation option before committing to a particular action.

5. Recognition instead of memory Minimize user memory load by making objects, actions and options visible. The user should not have to remember the information from one part of the dialog to another. System operating instructions shall be visible and easily retrievable when necessary.

6. Flexibility and efficiency of use Accelerators - invisible to the novice user - can often accelerate interaction for the experienced user, which the system can suit both inexperienced and experienced users. Allow users to customize frequent actions.

7. Aesthetics and minimalist design Dialogues should not contain information that is irrelevant or rarely necessary. Each extra unit of information in a dialogue competes with the relevant units of information and decreases its relative visibility.

8. Help users recognize, diagnose, and resolve errors Error messages should be expressed in clear language (no codes), accurately indicate the problem and constructively suggest a solution.

9. Help and documentation Even if it is better that a system can be used without documentation, it may be necessary to provide help and documentation. Any information should be easy to search for, focusing on user activity, list of concrete steps to be performed, and not be too large.

Taken from: http://www.dclick.com.br/2012/02/12/heuristica/