Priority Metrics Selecting and its Usability Metrics

Selecting is a basic and universal task a user can perform on almost all user interfaces today: users frequently need to be able to select objects or text in order to perform many important functions, and the ability to move quickly and seamlessly on to the next action is important for usability. Because of this, learnability, memorability, and errors are very important metrics:

• Learnability/Memorability: Due in part to its universal utility and in part to inheritance or design convergence from the original Mac OS, the action of selecting something is very similar across multiple user interfaces. The biggest differences across platforms are in the types of peripheral input/output devices (i.e. mouse, trackball, touchpad, or touch screen) that are available to the user. Because there is a natural mapping between the action and the expected results, a first-time user should be able to intuit how to select an item in any particular system with any particular device. And once a user learns to select something with certain peripherals, it should not be difficult to perform the same task on different platforms, even with a novel input. All of this also lends itself to memorability: if the user has not performed such an action recently, this information should be easily recalled.
• Efficiency/Errors: Selecting is a comparatively simple task, and therefore should be performed seamlessly and flawlessly. It is a necessary prerequisite for many functions or commands such as copying or moving files, and the more efficiently a user can perform the supporting task of selection, the more efficiently a user can continue with the desired high-level task. Errors must be minimized, as errors in selection could lead to such potentially dire consequences as deleting files or overwriting data (though modern computer systems minimize the impact of such errors system-wide by making most of them reversible). The additional selection functionality afforded by the keyboard through the Shift and Ctrl/Command keys give the user appreciably more power to perform tasks efficiently than selecting each of many individual items one at a time. With the selected items or text highlighted in a noticeable, contrasting color after selection, the difference between selected and unselected items is visible to the user, thus reducing errors.
• Satisfaction: While this metric generally does not apply, there are narrow circumstances in which it should be discussed. As a more utilitarian action, users typically do not derive direct satisfaction from selecting items in the user interface - although there could be limited satisfaction from animated or auditory feedback from the action in certain scenarios. There is a definite possibility, however, for negative satisfaction in situations in which the user becomes annoyed or upset if the mechanism for selecting items in the system is not learnable or efficient, or is unduly error-prone.

Key Characteristics What do all great selection frameworks have?

There are a few elements that should go into any good selecting process:

• First, in order to select a single target, the design should require the user to perform one action (click or tap).
• Second, in order to select multiple targets, the design should have a learnable and memorable system in place that builds on the natural mapping of the single select. For example, if the user can click to select one target, they should be able to click and drag to select multiple items.

Feedback & Visibility

One of the most important principles of interaction design that designers of a selection mechanism must follow is that of providing the user with feedback. Users must never doubt whether they did positively select what they wanted to select, and only what they wanted to select; when attempting the selection action, the user should get immediate and persistent visible and/or audible feedback as to what he or she is selecting. Similarly, what actions are possible should be immediately visible to the user; a user should readily be able to tell if what they are tapping or clicking is indeed selectable. That way, the user's mental model of what items are selectable will be consistent with the designer's mental model.

Prevent Errors

Don Norman urges designers to plan for the possibility of error, and to minimize the cost thereof to the user. Users should be forgiven if they inadvertently select the wrong items, or omit those they wished to select. These actions should also be readily reversible: that is, users should also be able to easily deselect objects that they no longer wish to be selected, or add additional items to the overall selection.

Consistency

The low-level actions that are required for selecting a certain type of object should be consistent in every possible context, as consistent behavior:

• reduces the likelhiood of error (and therefore also increases efficiency) due to arbitrary or unnatural mappings
• improves learnability for inexperienced users who can draw upon past experience when they encounter novel, but similar, situations
• increases memorability, for much the same reasons.

Inconsistent behavior risks confusing and frustrating the user, as they are incapable of formulating an adequate mental model to explain the discrepant behavior.

Shortcuts

Though there is an issue of unnatural mapping for the inexperienced user, shortcuts and commands that allow for more advanced functionality can significantly improve the efficiency of selecting for knowledgeable users. Shortcuts should be added to allow these more experienced users to do more with the system, such as by selecting a large amount of objects at once. The "Ctrl + A" keyboard command is a common shortcut used to "select all" of the items or content in a given folder, page, document, etc.

Platform-Specific Instances