The five usability objectives are learnability, efficiency, memorability, errors, and satisfaction. Together, they provide criteria for judging how easily, quickly, reliably, and pleasantly a user can interact with a product.
How the Objectives Work
In user-centred design, designers identify user needs and test prototypes with representative users. The five objectives turn usability into measurable criteria, allowing designers to collect evidence and refine the product iteratively.
| Usability objective | Meaning | Possible evidence from testing |
|---|---|---|
| Learnability | How easily a first-time user can understand and operate the product. | Time or number of attempts needed to complete a task for the first time. |
| Efficiency | How quickly and with how little effort an experienced user can complete tasks. | Task-completion time, number of actions, or physical effort required. |
| Memorability | How easily a user can operate the product after not using it for some time. | Successful task completion after a period without use. |
| Errors | The frequency and severity of user errors, and how easily users can recognize and recover from them. | Number of errors, consequences of errors, and recovery time. |
| Satisfaction | How comfortable, acceptable, and pleasant users find the experience. | Questionnaires, interviews, ratings, and observations of frustration. |
The objectives can interact. For example, keyboard shortcuts may improve efficiency for experienced users but reduce learnability for first-time users unless labels or instructions are provided. Designers may therefore need to balance objectives for the intended target market.
A common misconception is that “errors” means a product must eliminate every possible mistake. Instead, designers should reduce error frequency and severity while supporting recovery through feedback, warnings, confirmation prompts, or an undo function.
Exam Technique
For B1.1 User-centred design, define each objective precisely and apply it to a named product. For an “explain” question, link a design feature to its effect on users; for an “evaluate” question, use testing evidence and discuss trade-offs rather than simply listing the five objectives.