Goals in the context of HCI are things that can be defined in a given context, then evaluated.

Human task involves the steps to do something, whereas human needs are general wants of the user, what they want to get accomplished. Usability goals are primarily objective, user experience goals are more subjective.

Usability Goals

Usability refers to ensuring that interactive products are easy to learn, effective to use, and enjoyable from the user’s perspective. Following 6 goals:

  1. Effective to use (effectiveness). Is the product capable of allowing people to learn, carry out their work efficiently, access the information that they need, or buy the goods that they want?
  2. Efficient to use (efficiency). Once users have learned how to use a product to carry out their tasks, can they sustain a high level of productivity?
  3. Safe to use (safety). What is the range of errors that are possible using the product, and what measures are there to permit users to recover easily from them?
  4. Having good utility (utility). Does the product provide an appropriate set of functions that will enable users to carry out all of their tasks in the way they want to do them?
  5. Easy to learn (learnability). Is it possible for the user to work out how to use the product by exploring the interface and trying certain actions? How hard will it be to learn the whole set of functions in this way? Should have good transfer effects (where knowledge acquired earlier improves one’s ability to learn/perform in another context)
  6. Easy to remember how to use (memorability). What types of interface support have been provided to help users remember how to carry out tasks, especially for products and operations they use infrequently?

Examples of commonly used usability criteria

  • time to complete a task (efficiency)
  • time to learn a task (learnability)
  • number of errors made when carrying out a task over time (memorability)

User Experience Goals

These are concerned with how users experience an interactive product from their perspective, rather than assessing how useful or productive a system is from its own perspective

Desirable aspects of UX

  • Satisfying
  • Enjoyable
  • Helpful
  • Fun
  • Provocative

Undesirable aspects of UX

  • Making one feel stupid or guilty
  • Cutesy
  • Gimmicky
  • Frustrating

These are combined in a user’s multi-faceted experience of a product

Design Principles

Generalizable abstractions intended to orient designers toward thinking about different aspects of their designs

Concerned with what users should see and do when carrying out their tasks using an interactive product: the dos and don’ts of interaction design.

  1. High visibility: ensure functions are easy to find and intuitive.
  2. Feedback: time sensitive information about what actions has been done and what has been accomplished.
  3. Constraints: ways of restricting the user interaction to those which are valid in any given moment.
  4. Consistency: an interface which follows rules, such as using the same operation to select all objects.
  5. affordance: attributes should obviously signal what they can use it for.

The problem when applying these to real world is that trade-offs can arise between principles (e.g. increased constraint might mean less visibility).