Understanding HCI

PACT Analysis

What is a PACT Analysis?

  • People: relevant user characteristics and skills
  • Activities: how is the activity currently carried out? Why? What can be improved?
  • Context: the environment of the activity
  • Technologies: what tools are used now, and how might new developments be used?


  1. Cognitive characteristics - level and duration of attention, perception, memory, learning abilities, cognitive capabilities, fears, personality characteristics
  2. Physical characteristics - age differences, physical abilities,
  3. What motivates, pleases and engages - affect
  4. Experience & expectations - novice v's expert
  5. Language
  6. Culture - For example, in Microsoft Excel there are two buttons, one labeled with a cross and the other a tick. In the US a tick is used for acceptance and the cross rejection, but in Ireland a tick or a cross can be used to show acceptance (e.g. a cross on a ballot paper).
  7. Special needs - blindness, colour blindness, deafness, wheel chair user
  8. Homogenous vs heterogeneous user groups - website site users are (normally) heterogeneous - many different types of people; users of a company's intranet are (generally) homogenous
  9. Discretionary vs committed users - does the user have a choice? if yes, then you need to encourage them to return
  10. Infrequent vs frequent users - if users are normally infrequent, then interface must be particularly 'helpful' as users will forget how to complete complicated tasks.


  1. Goals, tasks and actions
  2. Regular or unusual, weekly? Yearly? - frequent tasks should be easy to do; infrequent tasks should be easy to learn or remember
  3. Well-defined or vague
  4. Continuous or interrupted - user may need to 'find their place' again
  5. Current task practices
  6. Individual vs co-operative work
  7. Multi-tasking vs serial tasks
  8. Passive vs active,
  9. Quality vs quantity trade-off
  10. Data input requirements
  11. Length of time on tasks - peaks and troughs of working, need for fast response
  12. Coping with errors - presentation of error messages, how to deal with them, how the system accommodates them, significance of errors, safety critical errors


  1. Physical environments - noisy, cold, wet, dirty, stressful, uses dangerous materials, sunny
  2. Social environments - channels of communication, structure,centralisation vs decentralisation, home, mobile, training materials
  3. Organisational context - relationships with customers, other staff, effect on work practices and job content, role, deskilling, job loss, shift in power
  4. Circumstances under which activities happen (time, place, pressure of work/time)
  5. Amount and type of support for activities - tuition, manuals, demonstrations, new knowledge, new skills


  1. Input - Getting data in; getting commands; security
  2. Output - Characteristics of different displays (e.g. video vs. photographs; speech vs. screen)
  3. Communications - Between people, between devices, speed, etc. - What is connected to what?
  4. Size of screen
  5. GUI or not?
  6. Sound?
  7. Networked or stand alone.
  8. Always on or dial in?
  9. Real-time systems;
  10. Safety critical systems;
  11. Walk-up-and-use systems (e.g. kiosks) / Office systems / Palm pilot application / Web site.

Why Use it?

  1. More detailed design brief
  2. And/or specification
  3. And/or user requirements document
  4. Key points for evaluation

Participants Needed

One or more experts needed

Task List

  1. Brainstorm the variety of P, A, C and Ts that are possible
  2. Explore design implications
  3. Look for trade-offs between combinations of PACT
  4. Think about how these might effect design

Conditions required

  1. Some information about (similar) system is required
  2. Marketing personnel may be involved also


  1. PACT analysis for a tourism website


In groups of 2/3 identify

  1. People, activities, contexts, technologies of an in-flight entertainment system using the pointers above.
  2. What are the design implications?