1. 1 CMT 3210: Understanding the human element in HCI Lecture 4 Models of human-Computer Interaction Mental Models Elke Duncker

2. 2 Models of Human-Computer Interaction zNormans 7 stage model zHuman Processor model

3. 3 Evaluation and execution zApproximate model of how people carry out tasks zEmphasises carrying out actions and getting feedback The World Goal Evaluation: Comparing what happened with what we wanted Execution: Carrying out actions on the world

4. 4 The World Perception Cyclic model of human action zSeven stage process zCan start anywhere Goal Intention formation Action specification Execution Evaluation Interpretation

5. 5 Gulfs of execution and evaluation zGulf of execution: yHow does the user translate intentions into action? zGulf of evaluation: yHow does the user understand the effects of actions and does s/he tell when her/his goals are satisfied? GoalsWorld Execution Evaluation

6. 6 Bridging the gulfs zExecution yMappings: are actions designed so the user make the connection between the effects they intend to achieve and the actions provided by the system? zEvaluation yFeedback: is information about the system state provided in a way that allows users to determine whether goals are satisfied?

7. 7 Using the model as a design aid Tell what actions are possible Determine mapping from intention to action Perform the action Tell if system in desired state Determine mapping from state to interpretation Determine the function of the device Tell what state the system is in zHow easy is it for the user to:

8. 8 Principles for good design zVisibility yof the state of device and possibilities for action? zGood conceptual model yconsistent presentation, coherent system image? zGood mappings yrelation between actions and effects? zFeedback yabout effects of actions?

9. 9 A model of human information processing Model Human Processor zDetailed model of how computer users process information zIntended to help designers do predictions zConsists of specialised concurrent processing units and memories ycharacterised by speed, decay time, capacity, encoding

10. 10 Model Human Processor Working memory Long-term memory Auditory memory Visual memory Stimulus Perception Cognitive processo r Motor processo r

11. 11 Principles of the MHP zPerception takes time - depends on stimulus intensity zProcessing takes time - depends on task demands, information load, practice zDifferent encoding used at different stages zUsers act rationally (most of the time): Goals + Task + Operators + Inputs + Knowledge + Processor limits Behaviour

12. 12 Applications in HCI zThe GOMS and KLM analysis techniques zIdentifies kinds of processing and memory zIdentifies possible concurrency

13. 13 Comparing the models zMHP almost exclusively about what goes on inside the head yFocus on human performance - especially time zNorman's model more about human-machine interaction ywithout saying how processes are implemented or what exists in the head yDistinguish between "in the head" and "in the world"

14. 14 Knowledge in the head and in the world zKnowledge needed to translate intentions into plans and actions may be yremembered by the user (in the head) xe.g. unix commands yembedded in the devices used (in the world) xe.g. direct manipulation interfaces

15. 15 Summary HCI models zNorman's 7 stage model of human action yIdentifies processes involved in action yDoesn't specify how they take place yUseful as a tool for thinking and analysis yConsideration of "in the head" / "in the world" zModel Human Processor yDetailed account of human information processing ySpecifies how internal processes work yUsed for making predictions (e.g. GOMS) zFramework for topics that will come later

16. 16 Mental Models zA person’s image about an artefact zThe user’s image about the machine zMaking sense of the world from inside

17. 17 Mental Models  An internal representation of a system that can be interrogated and manipulated.   Mental models are concrete.   Mental models can be run.   Mental models are constructed from experience. zMental models are generally incomplete and inaccurate, but serve a purpose

18. 18 Example Camera zWhat are the components and how do they fit together? zHow does it work? zWhat causes what? zHow do you use it? zHow do you use your understanding when something goes wrong?

19. 19 Example: London Underground Map what is it good for? zwhat isn’t it much use for?

20. 20 The Contents of a Model zKieras (1982) categorised the kinds of knowledge that people have about a device as follows. yLabel or name of the device yFunction or purpose (what goals can be accomplished) yControls and indicators yInputs, outputs and connections yPower sources and requirements

21. 21 Contents of a Model (cont.) yExternal layout and appearance yInternal layout and appearance yExternal behaviour (input-output function) yHow to operate the device to accomplish goals yProcedures for troubleshooting and maintenance yInternal structure and mechanisms (how it works)

22. 22 Mental Models  A runnable mental model = how-it-works knowledge + knowledge how-to-use-the-how-it- works-knowledge !  How-it-works knowledge may be at various levels of detail. zStrategic knowledge includes various strategies — e.g. inference, prediction, diagnosis. These are transferable skills.

23. 23 Origin of mental models  a) declarative and procedural models  b) feedback, hypothesis-testing (but beware mode errors)  c) manuals and help systems  d) analogy and metaphors  e) designer’s conceptual model:

24. 24 How designers influence the user’s mental model Designer’s conceptual model Interface design User’s mental model

25. 25 Note zThis view puts the designer at the centre zIt is the designer’s job is to enable the user to assimilate their view by getting the device to project an appropriate image of itself.  This is necessary for device-only constructs (where the challenge is to make these as easy to learn and make sense of as possible).

26. 26 Domains and devices z'Mental models' are about understanding the device [and its representation of the domain]. zUser may be: zmanipulating domain through device, or zinvestigating domain through device

27. 27 Further Reading zFor the execution-evaluation model: yDonald Norman "The Design of Everyday Things” (also appeared as "The Psychology of Everyday Things") zFor the Model Human Processor: yStuart Card, Thomas Moran and Alan Newell "The Psychology of Human Computer Interaction"