1 Elke Duncker CMT 3210 Designing Interactive Systems Week 5: Conceptual Models Rationality and Planning Cognitive Walkthrough

2 Today’s lecture zConceptual models zHow user choose what to do: rationality and planning

3 What is a conceptual model? zA conceptual model describes how a system is understood to function. zTwo of conceptual models: yUser model: How users think the system works yDesign model: How designers think the systems works

4 Mental Models and Metaphors zPeople use prior knowledge to develop mental models zComputing metaphors capitalise on this process. zThey use familiar object to give an intuitive understanding of an interface zProblem: finding appropriate metaphors

5 Other ways zAim: to help users to develop accurate/appropriate mental models of a system zDevelop a design model that zHelps the user to develop a mental model of the system such that the zUser model becomes consistent with the design model zSystem image

6 Conceptual Models Norman and Draper, 1986:46, quoted from Preece 2000:152 Designer User Documentation System Design model User model System Image

7 zUsers find out about the design model through ythe user interface, ythe systems behaviour. yThe documentation (if present) zUsers learn from experiencing the system zSystem image conveys design model to the user

8 What happens if… z…the system image does not convey the design model? z…the user model does not fit the design model? z…the design model is inappropriate to the domain problem?

9 Rationality and planning zPeople make decisions: zEmotional aspects and rational aspects of decision making and planning. zRational aspects: several approaches

10 What is Rational? zPeople act to attain goals. yThis means that they compare the current status with their goal. yAnd re-adjust their actions and plans zWhen doing so, they consider y the structure of the task y inputs of information. zThey are hampered by ylimitations on their knowledge ylimitations on their processing capabilities.

11 Time bands of rationality:  Newell (1990) offers a way of thinking about cognition in terms of time bands:  days - months:social band  minutes - hours:rational band  0.1 seconds - seconds:cognitive band  seconds:biological band

12 Rationality and Problem Solving z Pollock (1993) : y “A rational agent has beliefs reflecting the state of its environment, and it likes or dislikes its situation. y When it finds the world not entirely to its liking, it tries to change that. yIts cognitive architecture is the mechanism whereby it chooses courses of action aimed at making the world more to its liking.”

13 Means-Ends Reasoning zIf the user knows that doing X will achieve Y under condition Z and if the user wants to achieve Y, then the user will consider doing X. zIf condition Z doesn't hold at the moment then the user will adopt achieving Z as an additional goal.  If Z already holds then X can be done immediately.

14 Task Analysis Model zGoal:A state to achieve zDevice:Tool to achieve the goal zTask:Activity necessary to achieve the goal by using the device zSubtask:Component of the task zAction:Simple, low-level task

15 GOMS model:  Goals:Things we want to achieve  Operators:Basic actions we can perform  Methods:Alternative ways of doing things  Selection rules:Ways we make decisions  N.B. GOMS considers expert behaviour, and there’s much more to cognition than that!

16 Cognitive Walkthrough zEvaluation method based on the idea that… ythe user learns about the interface in an exploratory way, ythe user has goals,  the user is applying simple means-ends reasoning.

17 Cognitive Walkthrough zEvaluation by an expert, who goes through a set task while imitating user performance

18 Preparation: We need four things 1.User description including level of experience with computers and any assumptions made by the designer 2.System description including operations and performance (e.g. paper design) 3.Task description specifying the task that the expert has to carry out from users point of view 4.Action sequence describing the system display and the user actions needed to complete the given task. One system display and one user action together are one step.

19 Process of carrying out a Cognitive Walkthrough zPrototype, user description, system description, task description and action list has to be prepared by the designer/developer zDesigner gives these document to an expert. zThe expert reads the descriptions. zThe expert carries out the task by following the action list. zThe expert asks the following questions with EACH step of the action list:

20 Questions Cognitive Walkthrough 1.Is the next goal clear at this stage? 2.Is the appropriate action obvious? 3.Is it clear that this action leads to the goal? 4.What problems are there in performing the action?

21 Example: the Automatic Nail Painter zThe automatic nail painter is a machine with which one can have one’s nails painted.

22 User Description Automatic Nail Painter zThe users are assumed to have no prior knowledge of how to operate the Automatic Nail Painter. However, they are assumed to have experience in putting nail varnish on nails manually

23 System Description Automatic Nail Painter zThe system allows one finger to be placed into the machine at a time. The user programmes the machine for use by choosing: - the number of fingers to be varnished - the colours of the varnish to be used - the number of coatings to be applied

24 Task Description Automatic Nail Painter zThe user must get all ten fingers varnished with one coat of purple varnish. The system is already switched on when the user begins his/her task. The task is completed, when the tenth fingernail is varnished.

25 Action list Automatic Nail Painter zSystem: System displays ‘How many fingers do you want to varnish?’ User action: user selects number 10 by pressing the + or the - button until the appropriate number is shown System: System responds by displaying the current number of fingers selected to be varnished. User action: User presses ok when the correct number has been displayed

26 Action list Automatic Nail Painter (cont.) zSystem: System displays ‘choose the colour of varnish you wish to apply.’ User action: User must select the colour purple by choosing from the colour menu. This includes scrolling up and down until s/he finds purple. S/he then has to press the OK button. System: Systems displays ‘how many coats do you want to apply?’ User action: User selects the number of coats by pressing the ‘+’ or ‘-’ button until the 1 is shown.

27 Action list Automatic Nail Painter (cont.) zSystem: System displays the number of fingers to be varnished, the colour of the varnish and the number of coats to be applied. System asks for confirmation User action: User presses OK to confirm System: System displays ‘Press start to begin varnishing.’ User action: User presses start button etc.

28 Step 1- Question 1 Automatic Nail Painter zFrom the action list: Step 1 System: System displays ‘How many fingers do you want to varnish? ’ User action: user selects number 10 by pressing the + or the - button until the appropriate number is shown zQuestion 1: Is the goal clear at this stage? Not completely. The user is asked to state the number of fingers to be varnished. He could be thinking that the system deals with one hand at a time.

29 Step 1 - Questions 2, 3, and 4 Automatic Nail Painter zQuestion 2: Is the appropriate action obvious? No. The system dos neither indicate that the user has to use the ‘+’ and ‘-’ buttons nor explain their use. zQuestion 3: Is it clear that this action leads to the goal? Yes If the user presses the ‘+’ and ’-’ button the numbers are clearly displayed. zQuestion 4: zWhat problems are there in performing the action? The action is simple to perform once the user has discovered the use of the buttons.

30 Step 2 – Question 1 Automatic Nailpainter z?z?