1. CEN3722 Human Computer Interaction Knowledge and Mental Models
Dr. Ron Eaglin

2. Objectives Describe and give examples of how knowledge is represented
Describe and give examples of how knowledge is organized
Define the term “Mental Models” and describe how mental models assist in understanding systems
Be able to describe
Scripts
Schemas
Functional Mental Models
Structural Mental Models

3. Objectives Describe and give examples of the following design concepts
Visibility
Affordances
Constraints
Feedback
Transfer Effect
Natural Mappings
Population Stereotypes
Individual differences

4. Knowledge Representation
Analogical Representation
Meaning through analogy (like the wind)
Propositional Representation
Abstract language-like statements (the dog is in the house)
Distributed Representation
Knowledge is implicit in connection (between nodes)

5. Organizing Knowledge ANIMAL HAS CAN IS-A FLY WINGS BIRD HAS CAN EATS
BEAK
WALK
TWEETY
BUGS

6. Organizing Knowledge Knowledge is highly organized
Semantic Networks - organized by nodes and links
Object, Properties, and Relationships

7. Organizing Knowledge ANIMAL HAS CAN IS-A FLY WINGS BIRD HAS CAN EATS
BEAK
WALK
TWEETY
BUGS

8. CAN
FLY
AIRPLANE
IS-A
ANIMAL
CAN
HAS
IS-A
HAS
MACHINE
WINGS
BIRD
HAS
EATS
IS-A
BEAK
TWEETY
BUGS

9. Organizing Knowledge
Schemata - network of general knowledge based on previous experience
Script is an example of a schema.
Script is a schema to be followed that represents ‘how to’ knowledge (that is, procedural knowledge)
Works well if the script is appropriate and known (e.g., eating in a restaurant)
Doesn’t work well in novel situations
Allow us to carry out activities with minimum of effort
Capitalize on regularity of events and situations

10. Schema to Script - Sample
Open Application
Scan unread mail in inbox
Find important mail
Read mail
Reply to sender
Start new
Type message
Spell check
Add signature
Send
Close application

11. Mental Models
The model people have of themselves, others, the environment, and the things with which they interact’…(Norman, 1988)
Dynamically constructed by acting on stored schema
‘Running’ a mental model - the process of generating the model (e.g., visualizing building to count windows)

12. Example Form a mental model of a classroom
What elements are in your mental model?
Where did these elements come from?

14. Example – and Review of Mental Model
Your classroom might have contained desk, front area, whiteboard/blackboard, windows, doors, aisles between desks, papers
The model people have of themselves, others, the environment, and the things with which they interact’…(Norman, 1988)
Dynamically constructed by acting on stored schema
‘Running’ a mental model - the process of generating the model (e.g., visualizing building to count windows)

15. Types of Mental Models Structural model Functional model
User has internalized structure of how the object works
Internalized declarative knowledge
Explanation of the underlying mechanism
Functional model
User has internalized how to use the object
Internalized procedural knowledge
Developed from past knowledge and experience in a similar domain.

16. Bicycle Drive Train – Structural Model
Front Derailleur
Chain ring

17. Bicycle Drive Train – Functional Model
To Shift Rear Derailleur to Higher Speed - Push Right Hand Lever
To Shift Rear Derailleur to Lower Speed - Pull Right Hand Lever
To Shift Front Derailleur to Higher Speed - Push Left Hand Lever
To Shift Front Derailleur to Higher Speed - Pull Left Hand Lever

18. Mental Model The UI should match the users mental model
Challenging – mental models are often vague and incomplete
Part of UI design
Getting user mental models to follow the UI

19. Design Implications Affordances Visibility
The perceived and actual fundamental properties of the object that determine how it could possibly be used.
Shows relationships between what you want to do and what is possible.
Visibility
Make apparent what the system can and cannot be used for – this must be apparent to the user.

20. Example - Affordances
Perceived properties
Actual properties

21. Visible Affordances Slide Projector
One button: How does one forward and reverse
with one button?
More functions than controls
Remote

22. Visible Affordances How do you call forward with a standard phone?
* 9 + number
Problem
Operation is hidden
Outcome is hidden (did it work?)

23. Affordances = Visual Cues
Well-designed
Visible clues to operation
Visible clues to success of operation
Poorly Designed
No visible clues
False clues to operation

24. Constraints VISIBLE CONSTRAINTS
Limitations of the actions possible perceived from the object’s appearance
Shows what parts operate and how
Provides range of possible uses

25. Constraints

26. Transfer Effects
Prior Experience gives cues for functionality and operation
Learning – analogies – metaphors
Positive Transfer – previous learning transfers
Negative Transfer – previous learning conflicts
Examples
Typewriter and computer keyboard – same layout
Windows 7 (similar to previous) to Windows 8 (tiles)

27. Feedback
Show results of actions

28. Feedback Slow operations Greater than 1 second – need indicator
Longer operations – need % completed

30. Mapping Physical Mapping – displays and controls
Cultural Mapping – functionality and appearance

31. Physical Mapping arbitrary vs. natural

32. Cultural Mapping

33. Individual Differences
Differ by experience, interest, ability
Examples: Right vs. Left Handed
Cognitive Ability
Dexterity, eyesight, memory
Skills

34. Summary Describe and provide examples of how knowledge is represented
Describe and provide examples of how knowledge is organized
Define mental models and provide examples of mental models and how they are used.
Define and give examples of
Scripts
Schema (schemata)
Semantic Networks
Functional Mental Models
Structural Mental Models

35. Summary Describe and provide examples Visibility Affordances
Constraints
Feedback
Transfer effects
Mapping
Population stereotypes
Individual differences