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

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

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

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)

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

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

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

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

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

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

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)

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

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)

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.

Bicycle Drive Train – Structural Model Front Derailleur Chain ring

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

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

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.

Example - Affordances Perceived properties Actual properties

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

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

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

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

Constraints

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)

Feedback Show results of actions

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

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

Physical Mapping arbitrary vs. natural

Cultural Mapping

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

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

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