Mental Models, Metaphors, Errors

Question 1

Mental Model

Answer 1

“If the organism carries a small-scale model of external reality and of its own possible actions within its head, it is able to try out various alternatives, conclude which is the best of them…[and] utilize the knowledge of the past events in dealing with present and the future

Question 2

Mental Models 2

Answer 2

• A mental model is an internal representation that we form in our mind of how something works
• A mental model explains how a system works
• We use mental models to make predictions of how a system will reach when we interact with it
• Our mental model of a system can be different from how the system actually works
• Mental models can be functional (know what to do, but not why) or structural (know what to do and why)

Question 3

Example: Heating

Answer 3

• It’s winter and you come home, and it is cold in your room, only 15 °C.
• You want a cozy room temperature of 20°C,
  as quickly as possible.
• What do you do?
• Strategy 1: set the thermostat to 20°C and wait
• Strategy 2: set the thermostat to max (=30°) and turn down to 20° once it is warm?

Question 4

Acquiring mental models

Answer 4

• Mental models can be learned from explanation
  
  • Somebody can teach us how something work
  • Tutorials, instructions
• Mental models can be formed from experience
  
  • Interaction with the system and observing what happens
  • Forming a model that is consistent with the observed behaviour
  • Often based on physical analogies and metaphors
  • Can be incomplete
  • Can be incorrect

Question 5

Characteristics of Mental Models

Answer 5

• ” A mental model is what the user believes about the system at hand” (Jakob Nielsen)
  
  • A mental model is based on belief, not facts
  • It’s a model of what users know (or think they know) about a system
• Mental models are not perfect
  
  • Incomplete – users will understand some parts better than others
  • Inertia – once learned, users will stick to their model, and not easily adapt
  • Unscientific – models reflect superstitious behaviour

Question 6

Designers’ and Users’ Models

Answer 6

“One of usability’s big dilemmas is the common gap between designers’ and users’ mental models” (Jakob Nielsen)

• Individual people each have their own mental model
• Designers form wonderful mental models of their own creations
  
  • Leading them to believe that each feature is easy to understand
• Users’ mental models of the user interface are often more deficient
  
  • Making it more likely for users to make mistakes
  • Users often find the user interface much more difficult to use

Question 7

Mental Models - Key Points

Answer 7

• Users form mental models of how a system works, through their interactions with the system
• Users plan their actions based on what their mental models predicts about the appropriate course of action
• If the system behaves as predicted by the user’s mental model, then it will appear logical
• If it does not behave as predicted, it will appear confusing
• If their interaction leads users to form flawed models, users will likely make more errors

Question 8

Conceptual models

Answer 8

• A conceptual model is a high-level description of how a system is organized and how it operates
• Conceptual models are created by designers, to provide users with everything they need to know, to be able to use the system
• Abstracting from system detail the user does not need to know about
• Focusing on aspects of the system the user needs to understand for their interaction with
• User interfaces are designed to convey the conceptual model to the user

Question 9

Different Models of a System

Answer 9

• The UI communicates the CM to the user
• Hiding other system aspects (transparency)
• Through interaction, users form a MM
• Ideally the MM is consistent with the CM

Question 10

Conceptual models 2

Answer 10

• How can a user interface communicate a conceptual model?
• User interfaces describe the concepts and actions that users need to know to be able to interact with an application, device or system
• To make it easy for users to learn how to use a new system or interface, conceptual models are designed to draw on users’ previous knowledge
  
  • Metaphors: using concepts that are familiar from other domains
  • Mappings: showing the user how actions relate to effects, based on familiar analogies

Question 11

Metaphors

Answer 11

• Metaphors take concepts from one domain and apply them to another
  
  • they help users form a mental model in new domain
• User can draw on their knowledge from another domain and apply it to reason about how a new system works
• Metaphors are used pervasively in computer systems, and become so familiar that we forget that they were adopted from other domains
  
  • Files and folders
  • Copy, cut, paste
  • Cursor

Question 12

Desktop metaphor

Answer 12

“if a new user wants to understand about how the computer file system works, he need only think about how an office filing cabinet works and then carry over this same way of thinking to the computer file system”

Question 13

Mappings

Answer 13

• Mappings help users build a mental model of how actions relate to effects
• Mappings are an important design principle that we do not notice when it is well applied

-Good mappings are:
- Understood immediately (mental model is instantly clear)
- Consistent with knowledge the user already has
- No effort to remember

Question 14

Natural Mappings

Answer 14

• Many mappings feel natural because they are based on analogies
• Spatial analogies
  
  • e.g., elevator controls ordered from top to bottom
• Metaphorical analogies
  
  • e.g., rising levels (volume, temperature, etc) associated with going up (as in water levels rising)
• Cultural analogies and standards
  
  • e.g., water taps in UK: left is for cold, right is warm

Question 15

Historical analogies and metaphors

Answer 15

Question 16

Natural Mappings 2

Answer 16

• Stimulus-Response compatibility
  
  • Degree to which the physical arrangement of the stimuli matches the location of the expected responses
• Natural mappings
  
  • Design in which the system’s controls represent or correspond to the desired outcome
  • When controls map to the actions that will result, systems are faster to learn and easier to remember
  • Bridging gulf of execution

Question 17

Metaphors and Mappings - Key Points

Answer 17

• A conceptual model is what a designer designs as the model they want the user to acquire
• Designers aim to communicate the conceptual model through the design of the user interface
• Metaphors are useful as they help users transfer knowledge from other domains to a new interface or system
• Mappings help users build a mental model of their actions relate to desired outcomes
• Mappings build on analogies and standards

Question 18

What are Errors?

Answer 18

• Error: any situation in which an action sequence does not lead to the intended result
• An error can occur for two reasons:
• An error in planning that results in wrong choice of action
  
  • Misinterpretation of available actions, or
  • Applying an incorrect mental model
• An error in the execution that results in an unintended action sequence
  
  • “I didn’t want to do that”

Question 19

Types of Error

Answer 19

Question 20

Error prevention - Mistakes

Answer 20

• What can we do to prevent errors?
• Avoiding conscious mistakes
  
  • Provide a clear conceptual model
  • Familiar concepts and metaphors, for user to know what to do
  • Consistency with other systems, for users apply learned procedures
  • Good mappings, for users to correctly associate actions with outcomes

Question 21

Error prevention- Slips and Lapses

Answer 21

• Preventing slips
  
  • Improve ergonomics of the interface
  • Make click targets bigger and put enough space between them
  • Use constraints to prevent entry of invalid data
  • Use forgiving formatting
  • Provide good defaults
• Preventing lapses

Question 22

Error prevention- Slips and Lapses

Answer 22

• Preventing slips
  
  • Improve ergonomics of the interface
  • Make click targets bigger and put enough space between them
  • Use constraints to prevent entry of invalid data
  • Use forgiving formatting
  • Provide good defaults
• Preventing lapses
  
  • Keep track for the user, and remind them of what still needs doing
  • Design interactions so there is nothing users need to do after they reached their primary goal

Question 23

Errors - Key Points

Answer 23

• “If an error is possible, someone will make it” (D. Norman)
• Mistakes happen, when users have the wrong mental model
  
  • Choosing the wrong plan of action for what they aim to achieve
• Slips happen when users have the right plan of action but do not execute it as they had intended
• Lapses happen when users forget to execute a step in their plan
• Mistakes, slips and lapses all point to different usability problems, and there are different strategies to avoid them