Transcript COM 3210 : Understanding the human element in HCI

CMT 3210: Understanding the
human element in HCI
Lecture 4
Models of human-Computer Interaction
Mental Models
Elke Duncker
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Models of Human-Computer
Interaction
Normans 7 stage model
Human Processor model
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Evaluation and execution
 Approximate model of
how people carry out
tasks
 Emphasises carrying out
actions and getting
feedback
Goal
Execution:
Carrying out
actions on
the world
Evaluation:
Comparing
what
happened
with
what we
wanted
The World
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Cyclic model of human action
Goal
 Seven stage process
 Can start anywhere
Intention
formation
Action
specification
Evaluation
Interpretation
Execution
Perception
The World
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Gulfs of execution and
evaluation
Gulf of execution:
How does the user translate intentions into action?
Gulf of evaluation:
How does the user understand the effects of actions
and does s/he tell when her/his goals are satisfied?
Execution
Goals
Evaluation
World
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Bridging the gulfs
Execution
Mappings:
are actions designed so the user make the
connection between the effects they intend to achieve
and the actions provided by the system?
Evaluation
Feedback:
is information about the system state provided in a
way that allows users to determine whether goals are
satisfied?
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Using the model as a design
aid
How easy is it for the user to:
Determine the
function of the device
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
Tell what state the
system is in
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Principles for good design
Visibility
of the state of device and possibilities for action?
Good conceptual model
consistent presentation, coherent system image?
Good mappings
relation between actions and effects?
Feedback
about effects of actions?
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A model of human information
processing
Model Human Processor
Detailed model of how computer users process
information
Intended to help designers do predictions
Consists of specialised concurrent processing
units and memories
characterised by speed, decay time, capacity,
encoding
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Model Human Processor
Stimulus
Perception
Auditory
memory
Visual
memory
Working memory
Motor
processo
r
Cognitive
processo
r
Long-term memory
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Principles of the MHP
Perception takes time - depends on stimulus
intensity
Processing takes time - depends on task
demands, information load, practice
Different encoding used at different stages
Users act rationally (most of the time):
Goals + Task + Operators
+ Inputs + Knowledge +
Processor limits
Behaviour
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Applications in HCI
The GOMS and KLM analysis techniques
Identifies kinds of processing and memory
Identifies possible concurrency
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Comparing the models
MHP almost exclusively about what goes on
inside the head
Focus on human performance - especially time
Norman's model more about human-machine
interaction
without saying how processes are implemented or
what exists in the head
Distinguish between "in the head" and "in the world"
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Knowledge in the head and in
the world
Knowledge needed to translate intentions into
plans and actions may be
remembered by the user (in the head)
e.g. unix commands
embedded in the devices used (in the world)
e.g. direct manipulation interfaces
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Summary HCI models
Norman's 7 stage model of human action
Identifies processes involved in action
Doesn't specify how they take place
Useful as a tool for thinking and analysis
Consideration of "in the head" / "in the world"
Model Human Processor
Detailed account of human information processing
Specifies how internal processes work
Used for making predictions (e.g. GOMS)
Framework for topics that will come later
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Mental Models
A person’s image about an artefact
The user’s image about the machine
Making sense of the world from inside
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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.
Mental models are generally incomplete and
inaccurate, but serve a purpose
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Example Camera
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What are the components and how do they
fit together?
How does it work?
What causes what?
How do you use it?
How do you use your understanding when
something goes wrong?
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Example: London
Underground Map
•
•
what is it good for?
what isn’t it much use for?
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The Contents of a Model
Kieras (1982) categorised the kinds of
knowledge that people have about a device as
follows.
Label or name of the device
Function or purpose (what goals can be
accomplished)
Controls and indicators
Inputs, outputs and connections
Power sources and requirements
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Contents of a Model (cont.)
External layout and appearance
Internal layout and appearance
External behaviour (input-output function)
How to operate the device to accomplish goals
Procedures for troubleshooting and maintenance
Internal structure and mechanisms (how it works)
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Mental Models
A runnable mental model = how-it-works
knowledge + knowledge how-to-use-the-how-itworks-knowledge !
How-it-works knowledge may be at various
levels of detail.
Strategic knowledge includes various strategies
— e.g. inference, prediction, diagnosis. These
are transferable skills.
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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:
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How designers influence the
user’s mental model
Designer’s
conceptual
model
User’s mental
model
Interface
design
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Note
This view puts the designer at the centre
It 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).
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Domains and devices
 'Mental models' are about
understanding the device
[and its representation of
the domain].
 User may be:
 manipulating domain
through device, or
 investigating domain
through device
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Further Reading
For the execution-evaluation model:
Donald Norman "The Design of Everyday Things”
(also appeared as "The Psychology of Everyday
Things")
For the Model Human Processor:
Stuart Card, Thomas Moran and Alan Newell "The
Psychology of Human Computer Interaction"
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