1 cmt 3210: understanding the human element in hci lecture 4 models of human-computer interaction...
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CMT 3210: Understanding the human element in HCI
Lecture 4Models of human-Computer InteractionMental Models
Elke Duncker
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Evaluation and execution
Approximate model of how people carry out tasks
Emphasises carrying out actions and getting feedback
The World
Goal
Evaluation: Comparing
what happened
with what we wanted
Execution:Carrying out actions on the world
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The World
Perception
Cyclic model of human action
Seven stage process Can start anywhere
Goal
Intentionformation
Action specification
Execution
Evaluation
Interpretation
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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?
Goals World
Execution
Evaluation
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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
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
Determine the function of the device
Tell what state the system is in
How easy is it for the user to:
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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 ProcessorDetailed model of how computer users process
information Intended to help designers do predictionsConsists of specialised concurrent processing
units and memories characterised by speed, decay time, capacity,
encoding
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Model Human Processor
Working memory
Long-term memory
Auditory memory
Visual memory
Stimulus
Perception
Cognitive processo
r
Motor processo
r
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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 stagesUsers act rationally (most of the time):
Goals + Task + Operators + Inputs + Knowledge +
Processor limitsBehaviour
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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 artefactThe user’s image about the machineMaking 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
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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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-it-works-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 modelsb) feedback, hypothesis-testing (but beware
mode errors)c) manuals and help systemsd) analogy and metaphorse) designer’s conceptual model:
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How designers influence the user’s mental model
Designer’s conceptual
model
Interface design
User’s mental model
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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