Course Information: Human-Computer Interaction
Course Information: Human-Computer Interaction
Course Information: Human-Computer Interaction
BOOK
Human-Computer Interaction, Third Edition, by Alan Dix, Janet
Finlay, Gregory Abowd, and Russell Beale. Prentice Hall.
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Lecture Contents
Introduction
Human
Input/Output Channels
Human Memory
Thinking
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User Interface – Hall of Shame
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User Interface – Hall of Shame
Presents a number of templates
Prints custom award certificates
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User Interface – Hall of Shame
Why isn’t it usable?
Long help message for a simple ‘selection’ task
Because the interface is bizzare
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The Interface Redesigned
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The Error Dialog
We see it all the time
What’s good about the design
of this error box?
The user knows there is an error
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What is HCI
Human–computer interaction (HCI) is the study of interaction
between people (users) and computers.
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Interfaces in the Real World
Not just computers!
VCR
ATM
Phone
Copier
Car
Plane cockpit
……..
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Why HCI is important
HCI is not just ‘how big should I make buttons’ or ‘how
to layout menu choices’
It can affect:
Effectiveness
Productivity
Morale
Safety
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The Human
User – Information Processing System
Information
Comes in (Input)
Is stored (Memory)
Is processed (Processing)
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The Human
Information i/o …
visual, auditory, haptic (touch), movement
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Lecture Contents
Introduction
Human
Input/Output Channels
Human Memory
Thinking
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Input/Output Channels
Input – Output
Person interacts with outside world through information being
received and sent
Human
Input : Senses
Output: Effectors
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Input/Output Channels
Input – Five senses
Sight/Vision
Hearing
Touch
Taste
Smell
Output – Effectors
Limbs
Fingers (primary role, typing or mouse control)
Eyes
Head & Body
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Example
Computer with keyboard and mouse
Application: GUI, Menus & Icons
Information Received
Sight
Ears?
Touch?
Information Sent
Hands: Keyboard, mouse
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Vision
Vision is primary source of information for humans
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The Eye
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The Eye – Physical Reception
Eye is a mechanism for receiving light and transforming
it into electrical energy
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Interpreting the Signal
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Interpreting the Signal
Size and depth
Familiar objects perceived
as constant size
Size constancy: an object
appears to maintain a constant
size even though its retinal
image size changes with
distance
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Interpreting the Signal
Brightness
Reaction to levels of light
Affected by luminance of object
Contrast: luminance of object & its background
Colour
Made up of hue, saturation, value
Cones sensitive to colour wavelengths
Red, Green, Blue
8% males and 1% females colour blind
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Interpreting the Signal - Colour
Hue
Hue is what most people think of when we say color
Hue is the name of a distinct color of the spectrum, It is the particular
wavelength frequency
Saturation
Saturation is the purity of a colour
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Interpreting the Signal - Colour
HSV
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Interpreting the Signal
Ambiguity
B or 13 ???
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Interpreting the Signal
Optical Illusions
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Reading
Several stages:
Visual pattern of a word perceived
Decoded using internal representation of language
Interpreted using knowledge of syntax, semantics
Regression
Forwards & Backward movements of eye over text
Reading speed
Legibility: font size, line length etc.
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Hearing
Provides information about environment:
Distances, directions, objects etc.
Physical apparatus:
Outer ear
Middle ear
Inner ear
Sound
Pitch – Sound frequency
Loudness – Amplitude
Timbre – Type or quality
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Hearing
Humans can hear frequencies from 20Hz to 15kHz
background noise
phenomenon
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Touch
Provides important feedback about environment
May be key sense for someone who is visually
impaired
Stimulus received via receptors in the skin:
Thermoreceptors – heat and cold
Nociceptors – pain
Mechanoreceptors – pressure
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Movement
Fitt’s Law
Describes the time taken to hit a screen target
Index of Difficulty
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Movement
Fitt’s Law
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Movement
Pie-chart shaped menus
All options are equidistant (As opposed to lists)
Increased used of screen estate
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Today’s Interface Hall of Shame
Where does it come from?
Microsoft Word
Problem?
Four pairs of mutually exclusive options
Check boxes?
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Today’s Interface Hall of Shame
Software Automate Pro
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Today’s Interface Hall of Fame
Useful solution to a very common problem
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Lecture Contents
Introduction
Human
Input/Output Channels
Human Memory
Thinking
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Human Memory
There are three types of memory functions
Sensory Memory
Short-term or working memory
Long-term memory
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Human Memory
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Sensory Memory
Buffers for stimuli received through senses
Iconic memory: visual stimuli
Echoic memory: aural stimuli
Haptic memory: tactile stimuli
Continuously overwritten
From Sensory to Working memory
Attention: Concentration of mind on one out of a number of
competing stimuli or thoughts
Example: Cocktail party phenomenon
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Short Term Memory
Temporary recall of information
Reading a sentence, Performing an arithmetic operation etc.
Rapid access
Rapid decay
Limited capacity: 7± 2 chunks
Examples
212348278493202
Pattern Abstraction
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Short Term Memory
Closure
Desire to complete or close the task in short term memory
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Short Term Memory
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Long Term Memory
Repository for all our knowledge
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Long Term Memory
How to …..
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Reading Assignment
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Long Term Memory - Processes
Storage
Forgetting
Retrieval
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Long Term Memory - Storage
Rehearsal
Information moves from STM to LTM
Boat, Tree, Cat, Child, Gun, Plate, Home, Table, Computer, Spoon
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Long Term Memory - Forgetting
Decay
Information is lost gradually but very slowly
Interference
New information replaces old: retroactive interference
Recalling older telephone number
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Long Term Memory - Retrieval
Recall
Act of reproducing a specific incident, fact or other item (from long term
memory)
Recognition
Information provided gives knowledge/cue that it has been seen before
People are more likely to recognize a suspect in a police line-up than to provide
an accurate description from recall memory
It is easier to answer multiple-choice questions than essay questions because
the correct answer may be recognized
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Lecture Contents
Introduction
Human
Input/Output Channels
Human Memory
Thinking
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o Thinking
o Reasoning
o Problem Solving
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Reasoning
Use the knowledge we have to draw conclusion or
infer something new about the domain of interest
Deductive Reasoning
Inductive Reasoning
Abductive Reasoning
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Deductive Reasoning
Deduction:
Derive logically necessary conclusion from given premises
e.g. If it is Friday then she will go to work
It is Friday
Therefore she will go to work.
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Deductive Reasoning
When truth and logical validity clash …
e.g. Some people are babies
Correct?
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Inductive Reasoning
Induction
Generalize from cases seen to cases unseen
e.g. All elephants we have seen have trunks
therefore all elephants have trunks
Unreliable
Can never prove it true
… but useful!
Humans not good at using negative evidence
e.g. Wason's cards.
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Inductive Reasoning
Wason’s Cards
7 E 4 K
If a card has a vowel on one side it has an even number on the other
Is this true?
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Inductive Reasoning
Wason’s Cards
Common Responses
Select E & 4: Positive Evidence
Check Negative Evidences
Select E & 7
7 E 4 K
If a card has a vowel on one side it has an even number on the other
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Abductive Reasoning
Unreliable
May lead to false explanations
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Problem Solving
Reasoning: Inferring new information from what is known
Problem Solving: Finding solution to unfamiliar task using
knowledge
Several theories
Gestalt theory, Problem space theory
Analogy
Mapping: Using knowledge of similar problems/domains
Skill Acquisition
Driver, Player, Surgeon
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Errors and Mental Models
Two Types of Errors
Mistakes
Errors in choosing an objective or specifying a method of achieving it
Causes: Incorrect understanding
Humans create mental models to explain behaviour
If the model is wrong (different from actual system) errors can occur
Slips
Errors in carrying out an intended method for reaching an objective
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Emotion
Implications for Interface Design
Stress will increase the difficulty of problem
solving
shortcomings in design
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Emotion
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Individual Differences
Long term
Gender, physical and intellectual abilities
Short term
Effect of stress or fatigue
Changing
Age
Ask yourself
Will design decision exclude section of
user population?
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Humans as information processors
Input from environment (I/O)
Store, manipulate and use information and reacting
Information received through senses
Stored in Memory (Short Term / Long Term)
Use memory in reasoning and problem solving
Recurrent familiar situations allow people to acquire skills in
particular domain
Can be error when changed.
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References
Human Computer Interaction by Dix et al.
User Interface Design and
Implementation, Prof. Robert Miller - MIT
User Interface Hall of Fame/Shame
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