Transcript chapter2

Principle of Human Computer
Interaction
Faculty of Computing and Information Technology
King Abdul Aziz University
Khalid Al-Omar
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Understanding Human, Computer,
and Interaction
Lecture 4
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the Human, Computer, Interaction
• In order to design something for someone, we need
to understand the:
1. the Humans
– perceive the world around them.
– store and process information and solve problems.
– physically manipulate objects.
2. the Computer
– Technology they going to use
3. the Interaction
– How people going to interact to technology
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the human
1. Information Input/Output Channels
–
visual, auditory, haptic, movement
2. Information stored in memory
–
sensory, short-term, long-term
1. Users share common capabilities/limitation but are
individuals with differences
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Input-Output Channels
• Five major senses: sight, hearing, touch, taste, and
smell.
Sight, hearing, and touch are the most important in HCI
• Receive information from computer
Sight
Hearing
Touch
• Send information to computer
Touch (e.g. mouse),
Sight (e.g. eyegaze system (using eyes movement))
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Input-Output Channels (continue)
1. Vision
o
o
o
Colour
Reading
Optical Illusions
2. Hearing
o
Sound
3. Touch
o
Movement
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Vision
1. Colour
Colour blind: is the decreased ability to perceive
differences between some of the colors that others can
distinguish.
8% males and 1% females colour blind
 Red–Green
 Blue– Yellow
• There are two major types of color blindness:
Total color blindness (is less common)
Partial color blindness
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Partial color blindness
Red–Green color blind
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Partial color blindness (continue)
– Blue - Yellow color blind
http://www.colblindor.com/2006/05/08/tritanopia-blue-yellow-color-blindness/
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Total color blindness
http://www.colour-blindness.com/variations/total/
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GUI & color blindness
• Graphical User Interfaces should be
understandable even without colors.
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2. Reading
• People are able to read at 200 wpm on paper,
and 180 wpm on a monitor
• Reading from computer screen is slower than from a
book.
– Longer line length
– Fewer words to a page
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Reading- lowercase/ UPPERCASE
• Also, you should know that WORDS WRITTEN IN
BLOCK CAPITALS take longer to read than those in
lower case.
• lowercase
– easy to read
• UPPERCASE
– Better for individual letters and non-words
e.g. flight numbers: BA793 vs. ba793
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3. Optical Illusions
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3. Optical Illusions
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Hearing
• Provides information about environment:
distances, directions, objects etc.
• Humans can hear frequencies from 20Hz to 15kHz
– Human ear can distinguishing frequency changes at low frequency, but
is less accurate at high frequencies.
• Auditory system filters sounds
– allowing people to ignore background noise and concentrate on
important information. for example, in party
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Hearing
• People tend to underestimate the amount of
information that they receive through their ears.
• People are selective to their hearing.
– For example, if someone says your name
• People not able to differentiate sound, If sound are
too loud or frequencies too similar
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Hearing/Sound
• Sound used as:
– warning or notification
– Sound especially used while eyes are busy
• Types of sound:
• Speech or non-speech
– For example, Non-speech like music
• Speech sound can be used convey information
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Hearing/Sound
• Non-speech sound can be used for:
1. Attention
• For example, end of a process
2. Confirmation
• For example deleting a file
3. Status information
• For example, monitoring the progress of a process
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Touch
• May be key sense for someone who is visually impaired.
• Stimulus received via receptors in the skin:
– heat and cold
– Pain and pressure
• Touch will become more important in the near future
• Touch become important in shopping online
– For example, clothes
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Movement
• Time taken to respond to stimulus:
reaction time + movement time
• Movement time dependent on age, fitness etc.
• Reaction time - dependent on stimulus type:
– visual
– auditory
– pain
~ 200ms
~ 150 ms
~ 700ms
• Increasing reaction time decreases accuracy in the unskilled
user but not in the skilled user.
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Information stored in memory
There are three types of memory function:
Environment input
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Sensory memory
• Buffers for stimuli received through senses
– Iconic memory: visual stimuli
– Echoic memory: aural stimuli
– Haptic memory: tactile stimuli
• Sensory memory continuously overwritten by new
information
• Information is passed to short-memory by attention
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Short-term memory (STM)
– Rapid access ~ 70ms
– Forgetting occur ~ 200ms
– limited capacity: the number of objects and chunks of new
information an average human can hold in short memory.
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Short-term memory (STM)
– capacity limits can be overcome by
1. Grouping of information into larger meaningful units
2. Individual differences, e.g., chess masters vs. novices
3. Also seen in everyday tasks that must be held in STM
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Examples
212348278493202
0121 414 2626
HEC ATR ANU PTH ETR EET
‘The cat ran up the tree’
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Long-term memory (LTM)
• Stored all our knowledge
• Slow access ~ 1/10 second
• Forgetting occur more slowly
• Huge or unlimited capacity
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LTM - Storage of information
• How does information get into LTM?
– Rehearsal: information moves from STM to LTM
• total time hypothesis
– Learning amount = Learning time
• Learning time is most effective if it is distributed over time
– optimized by spreading learning over time
• structure, meaning and familiarity
– information easier to remember
• For example, password should be meaningful to you
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Errors and mental models
Types of error
• slips
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right intention, but failed to do it right
causes: poor physical skill,inattention etc.
change to aspect of skilled behaviour can cause slip
• mistakes
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wrong intention
cause: incorrect understanding
humans create mental models to explain behaviour.
if wrong (different from actual system) errors can occur
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Emotion (cont.)
• emotion influences how we respond to situations
– positive  creative problem solving
– negative  narrow thinking
“Negative affect can make it harder to do even
easy tasks; positive affect can make it easier to
do difficult tasks”
(Donald Norman)
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Individual differences
• long term
– Gender, physical and intellectual abilities
• short term
– effect of stress
• Changing through time
– age
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