Transcript Document

Human Computer Interaction
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Study and design of user interfaces and interaction
British Computer Society ~“to stress the good design,
documentation and usability”
HCI approach – iterative development with focus on
user testing at an early stage
HCI is applied engineering with contribution from
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Cognitive Psychology
Cognitive Science and Engineering
Computer Science
Ergonomics
Artificial Intelligence
Graphics and Industrial Design
Engineering generally
Sociology, Anthropology and Philosophy
Human Computer Interaction
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HCI is not about ‘looking good’ or ‘making thing pretty’
– It is about making software work for user
 Good HCI does not grow on trees it has to be
cultivated
 Owning an aeroplane does not make you a pilot
REALITY
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Many systems are difficult to use but people are
adaptable
There may be conflict between safety and efficiency
Which garage do you prefer – the one which offers you
coffee, but does not fix your car, or the one with gruff
mechanics who are honest and know their stuff???
Human Computer Interaction
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Selection and design of devices – screen,
keyboard, printer, etc.
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Selection and design of interaction styles
Selection and development of tools and methods
Design of the environment where a computer is used
The tasks to be carried out using a computer
Organizational impact of a computer system
The training requirements – initial and continuing
The design of support material, manuals, on-line
helps, etc.
The attitudes and expectations of users
Safety issues
Human Computer Interaction
~ Human Factors Design Issues
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The need for consistency
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Dialogue Design
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One of the common causes of problems
with computer based systems
When interacting with a system a dialogue
is in progress between the system and the
user – this has to be planned, scripted or
choreographed
System Feedback
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Lack of suitable feedback causes feelings of
discomfort and encourages errors, e.g.
pressing RETURN too many times until the
response is seen
Human Computer Interaction
~ Human Factors Design Issues
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Amount of Feedback
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Tendency to squeeze too much on to screen
and to show more than is necessary for the
current task
Appropriate pacing
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Too slow – causes frustration
Too fast – causes pressure to perform
Human Computer Interaction
~ The Problems
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Mismatch between user and computer
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Often the user has to adapt to the computer
Terminology that of computer instead of
user
Computer function rather than task oriented
Physical limitations
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Height
Reach
Eyesight
Sensitivity to lighting condition
Human Computer Interaction
~ The Problems
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Human information processing
limitations
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Short term memory limitation
Attention highly selective and narrow
Long term memory very unreliable
Recognition easier than recall
Over learning for frequent tasks
Reasoning frequently illogical
Judgements subject to biases
Affected by fatigue and emotion
Human Computer Interaction
~ The Problem
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Resistance to Change
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How is change managed?
Who is involved?
Technology is search of a solution
Disruption of existing social order
Building for whom?
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Designer build for themselves
Poor understanding of users, tasks,
organizations
Poorly specified problems
Poorly realized solutions
HCI Issues for
Multimedia Design
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looking at how issues in HCI, humanfactors engineering, user-centered design,
can influence multimedia design
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use of different media types
MM design for vision, hearing, cognition,
memory,attention
MM design guidelines
design issues for static and dynamic media
educational MM
Types of Usability
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For multimedia, usability has three viewpoints
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Functional usability
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How easy a product is to use
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Information delivery
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how well does the product deliver the message
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GUIs, menus, interaction
prime concern
“multi media “
just because you present the material in a different way doesn’t
mean that it will be delivered better
Learnt content
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how well does someone learn the content delivered by the
product
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more applicable to educational multimedia but still considered for
movie-style presentations
Essential Issues
of Multimedia
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with MM you have more ways to present
information
should be more attractive than standard text
and still images
however potential for even bigger ‘mess’
should be about:
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delivering information in a novel way
enhancing interaction by different techniques
Multimedia ISO
Standard Terms
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message
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medium
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the content of communication between a sender
and received.
the means by which that content is delivered (how
the message is represented rather than the
technology).
modality
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the way a message is perceived by a person (e.g.
vision, hearing, touch). Note that this is not
technology based but human attributes.
Dynamic Media
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•considerations:
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how can the media be controlled over time?
can the speed of presentation be change?
what controls exist over the presentation?
how can the media format be changed?
can the image be expanded (zoom)
can the sound be filtered (amplitude, frequency)?
can components of the dynamic media
addressable directly or indirectly?
What you should remember about
dynamic media
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dynamic media tend to dominate by attracting
attention from static media
dynamic media can easily overload human
information processing
retention of detail from dynamic media is poor
co-ordination of information presented
must allow user control over dynamic media
Static Media
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considerations:
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how can the display be controlled?
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how can the media format be changed?
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standard GUI controls, eg sliders (too much text for
window and therefore need to scroll down) etc
depends on the storage format eg text changed in size
(point), and shape (font,bold)
are sub-components of medium addressable?
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idea of clickable maps where certain aspects of the
image can have different features
What you should bear in mind
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visual images tend to dominate over text
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many different messages can be extracted from one
image.
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images can be scanned quickly (quick look over)whereas reading is more
attention demanding,therefore people will be drawn towards the easier of
the two media.
interpretation of the message in an image depends on the user’s attention
and knowledge of contents.
extraction of information from diagrams requires learning the semantics of a
symbolic language
memory of image detail is generally poor unless peoples attention has been
drawn to specific facts in the image
• reading is a sequential process.
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good sentence structure and layout helps reading
memory for detail in text generally better that for image, although only the
higher order structure will be recalled accurately
Implications of the
eye on MM design
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do not expect people to attend to detail in several
different areas of an image at once.
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in MM systems only one image should be presented
at once.
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People will scan around the image, briefly focusing on
different objects, but only one at a time.
Users can not attend to still images and video at the same
time.
movement is a highly effective means of alerting the
peripheral vision and drawing the user’s attention.
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thus change or movement should be limited to one image,
otherwise it will cause stress (due to an inability to attend to
both images)
Implications of
hearing on MM design
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only part of the auditory range is necessary for
speech.
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background noise should be reduced for effective
communication
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People tolerate poor sound unless the quality is vital
although the human ear is good as suppressing noise, we
get distracted
sound is very effective as a means of alerting and
warning.
sound is a broadcast medium
speech is interpreted by the rules of grammar
Implications of memory on MM
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minimise distraction during tasks and memorisation
beware of overloading working memory, both in terms
of quantity of information and time span of retention
input from dynamic media rapidly exceeds the
capacity of working memory and hence only the high
level gist will be retained.
working memory has to be refreshed keeping the
information available in persistent media, thus allow
to re-view test or image
structuring information (chunking)
memorisation of detail from image is limited
Implications of attention to MM
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do not use too many competing demands for
attention
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Attention tends to be diverted by change hence temporal
media such as film, animation and sound will dominate over
static media such as pictures and text
dynamic media contains change by definition and
therefore attract attention more strongly than static
change in static media (highlighting) will attract
attention
two or more dynamic media will compete for the
users attention and this can lead to stress and fatigue