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Human Aspects:
The user is considered as an information
processing system herself/himself
The term Cognition includes understanding,
remembering, reasoning, attending, being
aware, acquiring skills and creating ideas.
Cognition plays an important role in Human
Computer Interaction (HCI).
Cognitive Processes in HCI:
Users give input to the computer by motor
control (e.g. finger movements for pressing
keys and moving the mouse), and output is
typically provided through the screen, where
the effects of providing input to the system
are observed.
recently: multimedia, handheld devices,
voice and virtual reality rather than classical
keyboard-mouse-screen environment.
Human Vision:
Highly complex system.
Primary source of information for most
people.
Raw image might not be the perceived
image, because vision is often influenced by
expectations about a visual scene and
therefore interpretations of the visual scene.
Human Vision:
Pictures by Fultz
Human Vision:
Pictures by Fultz
Human Vision:
Perception and
Representation:
Constructivist and Ecological Approaches:
Both argue that humans are active
perceivers, but there are important
differences in terms of the way these
approaches explain perception.
Constructivist Approaches:
Suggestion that people perceive actively by
elaborating retinal images.
Perception involves intervention of
subjective representations and memories.
Prior knowledge and experiences play a role
in perceiving scenes (G. Sommerhoff: “We
see what we expect to see”)
Organising Principles
Perception of patterns as meaningful wholes
defined by:
• Proximity
• Similarity
• Closure
• Continuity
• Symmetry
Ecological Approaches:
People actively explore environment (seeing,
smelling, hearing, tasting and touching).
But different from Constructivist Approaches in
that Ecological Approaches do not assume
processes of elaboration that are based on
prior knowledge (though they do not deny that
prior knowledge is necessary).
Ecological Approaches try to explain how
people deal with continuous events over time.
These approaches ask what we need to know
about our environment to carry out particular
activities (e.g. finding a particular website with
Google).
Users will actively try to find the necessary
information by applying the knowledge they
have to find the answer.
Ecological approaches have been highly
influential for theoretical accounts in user
interface design.
In User Interface Design, Visual perception is
currently seen as the most important way to
interact with the environment, followed by voice
and hearing (e.g. in Speech Recognition of
human voices and in the design of
computerised voices) and haptic perception
(e.g. touch in Virtual Reality Applications).
Speed and accuracy of movement play an
important role, e.g. where on the screen to
display particular icons so that they can be seen
and reached easily.
The most-used icons should be the best visible
and the easiest ones to reach (e.g. by mouse,
with touchscreen etc.).
The other two senses, i.e. the smelling and
tasting senses are not important in user
interface design (at least so far).
Data Graphics
Graphics can be instruments for reasoning
about quantitative information (Tufte, 1983).
Well designed data graphics are typically the
ones that are simplest to understand and
express complex information in a clear way.
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Column/Bar Charts or Histograms
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Stacked or Segmented Columns/Bars
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Pie Charts
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Start, Circular, Pattern or Radar Charts
Problems with Charts
The variety of graphic techniques offered does
not guarantee that they will be effectively
applied.
A chart for a high resolution colour screen may
be reproduced in black and white when
printed and therefore difficult to understand.
For example, pie charts cannot order numbers
along a visual dimension.
Attention and Memory
Constraints:
3 different types of memory functions:
1. Sensory buffers
2. Short-term Memory = Working Memory
3. Long-term Memory.
Sensory Buffers
Exist for each sensory channel that is important
in relation to User Interface Design:
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iconic memory for visual stimuli
echoic memory for aural stimuli
haptic memory for touch
Sensory Buffers (continued)
Sensoric Buffers are constantly overwritten by
new information coming from these
channels.
Sensoric Buffers are extremely short-term:
0.5 seconds for visual stimuli.
Not possible to give seconds for sounds,
because they are received at different times.
Sensory Buffers (continued)
Very brief play back of acoustic sounds is
available to the Echoic Memory.
Short-term/Working Memory
Acts as a scratch pad for the temporary recall of
information.
Is the working area where information is
temporarily stored to be further processed
for the following purposes:
handling incoming information, selecting,
retrieving, planning, storing, preparing
outputs and actions.
Short-term/Working Memory
continued
Capacity is limited in amount and time.
On average, the number of chunks we can
remember is 7 (Magical Number 72, first
reported by Miller, 1956).
Chunk = digits, names, letters, other concepts
Relation between Sensory
Buffer and Short-term
Memory
Information is passed from sensory buffer to
Short-term memory.
This happens through Attention.
Attention = Mind concentrating on one or few of
several competing stimuli or thoughts.
Relation between Sensory
Buffer and Short-term
Memory continued
Attention thus acts as a filter for stimuli that
compete at a particular time.
People are able to focus their attention
selectively, e.g. Cocktail Party phenomenon.
How can we apply this
knowledge to User Interface
Design
If the probability that people get distracted is
high, how can we get their attention back?
How do we get people‘s attention to focus on
the aspects they need to be looking at or
listening to in order to do the task
successfully?
How can we apply this
knowledge to User Interface
Design
How can we guide people‘s attention to the
relevant information on the display?
Long-term Memory
Storage of facts, life experiences and
procedures that are typically successful when
performing a particular task. It also includes
general knowledge.
Information gets into the Long-term memory
through Short-term=Working Memory after it
has resided there for a couple of seconds.
Long-term Memory
continued
2 types: Episodic and Semantic Memory
Episodic Memory represents our memory of
events that occurred in our lives, i.e.
experiences we have made.
Episodic Memory stores these experiences in
a serial form.
Long-term Memory
continued
Episodic Memory lets us construct the events
that took place at certain points of our lives.
Examples of Episodic Memory are:
One’s personal memory of learning how to ride
a bike for the first time.
One’s first kiss.
One’s graduation, etc.
Long-term Memory
continued
Semantic Memory stores facts, concepts and
skills that we have acquired.
For example:
One’s knowledge of how to use UNIX.
One’s skill knowledge of how to ride a bike.
One’s knowledge of London’s population size.
Long-term Memory
continued
Episodic and Semantic Memory are related
towards some extent.
Information in Semantic Memory is derived
from Episodic Memory, because our personal
experiences can support us in learning new
facts and concepts.
Long-term Memory
continued
The Structure in Semantic Memory allows to
access information, to represent relationships
between pieces of information and may suffer
from interference between different pieces of
information.
Long-term Memory
continued
3 Main properties of Long-term Memory:
1. Storage/Memory of Information
2. Forgetting
3. Information Retrieval
Relation between Shortterm and Long-term Memory
Information from Short-term/Working Memory is
transmitted to Long-term Memory through
rehearsal.
However, information must be meaningful,
because repetition alone is not enough for
information to be successfully transmitted into
Long-term memory.
Relation between Shortterm and Long-term Memory
continued
Meaningful information can be related to
already existing structures in Long-term
Memory, which makes it easier to remember.
This is important in relation to User Interface
Design. It is good to design applications that
can be related to already existing structures.
Forgetting
Two main theories (Dix et al. 1993):
1. Decay (information decays with time)
2. Interference (information is not accessible
due to interference between competing
information. New information causes loss of old
information, but the cause of loss is not time
itself)
Meaningful Interfaces
Learning and Memory play an important role in
the design of meaningful interfaces.
The specific memory processes that play a role
are:
1. Recall
2. Recognition
Recall and Recognition
Recall: Information is reproduced from memory,
e.g. if you learn a list of words and are later
asked to reproduce the list of words.
Recognition: Memorised information is not
reproduced, but must be chosen out of a list of
possible alternatives, e.g. if you learn a list of
words and are later asked to tick the words you
have experienced during the learning phase on
a list that also includes other words.
Recall and Recognition continued
The decay of learnt information is much larger
under Recall conditions.
Under Recognition conditions, there is much
less decay: long-term recognition after a couple
of minutes is often similar to that after hours or
days.
How can the findings about Recall
and Recognition be applied to
User Interface Design?
It is well-known that people recognise material
far easier than they recall material.
Reduction of interfaces that rely on the recall of
information, e.g. sequences of commands.
How can the findings about Recall
and Recognition be applied to
User Interface Design?
continued
Instead: Interfaces where users have the ability
to recognise the necessary information, e.g.
graphical user interfaces in Windows instead of
written commands in MS-DOS.
This way users do not have to remember
sequences of commands.
Other Aspects of Meaningful
Interfaces
In general, meaningfulness of a stimulus or
concept is determined by their familiarity and
associated imagery.
Meaningfulness determines the extent to which
new material can be remembered.
Other Aspects of Meaningful
Interfaces continued
Specifically related to User Interface Design,
the perceived meaningfulness of icons
appearing on visual display depends on:
1. Context in which icon is used
2. The task for which icon is used
3. The design (surface form) of icon
4. The type of underlying concept that is
represented.
Other Aspects of Meaningful
Interfaces continued
Specifically related to User Interface Design,
the command names are also important to
consider.
It is useful to consider the characteristics of the
potential users, the context in which the
interface is likely to be applied and the cultural
characteristics of the group that is using the
commands to prevent misunderstandings.
Other Aspects of Meaningful
Interfaces continued
Specifically related to User Interface Design,
there are additional techniques to highlight
attention.
• Making use of spatial and temporal cues, e.g.
incorporate animations.
• Making use of colour or different shades.
• Flashing, reverse video and acoustic
information.
• Provide systematic information about the
status of activity (what is currently done and
what still needs to be done - you often see this
when installing a program and you need to
press next repeatedly.
• Ideally, the system should let people return to
the point where they interrupt a particular task if
they need to interrupt the process and want to
return later without repeating the whole
process.
• Routine tasks that are likely to be forgotten
should be brought to the user’s attention, e.g.
by prompting the user whether s/he wants to
save the file.
Focusing attention
at the interface
• Urgent and important information (e.g.
warning messages) should be placed at the
best visible place.
• Less urgent information should be placed at
specific areas of the screen (this particular
area should be used consistently so that the
user always knows where s/he can find this
type of information).
Focusing attention
at the interface continued
• Rarely needed information should not be
placed in the screen area (e.g. help options),
but they should be easy to reach (e.g. through
the menu).
• A good interaction design places a high
weight on consistency, e.g. changes should be
as limited as possible from one screen display
to the next.
Focusing attention
at the interface continued
• Consistency also applies to buttons, words to
describe specific terms and icons, which
should always appear on the same location
and which should always have the same
shape and size.
• Try to assess how much information is
needed to make the application as simple as
possible, and avoid to include any
unnecessary information.
Focusing attention
at the interface continued
• By trying to simplify, the following guidelines
may help:
1. Use concise wording of instructions,
messages and other text.
2. Use icons that are simple to recognise and
that tell as much as possible about the
application.
Focusing attention
at the interface continued
• By trying to simplify, the following guidelines
may help:
3. Minimise the overall density on the screen.
4. Minimise the local density in particular areas
of the screen, e.g. avoid having too much
information at the top or bottom, left or right.
Focusing attention
at the interface continued
• By trying to simplify, the following guidelines
may help:
5. Use plenty of white (empty) space around
text so that it is better visible.
6. Try to maintain a logical structure on the
screen by placing things that belong to each
other near each other.
Focusing attention
at the interface continued
All these guidelines are important for user
interfaces with the classical keyboard, mouse
and screen environment.
However, they become even more important
for handheld devices, where size of the visual
display is very limited.