Transcript Short-term Memory

HCI
Cognitive Frameworks for HCI
“Doing Work” View
• Need to understand the user and human
behavior
• How does an architect approach a
custom home design for a new client?
Fall 2011
the human
the human
• Information i/o …
- visual, auditory, haptic, movement
• Information stored in memory
- sensory, short-term, long-term
• Information processed and applied
- reasoning, problem solving, skill, error
• Each person is different
Modeling Humans
• For HCI, goals are primarily in
“Computer” and “Interaction”
- Utility of human model lies in how well it
helps with interfaces
• Card, Moran, and Newell (1983)
Model Human Processor
- “Classic” example of cognitive
architecture with focus on humans
interacting with computers
- Each has own processor and memory
Cognitive models
They model aspects of user:
understanding
knowledge
intentions
processing
Common categorization:
Competence
Performance
Computational flavor
No clear divide
Utah School of Computing
Student Name Server
slide 6
Model Human Processor - Original
The Model Human Processor
The model human processor consists of three interacting
systems. Each has its own memory and processor.
Perceptual processor
• Outputs into audio storage
• Outputs into visual storage
Cognitive processor
• Outputs into working memory.
• Has access to:
Working memory
Long term memory
Motor processor
• Carries out actions
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Information Input and Output
• Input channels are the five
senses
- With some more important than
others
- Vision primarily
• Output channels are human
effectors
- E.g., limbs, fingers, head, vocal
system
Vision
Two stages in vision
• physical reception of stimulus
• processing and interpretation of stimulus
Visual Perception
• How we can see?
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The Eye - physical reception
• mechanism for receiving light and transforming it into
electrical energy
• light reflects from objects
• images are focused upside-down on retina
• retina contains rods for low light vision and cones for
colour vision
• ganglion cells (brain!) detect pattern and movement
Marr’s Theory of Vision
• Vision can be explained with a three-level model
Primary Sketch
2½D Sketch
3D Sketch
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Environment: Visible Light
Humans have receptors
for (a small part of) the
electromagnetic
spectrum
- Have receptors sensitive
to (fire when excited by)
energy 400-700nm
- Snakes “see” infrared,
some insects ultraviolet
- What would life be like if
humans could see other
parts of electromagnetic
spectrum???
Interpreting the signal
Size and depth
- visual angle indicates how much of
view object occupies
(relates to size and distance from eye)
- visual acuity is ability to perceive
detail (limited)
- familiar objects perceived as constant
size
(in spite of changes in visual angle when far away)
Interpreting the signal (cont)
• Brightness
- subjective reaction to levels of light
- measured by just noticeable difference
- visual acuity increases with luminance as does
flicker
• Colour
-
made up of hue, intensity, saturation
cones sensitive to colour wavelengths
blue acuity is lowest
8% males and 1% females colour blind
Proximity
Optical Illusions
the Ponzo illusion
the Mueller-Lyer illusion
Optical Illusions
Human Eye: Chromatic Aberration
• Normal:
Color Blindness
- trichromatic
• No red, green, blue: dichromatic
• The most prevalent causes are confusion
between red and green
• suffer from a deficiency in perceiving
blue/yellow differences
Mechanism
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Reading
• Several stages:
•
visual pattern perceived
decoded using internal representation of
language
•
interpreted using knowledge of syntax &
semantics
• Word shape is important to recognition
• Negative contrast improves reading from
computer screen
Word shapes
Proof-Reading Illusion
What if ….
• User visual attention is need for
another activity
- Driving & cell phone / gpa navigation….
• Were colour blind?
• Needed reading glasses?
• Had really poor eye sight that couldn’t
corrected by glasses?
• User was blind?
Hearing
• Provides information about environment:
distances, directions, objects etc.
• Humans can hear frequencies from 20Hz to
15kHz
• Physical apparatus:
•
outer ear
- protects inner and amplies sound
•
middle ear- transmits sound waves as
vibrations to inner ear
•
inner ear
- chemical transmitters are
released and cause impulses in auditory nerve.
What if….
• Users are in a noisy environment
 Phone call/ text message?
• User hearing is below average
• User is deaf
Touch
• Provides important feedback about environment.
• May be key sense for someone who is visually
impaired.
• Stimulus received via receptors in the skin:
• thermo receptors - heat and cold
• nociceptors - pain
• mechanoreceptors - pressure (some instant,
some continuous)
• Some areas more sensitive than others e.g.
fingers.
• Kinesthesis - awareness of body position
Touch devices
• Interesting research in the
areas of sound and touch
– This is what is being used
for the ‘teaching visually
impaired kids to sign their
name’ project
• The nintendo wiis
multimodal with haptics
too
• Touch phones are so
NOW!
Pre-training circle
Post training circle
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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 ~ 200ms
- auditory ~ 150 ms
- pain
~ 700ms
• Increasing reaction time decreases accuracy
in the unskilled operator but not in the skilled
operator.
Movement (cont)
• Fitts' Law describes the time taken to hit a screen
target:
Mt = a + b log2(D/S + 1)
where: a and b are empirically determined constants
Mt is movement time
D is Distance
S is Size of target
targets as large as possible
distances as small as possible
Model Human Processor - Original
Memory
There are three types of memory function.
What is Attention?
• Definition
Attention is the focusing of perception on a limited range of
stimuli, leading to heightened awareness
• Explanation
- Our senses are constantly bombarded with images, sounds,
smells, tastes and touch
- How to deal with all this information in such a way as to make
sense out of it
- Human tendency is to avoid getting overloaded with
information
- This is done by employing the selective process of attention
 Withdraw from some things in order to deal efficiently with others
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Models of Attention
• Divided attention
Available capacity
• Focused attention
senses
Short term store
Possible activities
Processing
Example 1 (Preece, P. 103)
Focused Attention vs. Divided Attention
• An attention may be
- Focused attention
 Attending one event at a time out of several competing
stimuli
Example
 When several students in a class asking to their teacher
simultaneously
- Divided attention
 Ability to attend to more than one things at a time
Example
 When watching a video music
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Voluntary Attention vs. Involuntary Attention
• A further properties of attention is
- Voluntary attention
 Making a conscious effort to change attention
Example
 While driving a car and you see a mass fighting themselves on
the road side
- Involuntary attention
 When the salient characteristics of the competing stimuli grab
the attention
Example
 While working with a computer and heard your favorite music
in the next room
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Attention and Automatic Action
• Frequent activities become automatic.
• Carried out without conscious attention.
• User does not make conscious decision.
Sensory Memory
• Information from the external world is initially
registered by the specific sensory stores
- Like input buffers holding a direct representation of sensory
information
• Only a small fraction of all information entering the
sensory store is attended for further processing
 Moving a finger in front of the eyes
 We cannot see the finger more than one place at once
 Firework display
• The information is lost by being written over by
successive information or through the process of decay
- Information remains in sensory memory very briefly, in the
order of 0.5 seconds
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Short-term memory (STM)
Scratch-pad for temporary recall
rapid access ~ 70ms
rapid decay ~ 200ms
limited capacity - 7± 2 chunks
The human ability to group information into related small sets
(chunks).
Short-term Memory
• Information from sensory store is attended to
and selected for further processing in the shortterm store
• It is also called working memory
• Information reaching the short-term memory
store is actively processed and may then be
transferred into the long-term memory store
Sensory memory
Iconic
Echoic
Haptic
Attended
Short-term memory
or
Working memory
Short Term Memory
• Example
35 x 6
Step 1: 30 x 6
Step 2: 5 x 6
Ans: step 1 + step 2
Short Term Memory
• Example
212348278493202 (difficult)
0121 414 2626 (easy)
HEC ATR ANU PTH ETR EET
(The Cat Ran Up The Tree)
Capacity of Short-term Memory
•
Capacity to hold information is limited in time
-
•
Information remains in short-term memory very briefly,
in the order of 200 ms
Capacity to hold information is limited in amount
-
There are two basic methods for measuring memory
capacity
1. Determining the length of a sequence which can be remembered
in order
2. Items to be freely recalled in any order (say, in memory game)
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Concept of 7 ± 2
• An observation by George Miller (1956)
- The magic number 7 ± 2
- The number is the one most often known to user interface
developers
- People can recall somewhere between 5 and 9 things at one
time
Examples
- Let’s see the following sequence of digits and try to write
down as much of the sequence as you can
 364207120948
 The average can easily recall between 5 to 9 digits
- Now try the following sequence. Did you recall that more
easily?
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 03742 58 2376
Generalization of the 7 ± 2 Rule
• We can remember 7 ± 2 chunks of information
- Chunking information can increase the short-term memory
capacity
• This is very much relevant in user interface design
Example
- Command line interface in Unix
 A command has a number of parameters of options, to be applied in
a particular order, and it is going to be applied to several files that
have long path names
 The user then has to hold the command name, its parameters and
the file path names in short-term memory while he types them in
 For the user, task may cause problems if the number of items or
chunks in the command is more than 7
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What some designers get up to…
•
•
•
•
•
Present only 7 options on a menu
Display only 7 icons on a tool bar
Have no more than 7 bullets in a list
Place only 7 items on a pull down menu
Place only 7 tabs on the top of a website
page
 But this is wrong? Why?
Long-term memory (LTM)
Repository for all our knowledge
slow access ~ 1/10 second
slow decay, if any
huge or unlimited capacity
Two types
episodic - serial memory of events
semantic - structured memory of facts,
concepts, skills
Long-term memory (cont.)
• Semantic memory structure provides access to
information
• Represents relationships between bits of information
• Supports inference
• Model: semantic network
•
inheritance - child nodes inherit properties of parent
nodes
•
relationships between bits of information explicit
•
supports inference through inheritance
Long-term Memory
• Information entering the long-term memory is assumed to be
permanent
• Processed information are stored as knowledge, which can be
retrieved any subsequent time
Sensory memory
Iconic
Echoic
Haptic
Attended
Short-term memory
Rehearsal
or
Long-term memory
Working memory
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Long Term Memory
• Example
- the dog
chewed the
food
- the cat stole
the food
- the dog chased
the cat
dog
chewed
chased
cat
food
stole
Long-term memory - semantic network
Utah School of Computing
Student Name Server
slide 56
LTM - Forgetting
decay
•
information is lost gradually but very slowly
• new information replaces old: retroactive
interference
• old may interfere with new: proactive inhibition
• so may not forget at all memory is selective ….
• … affected by emotion - can subconsciously
`choose' to forget
LTM - retrieval
•
recall
•
information reproduced from memory
can be assisted by categories
•
recognition
•
information gives knowledge that it has
been seen before
Norman’s Notion of Knowledge
Norman (1988) introduced the notions
• Knowledge in the world  Recognition
- Information stored in the world
- Less load on memory
• Knowledge in the head  Recall
- Information stored in the memory
- Too load on memory
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Thinking: reasoning and problem solving
Reasoning
Deductive: derive logically necessary conclusion from
given premises.
e.g. If it is Monday then he will not go to work
It is Monday
Therefore he will not go to work.
Logical conclusion not necessarily true:
e.g. If it is raining then the ground is dry
It is raining
Therefore the ground is dry
Inductive Reasoning
Inductive: generalize from cases seen to
cases unseen
e.g. all elephants we have seen have trunks
therefore all elephants have trunks.
Humans not good at using negative evidence
Modes
• Modes – the same action means some
different depending on the “mode”
- Many examples abound
• Modes are likely to be confusing
Modes
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Digital alarm clock: Time v Alarm
Car stereo: Treble-Bass, Lt-Rt, Fr-Back
Emacs
Various finite state machines
Automobile controls
Remote for TV-CD-VCR
Universal Usability
• Gender differences
- No clear patterns have emerged
 Games
 Tend to be aimed at young males
 Highest demographic of online players: older
women
 Productivity tools
 Largely male designers
 Poor UI choices (KILL a process)
Universal Usability (cont.)
• Users with disabilities
- Designers must plan early to accommodate
users with disabilities
- Early planning is more cost efficient than adding
on later
- Businesses must comply with the "Americans
With Disabilities" Act for some applications
- Temporary disabilities (glasses, loud
environments)
• Elderly Users
- Including the elderly is fairly ease, designers
should allow for variability within their
applications via settings for sound, color,
brightness, font sizes, etc.
Usability Topic: Color
Blindness
• About 8% of men have color blindness of
some type, and about 0.5% of women
- Varies along ethnicity
• Misnomer: most people see color difference
of some kind
- Color deficiency
- Monochromacy, very rare condition
• Genetic condition, alteration of the cones in
the eye
• Most commonly expressed in red/green
deficiency, often with specific shared
Designing for Color Blindness
• Avoid red-on-green at all costs!
• Consider using magenta instead of red
- Avoid using magenta with blue
• Use redundant coding of information
- Use color and shape/location
• Avoid thin lines / small symbols
- For color-coded text, use bold fonts
Universal Usability (cont.)
• Designing for/with children
- Broad term: toddlers to teenagers
- Younger children: evolving dexterity, level of
literacy, short attention span
- Parental control and safety vs desire of
challenge and learning
Universal Usability (cont.)
• Some practical user types
- The Beginner
 Just starting out, possibly not very technical
 Will need lots of hand-holding, at least to start
 Ever try teaching your grandmother AOL?
- The Casual User
 Uses the system infrequently
 Uses short-cuts, occasionally needs help
- The “Technically Challenged” User
 Doesn’t know, doesn’t want to know!
 Will need lots of hand-holding (i.e., help system)
Questions
• The human eye has a number of
limitations.� Give three examples
• There are three types of human
memory.� List them
• Describe what is thought to happen
when people �forget� things
Culture
Fall 2011
Culture
• Up is better than down
- Religion, Dante, …
• When we refer to ourselves
- We point to our noses?
- Our chests?
• Point with index finger or hand ?
Fall 2011
Cultural & International Diversity
• Characters, numerals, special
characters, diacriticals
• Left-to-right v (right-to-left or vertical
reading)
• Date and time formats
- International standards
• Numeric and currency formats
Fall 2011
Cultural & International Diversity
• Weights and measures
• Telephones and addresses
- Fixed v variable length
• Names and titles
- Mr., Ms., Mme, M., Dr.
• SSNs, national IDs,
• Capitalization and punctuation
Fall 2011
Universal Usability (cont.)
• Cultural and international diversity
- Characters, numerals, special characters, and diacriticals
- Left-to-right versus right-to-left versus vertical input and
reading
- Date and time formats
- Numeric and currency formats
- Weights and measures
- Telephone numbers and addresses
- Names and titles (Mr., Ms., Dr.)
- Social-security, national identification, and passport
numbers
- Capitalization and punctuation
- Sorting sequences
- Icons, buttons, colors
- Pluralization, grammar, spelling
Which universal, which culturally-specific?
• .
Mapping
• Relationship between controls and their movements and
the results in the world
• Why is this a poor mapping of vcr control buttons (rewind,
play, fast forward, fast rewind)?
Mapping
• Why is this a better mapping?
• The control buttons are mapped better onto the sequence of actions
of fast rewind, rewind, play and fast forward
Why are Interfaces Important?
• Sit-down-and-use computers and software
- Don't read the manuals
• Usability is critical to software sales:
- In magazine ratings
- "User friendly"
• HCI-trained people build better interfaces
- Programmers don't think like end-users
- Exposure to different kinds of interfaces, problems
- User model, not system model
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• Briefly describe the main features that are you feel will
support the user of this operating system.
Logical or ambiguous design?
• Where do you plug the
mouse?
• Where do you plug the
keyboard?
• top or bottom connector?
• Do the color coded icons
help?
From: www.baddesigns.com
How to design more logically
- A. provides direct adjacent
mapping between icon and
connector
- B. provides color coding to
associate the connectors with
the labels
From: www.baddesigns.com
Mapping
- Which controls go with which rings (burners)?
A
B
C
D
Why is this a better design?
Palm Desktop Calendar
Fall 2011
Palm Handheld Calendar
Fall 2011
Example
An elevator panel will require buttons
for four floors (parking, main floor,
second and third floor), door open,
door close, stop, and activate
emergency intercom. Propose a
design for these buttons. Draw them
in a single row
Examples of Bad Design … and Why
- Elevator controls and labels on the bottom row all look the
same, so it is easy to push a label by mistake instead of a
control button
- People do not make same mistake for the labels and buttons
on the top row. Why not?
From: www.baddesigns.com
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