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CMPUT 301: Lecture 12
The Human
Lecturer: Martin Jagersand
Department of Computing Science
University of Alberta
Notes based on previous courses by
Ken Wong, Eleni Stroulia
Zach Dodds, Martin Jagersand
What Next?
• So far, mostly computer and program
developer’s perspective on design.
• For usable systems, we need to better
understand the human user.
• HCI:
– studying people, computer technology, and
ways these influence each other
– designing, implementing, and evaluating
interactive computing systems for human use
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Studying People
•
Humans are limited in their capacity:
1. Sensory properties limit what information can
be inputted. Seeing, hearing, touching
smelling etc.
2. Cognitive capacities limit what can be
perceived, processed and stored
•
This has important implications for
design.
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Cognitive Models
• Knowing how people think, learn, reason,
and communicate is critical to designing
systems to ease cognitive tasks.
• Cognitive models provide a method of
predicting user behavior and performance.
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Cognitive Model
• Model Human Processor:
– perceptual subsystem
– handle sensory stimulus
– “input”
– motor subsystem
– controls actions
– “output”
– cognitive subsystem
– does the processing to connect the above
– “compute”
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Cognitive Model
• MHP basics:
– interacting subsystems, each with processors
and memory
– sometimes serial, sometimes parallel
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Input-Output Channels
• Focus on:
–
–
–
–
vision (visual channel)
hearing (auditory channel)
touch (haptic channel)
movement
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Visual Processing elements and
Pathways
• Eye transforms light into
nerve impulses
• Optic chiasm splits left
and right visual fields
• LGN: Exact function
unknown. May have to
do with stereo.
• V1 (Striate cortex)
performs spatial filtering
/ coordinate transforms
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The Eye
The Biological Camera
• Lens, cornea and
fluids focus light.
• Six eye muscles
orient the eye
• Iris adjusts light
• Retina captures
images
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Retina
Converts light to nerve impulses
• Photoreceptor
converts light
• Other cell
layers perform
image
processing
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Photoreceptors
Rods and cones
Rods: Night vision, but no color.
125 million, none in fovea,
outnumber cones 20:1
Cones: Color sensitive, but poor light sensitivity
6.4 million, peak density in fovea
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Photopigment
Large molecule with two energy levels
• Cis retinal has
low energy
• Trans slightly
higher energy
• Incoming light
photon adds
energy =>
changes cis to
trans state.
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Interneurons and Ganglion
cells
Center-surround organization:
1. Light hyperpolarizes the rod and excites
the bipolar cell below it
2. But inhibitory connections through
horizontal cells suppress signals
3. Best response to localized “dot”
4. While stimulating surround only lowers
firing rate
• What is this???
Convolution!!! Im*[-1 2 –1]
-
+
-
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Disappearing figure?
• Focus steadily on first the left then the right
black dot
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Visual Perception
• Brightness:
– visual acuity increases with luminance
– perception of flicker also increases with
luminance
– issue:
– flickering bright, large monitors?
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Visual Perception
• Color:
– hue
– wavelength of light (470–640 nm)
– ~150 distinguishable
– lightness
– ~240 luminance levels
– saturation
– ~20 purity levels
– issue:
– how many colors?
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Visual Perception
• Color wheel:
– additive primaries
(light)
– subtractive primaries
(pigments, dyes)
– shade
(adding black)
– tint
(adding white)
– “relationships”
(harmonizing, contrasting, clashing)
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Visual Perception
• Perceiving color:
– photopigments of cones
– “red” (558 nm peak), 64%, actually yellow
– “green” (531 nm peak), 32%
– “blue” (420 nm peak), 4%
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Visual Perception
• Perceiving color:
– converted to opponent channels
– ratio of red to green
– ratio of blue to yellow
– ratio of black to white
– from red and green levels
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Visual Perception
• Color:
– acuity
– high to yellow, green, and orange
– low to deep blue
– issues:
– color blindness
(red/green deficiency most common)
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Visual Perception
• Color blindness test:
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Visual Perception
• Color blindness test:
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Visual Perception
• Focus:
– different hues focus at (physically) different
points (e.g., red versus blue)
– Attention focus
– can cause fatigue from refocusing
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Visual Perception
• Color guidelines:
– colors are effective maximally when they are
used minimally
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Visual Perception
• Color guidelines:
– use color consistently with user expectations
– stop
– go
– caution
– cold
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Visual Perception
• Color guidelines:
– use foreground and background colors that
contrast well
– e.g., highway signs
– color theory
– clashing colors
– opponent color channels
– red/green?
– blue/yellow
– black/white
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Visual Perception
• Color guidelines:
– avoid blue text, fine lines, small shapes
– lens absorbs blue
– saturated blue cannot be made to focus
– only 4% of cones are blue-sensitive
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Visual Perception
• Color guidelines:
– avoid saturated colors
– “angry fruit salad”, “circus”
– visual fatigue
– allow users to focus on their content
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Visual Perception
• Color guidelines:
– use color redundantly
– with brightness, shape, texture, etc.
– color blindness
– monochrome monitors
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Visual Processing
•
Processing:
•
•
•
–
–
Scan
Filter
Interpret
2D to 3D
fill in missing
information
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Dorsal and Ventral Pathways
Where/What or Action/Perception?
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Visual Processing
• Reading:
– saccades, fixations, regressions
– issues:
– type size
– line length
– leading
– word shape (varying or NON-VARYING)
– typeface (serif type, sans serif type)
– contrast (black on white or white on black)
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Hearing
• Sound:
– characteristics:
– pitch (20 Hz to ~20 kHz)
– loudness
– timbre
– processing:
– cocktail party effect
– issue:
– could be used more effectively in user interfaces
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Touch
• Sensory receptors:
– thermoreceptors
– heat and cold
– nociceptors
– intense pressure, heat, and pain
– mechanoreceptors
– pressure (force feedback)
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Touch
• Mechanoreceptors:
– rapidly adapting
– responds to immediate pressure, but stops
responding with continuous pressure
– slowly adapting
– responds to continuous pressure
– acuity:
– two-point threshold test
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Motor and Sensory areas
Central sulcus: Where sensory and motor
information (somehow) is unified.
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Short and long control loops
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Sensory-motor alignment
• Somatosensory and
primary motor areas
aligned across central
sulcus
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Pareital association
Integration of sensory information
• Exaple: Reaching to a visual goal
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Movement
• Reacting:
–
–
–
–
stimulus sensed
brain processes and produces response
brain signals appropriate muscles to move
time taken involves reaction and movement
time
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Movement
• Speed and accuracy:
– tradeoff?
– Fitt’s law
– time taken to hit a target (e.g., menu item) depends
on the size of the target and the distance to be
moved
– e.g., menus, pie menus, linear menus
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Human Memory
• Humans remember substance and meaning
over details.
• Humans tend to remember the unexpected
over the expected.
• Humans recognize patterns and form
associations.
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Human Memory
• Types of memory:
– sensory buffers
– short-term or working memory
– via attention (selective focus, interest)
– long-term memory
– via rehearsal
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Sensory Memory
• Sensory memory:
– iconic, echoic, and haptic memories
– constantly overwritten by incoming information
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Short-Term Memory
• Short-term memory:
– scratch pad for temporary recall of information
– rapid access (70 ms), but rapid decay
– limited capacity
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Short-Term Memory
• Memorize:
5358979323846
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Short-Term Memory
• Recall.
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Short-Term Memory
• Average performance:
7  2 digits in order
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Short-Term Memory
• Memorize:
780 492 5202
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Short-Term Memory
• Memorize:
HEC ATR ANU PTH ETR EET
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Short-Term Memory
• Exploit chunking and pattern abstraction.
• Recency effect (word recall):
– most recently presented words
versus words presented in the middle versus
words presented earlier
• Recency effect affects short-term memory.
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Short-Term Memory
• Characteristics:
– letters or words that rhyme are difficult to
distinguish
– rate of forgetting increases with task complexity and
amount of information
– even small amounts of information can be quickly
lost if there is distracting new information
– recall of names of items is usually better when
presented as pictures rather than words
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Long-Term Memory
• Long-term memory:
–
–
–
–
–
stores everything we “know”
huge capacity
relatively slow access (~100 ms)
slow decay
issue:
– do we really forget or
do we just find it harder to recall some things?
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Long-Term Memory
• Types of long-term memory:
– episodic memory
– events and experience represented in serial form
– semantic memory
– structured record of facts, skills, and concepts
(derived from episodic memories)
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Long-Term Memory
• Semantic memory model:
– semantic network:
– entities, relationships, attributes
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Long-Term Memory
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Long-Term Memory
• Long-term memory processes:
– storing information
– forgetting information
– retrieving information
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Long-Term Memory
• Storing information:
– total time hypothesis
– time spent learning is directly proportional to the
amount learnt
– distribution of practice effect
– learning time is most effective if distributed
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Long-Term Memory
• Memorize:
– list A
Faith Age Cold Tenet Quiet Logic Idea
– list B
Boat Tree Cat Child Rug Plate Church
– list C
Java Swing Class Object Interface Constructor
Method
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Long-Term Memory
• Memorize:
– list D:
The Midterm Exam Will Be on Oct 22
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Long-Term Memory
• Interesting and meaningful information is
easier to remember.
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Long-Term Memory
• Why do we forget?
– decay
– information held degrades over time until it is
forgotten
– interference
– new information causes old information to be lost
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Long-Term Memory
• Interference:
– retroactive
– new information replaces old
– e.g., new phone number
– proactive
– old memory interferes with new
– e.g., still thinking of the old phone number
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Long-Term Memory
• Retrieving information:
– recall
– information is reproduced from memory
– recognition
– information presented indicates that the information
has been seen before
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Long-Term Memory
• Memorize:
–
–
–
–
–
–
–
–
–
–
child
red
plane
dog
friend
blood
cold
bread
big
angry
• Peg list:
–
–
–
–
–
–
–
–
–
–
1 bun
2 shoe
3 tree
4 door
5 hive
6 sticks
7 heaven
8 skate
9 wine
10 hen
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Long-Term Memory
• Peg list:
–
–
–
–
–
–
–
–
–
–
• Recall vivid imagery.
1 bun
2 shoe
3 tree
4 door
5 hive
6 sticks
7 heaven
8 skate
9 wine
10 hen
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Long-Term Memory
• Visualize:
The engines roared above the noise of the crowd. Even in
the blistering heat people rose to their feet and waved their
hands in excitement. The flag fell and they were off.
Within seconds the car had pulled away from the pack and
was cornering round the bend at a desperate pace. Coming
down the straight the sun glinted on its shimmering paint.
The driver gripped the wheel with fierce concentration.
Sweat lay in fine drops on his brow.
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Long-Term Memory
• What color was the car?
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Thinking
• Two categories of thinking:
– reasoning
– process by which we use knowledge to infer
something new
– problem solving
– process of finding a solution to an unfamiliar task,
using knowledge we have
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Reasoning
• Deductive reasoning:
– deriving the logically valid necessary
conclusion from the given premises
– e.g.,
If it is raining, the ground is dry.
It is raining.
Therefore, the ground is dry.
– e.g.,
Some people are babies.
Some babies cry.
Some people cry?
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Reasoning
• Inductive reasoning:
– generalizing from cases we have seen to infer
information about cases we have not seen
– e.g.,
all elephants are gray?
– positive versus negative evidence
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Reasoning
• Exercise:
– each card has a number on one side and a letter on
the other (guaranteed)
– verify the statement …
– if a card has a vowel on one side, it has an even number
on the other
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Reasoning
• Abductive reasoning:
– reasoning from a fact to the action or state that
caused it
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Problem Solving
• Gestalt theory:
– beyond only reproducing known responses or
using trial and error
– involves insight and restructuring the problem
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Problem Solving
• Problem space theory:
– problem state space, with initial and goal states
– apply transition operators
– select operators using heuristics such as meansend analysis
– e.g., moving an office
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Problem Solving
• Analogy:
– mapping knowledge relating to a similar known
domain to the new problem
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Problem Solving
• Story:
A doctor is treating a malignant tumor. To destroy it, he
needs to blast it with high-intensity rays. However, these
will also destroy the healthy tissue surrounding the tumor.
If he lessens the intensity of the rays, the tumor will
remain.
How does he destroy the tumor?
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Problem Solving
• Analogous story:
A general is attacking a fortress. He can’t send all his men
in together as the roads are mined to explode if large
numbers of men cross them. He therefore splits his men
into small groups and sends them in along separate roads.
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End
• What did I learn today?
• What questions do I still have?
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