On Being Human
ITEC 4130
Fall 2009
Understanding humans
Humans evolve much more slowly than
technology
There are limits to human capabilities
- knowing what they are helps us
understand what is going on
Three Views of Humans
How to model a human!
Humans are interpreters/predictors
- cog. psych. & AI
Humans are sensory processors
- sensory psych., EE & CS systems
Humans are actors in environment
-activity Th., ethnog., ecol. psych.
Humans as I/O machines
Senses
vision
hearing
touch
smell/taste
proprioception (positional feedback)
requires time to propogate back to
brain
kinesthesia (muscle memory)
instantaneous
golf swing or catching a ball
Vision
Two stages in vision
- physical reception of the stimulus
- processing and interpretation of stimulus
- red arrow green arrow problem
The physical apparatus: the eye
- mechanism for receiving light and
transforming it into electrical energy
More about the eye
The eye:
- the light it picks up is light that reflects
from objects
- images are focused upside-down on retina
- retina contains rods for low light vision
and cones for color vision
- ganglia distribution on the retina varies
by species (African plains vs tree dwellers)
Depth and Size Perception
It is a complex suite of clues
* visual angle indicates how much of field of
view object occupies
* Is your visual field circular?
* Test this using a marker on the board
* visual acuity is ability to perceive fine
detail
* predatory birds have very high visual acuity
* Eagles: 600,000 cones/sq mm
* Humans: 150,000 cones/ sq mm
Depth and Size Perception
It is a complex suite of clues
* familiar objects perceived as constant size
* law of size constancy
* as someone walks toward you you don’t think:
Man, that guy is getting taller by the second!
* Cues help perception of size and depth
* Accommodation (lens stretches)
* Occlusion
* Motion parallax
* Relative size (tied to size constancy)
* Aerial perspective (atmospheric)
Brightness
* Brightness is a subjective reaction to
levels of light
* Measured by just noticeable
difference
* Visual acuity increases with luminance
* Pinhole camera
* Reading is improved in bright light
Color Perception
* Color made up of hue, intensity,
saturation
* Cones sensitive to color wavelengths
* Blue acuity is lowest
* Green acuity is highest
* 8% males and 1% females color blind
(Red/Green confusion most freq)
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Graphical Representation at
the Interface
Graphical modeling and 3-D
Graphical coding
Graphical coding for quantitative data
Color coding
Color versus monochrome coding
Icons
Compensation & Illusions
http://blindspottest.com
http://en.wikipedia.org/wiki/Image:Gradient-optical-illusion.svg
http://en.wikipedia.org/wiki/Same_color_illusion
http://en.wikipedia.org/wiki/Grid_illusion
http://en.wikipedia.org/wiki/Ponzo_illusion
http://en.wikipedia.org/wiki/Image:Revolving_circles.svg
Reading… it’s pretty
complicated
“Stage” model of reading
(1) visual pattern perceived
(2) decoded using internal language
representation (pick out the words)
(3) interpreted using knowledge of
syntax, semantics, pragmatics
(what do these words mean?)
Perception in reading
* Reading involves saccades and fixations
* Saccades are rapid movements of the eye
* Without them, the retina would “saturate” and
you wouldn’t see anything
* Fixations are the stops in that movement
* Perception occurs only during fixations
* Otherwise the world would be blurred!
* AKA: saccade masking
* Word shape is important to recognition.
Hearing
Two stages in hearing
- physical reception of the stimulus
- processing and interpretation of
stimulus
-someone speaks to you
-you say “what?”
-but you figure out what they
said before they can answer
Hearing
* Provides information about environment:
* Distance
* Direction (but you can’t distinguish between directly in
front and directly behind you!)
* People can hear from 20Hz to 15kHz(I wish!)
* less accurate distinguishing between high
frequencies
* Auditory system filters sounds
* We can attend to sounds even in the presence of
background noise
* “cocktail party phenomenon”
Touch
* Receptors in the skin:
- thermoreceptors (heat and cold)
but you can’t distinguish which!
- nociceptors (pain)
- mechanoreceptors (pressure)
* Unevenly distributed across the body
* Some areas more sensitive than others
* fingers are more sensitive than your back
6th, 7th and 8th senses
Proprioception
internal awareness of your body position
(Through feedback)
Kinesthesis
awareness of body movement
(Through muscle memory)
Balance
vestibular organ of inner ear
visual cues as to orientation
awareness of body orientation
through proprioception
Movement & perception
Tight integration of
-perception & motor planning,
-movement execution
-feedback
proprioceptive, kinesthetic, vestibular and
visual
Response time = reaction time + movement time
-Movement time depends on age, fitness …
-Reaction time depends on modality
visual: 200ms
auditory: 150 ms
The Box Model of Memory
Sensory memories
vision
touch
auditory
Sensory
buffers
are
constantlyo
verwritten
Short-term/
working
memory
Long-term
Memory
Episodic
Semantic
Driven by
attention
Scratch-pad for temporary recall
* rapid access (70ms)
* rapid decay (200ms)
* limited capacity (7 ± 2)
Semantic: facts, meanings, skills,
concepts, understandings…
Episodic: events, time, place, emotion…
Recency effect:
recall of recent items best
Evidence for several working memories
The Box Model of Memory
Long-term
Memory
Episodic
Semantic
Semantic memory structure
-provides access to information
-represents relationships between information
-supports inference
-associative:
-recall based on meaning
-gives rise to meaning-related confusions
-eye witness testimony…
Attention
Focused
Sustained
Divided
Selective
Alternating
Attention
How to focus attention at an interface?
Structure the information
Others…
Consolidation
Moving information from STM to LTM?
Need to provide:
Structure
Meaning
Become familiar (through rehearsal)
Forgetting
Decay
Information lost gradually but slowly
Interference
New information replaces old (retroactive)
Old may interfere with new (proactive)
Inhibition
You can ‘choose’ to forget
Example:
Parking your car…
You intentionally forget all but the most
recent episode
Retrieval
Recall
* Information reproduced from memory
* Can be assisted by cues, (e.g. categories,
imagery, auditory input…)
Recognition
* Information gives knowledge that it has
been seen before
Knowledge representation
Declarative knowledge = knowing that
Semantic networks
Frames
Scripts
Procedural knowledge = knowing how
Scripts
Production rules
Semantic networks
Frame-based model of
semantic memory
Knowledge is organized in data structure
Slots in structure are instantiated with
particular values for a given instance
of data
...translation for CS people:
frames classes in the head;
slots  variables/methods in the head)
General knowledge as frames
Script-based memory
Scripts = using frames for stereotypical
processes (e.g. eating in a restaurant)
* used for interpreting situations
* generalize episodic-memory events
Production rules
Representation of procedural knowledge
Condition/action rules
if condition is matched, rule fires
Slips and Mistakes
Slips are errors in execution of correct
intention
Capture errors
Errors of attention
Mistakes are errors in selection of goal or
method for accomplishing it
Errors of knowledge