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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

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On Being Human

ITEC 4130

Fall 2009

Understanding humans
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
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
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


  • 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
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
Depth and Size PerceptionIt 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 clues1
Depth and Size PerceptionIt 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 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 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)

Xxxxx graphical representation at the interface
XXXXXGraphical 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
Compensation & Illusions







Reading it s pretty complicated
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
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.


  • 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


  • 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”


  • 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
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
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

  • pain: 700ms (slow and distance related)

The box model of memory
The Box Model of Memory

Sensory memories











Sensory buffers



Driven by attention

Semantic: facts, meanings, skills, concepts, understandings…

Episodic: events, time, place, emotion…

Scratch-pad for temporary recall

* rapid access (70ms)

* rapid decay (200ms)

* limited capacity (7 ± 2)

Recency effect:

recall of recent items best

Evidence for several working memories

The box model of memory1
The Box Model of Memory





Semantic memory structure

-provides access to information

-represents relationships between information

-supports inference


-recall based on meaning

-gives rise to meaning-related confusions

-eye witness testimony…


  • Focused

  • Sustained

  • Divided

  • Selective

  • Alternating


  • How to focus attention at an interface?

    • Structure the information

    • Others…


  • Moving information from STM to LTM?

  • Need to provide:

    • Structure

    • Meaning

    • Become familiar (through rehearsal)


  • 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


  • 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
Knowledge representation

  • Declarative knowledge = knowing that

  • Semantic networks

  • Frames

  • Scripts

  • Procedural knowledge = knowing how

  • Scripts

  • Production rules

Frame based model of semantic memory
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)

Script based memory
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
Production rules

  • Representation of procedural knowledge

  • Condition/action rules

  • if condition is matched, rule fires

Slips and mistakes
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