Name that tune.
Song title? Performer(s)?
R.G. Bias | rbias@ischool.utexas.edu |
1
Sensation and Perception
Start of two weeks on
“The Knower”
1/24/10
R.G. Bias | rbias@ischool.utexas.edu |
2
Objectives
After this class you will be able to (it is my
hope!):
 Describe some eye and ear physiology
 Explain how the visual system works
(somewhat)
 Identify visual cues to depth
 Explain how perceptual and cognitive
psychology influence HCI designs
 Have an early appreciation for psychological
models
R.G. Bias | rbias@ischool.utexas.edu |
Designing Stuff
 In Week 1, I asked the question “What would a system
look like if we were designing it for dogs?”
– Wouldn’t be a lot of text.
– Wouldn’t require a lot of dexterity.
– Might code information in smells and tastes.
 But we’re designing systems for humans (usually!). So it
will behoove us to know something about how human
beings take in and process information.
 So, this is the first of four lectures on “The Knower.”
 Ultimately our goal will be to design information
systems to fit people instead of the other way around.
R.G. Bias | rbias@ischool.utexas.edu |
Human Information Processing
 How do human beings take in and process
information?
– Sensory psychology – how humans transform physical energy
(e.g., light and sound waves) into sensory signals to and in the
brain.
– Perceptual psychology – how humans interpret these sensory
signals as perceptions.
– Cognitive psychology – how humans think about these
perceptions, and previous experiences, and their own mental
creations, and . . .
– Psycholinguistics – The psychology of language -- what goes
on between the time I have a thought and you have the same (or
similar!) thought, whether I say it or write it.
R.G. Bias | rbias@ischool.utexas.edu |
Turning Energy into Sensations
 Vision
– The energy is light waves.
• Waves of different frequencies. Different frequencies get
perceived as different colors.
– The nerve cells are “rods” and “cones” in the retina in
the back of the eye.
 Audition
– The energy is sound waves.
• Waves of different frequencies. Different frequencies get
perceived as different pitches.
– The nerve cells are hair cells on the basilar
membrane
R.G. Bias | rbias@ischool.utexas.edu |
Ear Physiology
R.G. Bias | rbias@ischool.utexas.edu |
Basilar membrane
R.G. Bias | rbias@ischool.utexas.edu |
Eye Physiology
R.G. Bias | rbias@ischool.utexas.edu |
Eye Muscles
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Visual Field
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Retinal Physiology
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Distribution of Rods and Cones
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Visible Spectrum
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Visual Sensitivity
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Neural Pathways
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Theories of Pattern Recognition
 Template Matching Theory
– We compare a visual stimulus with a set of
templates, or specific patterns that we have
stored in memory.
 Feature Analysis Theory
– More flexible – a visual stimulus is composed
of a small number of characteristics or
“distinctive features.”
– E.g., an “A” has a diagonal line, another
diagonal line, a horizontal line . . .
R.G. Bias | rbias@ischool.utexas.edu |
Aftereffect
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Ambiguous Figure
R.G. Bias | rbias@ischool.utexas.edu |
Sensation/Perception
 POINT: Perceptions are made up of more than
just a collection of sensations!
 OTHER things influence our perceptions, e.g.,
–
–
–
–
–
Our experiences
Our biases
The context
Our current emotional state
Etc.
 So, what does that have to say about designing
human-computer interfaces???
R.G. Bias | rbias@ischool.utexas.edu |
Bottom-up vs. Top-down
Processing
 Bottom-up
– Emphasizes the stimulus, and the sensory receptors
 Top-down
– Any theory of recognition must include something
OTHER than the stimulus – the ambiguous figure
proves this
– Also, check this out – the word superiority effect: we
can identify a single letter more accurately and rapidly
in the context of a word than in isolation, or in a string
of unrelated letters
R.G. Bias | rbias@ischool.utexas.edu |
Perceptual Psy – Color Vision
 Color perception – 3 types of cones (RGB)
A
B
R.G. Bias | rbias@ischool.utexas.edu |
Perceptual Psy -- Depth
 Different visual cues to depth
– Oculomotor vs. Visual
• Oculomotor – Lens accommodation and
extraocular muscle convergence are “read” by the
brain
• Visual: Binocular vs. Monocular
– Binocular – Stereopsis (retinal disparity)
– Monocular (next screen)
» Static
» Motion parallax
R.G. Bias | rbias@ischool.utexas.edu |
More Depth Cues
 Monocular
– Static
• Interposition
• Size
• Perspective
–
–
–
–
Linear perspective
Texture gradient
Aerial perspective
Shading
– Motion parallax
R.G. Bias | rbias@ischool.utexas.edu |
Monocular Cues -- Interposition
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Monocular Cues -- Size
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Object Constancy
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R.G. Bias | rbias@ischool.utexas.edu |
Monocular Cues – Linear
Perspective
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Monocular Cues – Texture Gradient
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Sooooo . . .
The grass really
IS
greener on the other side of the fence!!!
R.G. Bias | rbias@ischool.utexas.edu |
Monocular Cues – Aerial
Perspective
R.G. Bias | rbias@ischool.utexas.edu |
Monocular Cues -- Shading
R.G. Bias | rbias@ischool.utexas.edu |
Monocular Cues – Motion Parallax
R.G. Bias | rbias@ischool.utexas.edu |
Resources
 www.britanica.com
 Matlin, M. W. (2009). Cognition. Hoboken, NJ: John
Wiley and Sons, Inc.
 Blake, R., & Sekuler, R. (1980). Perception. McGrawHill.
 A discussion of sensation vs. perception:
http://www.learninginfo.org/sensation-perception.htm
 Good size constancy demo:
http://psych.hanover.edu/KRANTZ/SizeConstancy/index.
html
 A decent, half-hour video:
http://video.google.com/videoplay?docid=8724039763795336038#
R.G. Bias | rbias@ischool.utexas.edu |
 Today’s song was “Soft Parade” by The
Doors.
 Why do you suppose we chose to play it
before THIS class?
– (It was from The Doors’ album “Perception.”)
R.G. Bias | rbias@ischool.utexas.edu | 36