More on Vision and
Audition Abilities
ITM 734 Fall 2006
Dr. Cindy Corritore
Vision
 Two step: physical reception and
processing/interpretation/perception
 physical reception



know that eye focuses and moves (saccade)
focus area is Fovea –
key aspects of visual reception are color, light,
and movement


central is color and bright light, high acuity
peripheral is less light and movement
 ability to detect motion is innate
Copyright 2006 Corritore
2 of 41
Perception (vision)
 organize and interpret sensory information
 active process
 Strongly influenced by past experience,
education, cultural values, role requirements.
 Occurs in context.
Copyright 2006 Corritore
3 of 41
Law of Prägnanz
‘Of several geometrically possible
organizations, that one will actually be
perceived is the one that possesses the best,
simplest and most stable shape’.
Copyright 2006 Corritore
4 of 41
Law of Simplicity
perceive the top figure,
not the bottom , more complex
one.
Copyright 2006 Corritore
5 of 41
Gestalt thought
 perception is more than just a mirror image of
the real world
 perceive groups of things, see well-organized
patterns
Copyright 2006 Corritore
6 of 41
Gestalt Laws of Perceptual
Organization
 proximity – group close things
 similarity – group like things
 closure – fill in missing elements (complete
incomplete things)
 continuity – tend to see trends rather than
discrete elements (see a line, not two parts)
 symmetry – tend to group items bounded by
symmetrical borders
 familiarity – tend to group items that are
familiar together
Copyright 2006 Corritore
7 of 41
law of similarity
orientation
lightness
shape
Copyright 2006 Corritore
8 of 41
Law of Familiarity
Copyright 2006 Corritore
9 of 41
Gestalt Laws of Grouping
 Good Continuation – objects arranged on a straight
line or curve tend to be seen as following the
smoothest path and the objects tend to be perceived
together (as a unit)
 Proximity – objects that are close tend to be
perceived together
 Common Fate – when objects move in same
direction, we tend to perceived them together
 these can interact (not either or)
Copyright 2006 Corritore
10 of 41
Grouping
We see two lines, ab and cd – but not ad
Which grouping law?
Good Continuation
Copyright 2006 Corritore
11 of 41
Grouping
see columns rather than rows.
Which grouping law?
Proximity
Copyright 2006 Corritore
12 of 41
Grouping
see two groups of things –
What grouping law is this?
Common Fate,
Proximity,
Good Continuation
Copyright 2006 Corritore
13 of 41
Gestalt principles
 open question – what happens when the laws
are in conflict (ie. more than one apply)?
 bottom line 

user seeking structure in data
perception is active
Copyright 2006 Corritore
14 of 41
Key things to know about color
All humans divide hue into eleven basic categories: black,
white, red, green, yellow, blue, orange, pink, gray, brown
and purple (culture-independent).
2. The meanings that people attach to color changes with
culture. But it also changes with context in the same
culture. I. E., blue can sometimes mean power and at
other times sadness.
3. When there are more than about 6 colors, ability to pick
out individual elements declines.
4. Color similarity is the best way to convey that two things
are the same type. Color differences are the best way to
convey that two thingsCopyright
are 2006
different
type.
Corritore
15 of 41
1.
Factors affecting color
discrimination
 Learned Color-Object Familiarity
 remember colors better when shown familiar objects (a red
apple, green leaf, etc.) or color is correct for object.
 Retinal location
 best when objects imaged in fovea - you are looking directly
at it - and falls as the image is seen further in the periphery.
 degrades first for red and green and then blue and yellow
before failing completely.
 only in large screens
 Brief presentation
 Short durations impairs discrimination of similar colors.
 effect is greater with reds and greens and smaller with blues
and yellows.
Copyright 2006 Corritore
16 of 41
Mismatch
 Stroop effect: name the colour:
RED
GREEN
BLUE
YELLOW
BROWN
PURPLE
 Color has not been shown empirically to be
superior
Copyright 2006 Corritore
17 of 41
Human Vision
 Contrast
 Contrast is important for visual displays,
particularly for older users.
 Negative contrast (dark characters, light
background) is generally easier to read.
 Visual attention may be drawn by flashing /
movement, brightness, difference in a group
 different colors require refocusing
 slow
 eye strain
Copyright 2006 Corritore
18 of 41
Design Implications
 color should be redundant cue – why?
 color blind
 can only really differentiate 7-9 colors
 color interpretation varies
 warm appear to move towards, cool away
 cultural interpretations
 red US/China
 which colors most sensitive to in foveal area
(best with color)?

red/yellow
 different colors require refocusing
Copyright 2006 Corritore
19 of 41
Design Implications
 visual resolution higher than monitors
 from 28”, letter height of .1-.2” recommended
 eye very sensitive to peripheral movement –
draws attention
 brightness perception is individual


PDA screen design?
increase brightness, increase perception of
flicker
 context (and expectations) allows us to
disambiguate interpretation
Copyright 2006 Corritore
20 of 41
Design Implications
 sans serif fonts
 grouping
 consistency
 simplicity
 clutter
 eye movement

top left to bottom right
Copyright 2006 Corritore
21 of 41
Design implications:
Competing Groupings
 Colour
dominates
shape
 Shape
dominates
texture
 Motion can
dominate all
other features
Copyright 2006 Corritore
22 of 41
Reading
 special case of vision
 recognize word shapes

implications?
 fixate (longer) and saccade (jerky move)
 go back and forth – more so with complex text
 greater contrast (dark letters, light background)
– brighter, but more flicker
 read off paper faster than monitors
Copyright 2006 Corritore
23 of 41
ecological displays
 use naturally occurring cues in display,
particularly for motion

these cues called optical invariants represent physical properties that don’t
change like light deflection
 relates to 3D space the most
Copyright 2006 Corritore
24 of 41
optical invariant 1:
compression & splay
 compression of texture of a surface
indicates distance

indicates altitude of viewing
 splay is angle between two lines from
front to back

receding - depth
invariant – changeless, constant
Copyright 2006 Corritore
25 of 41
optical invariant 2:
optical flow
 as we move, items flow past us
 how they move past tells us how fast we are
moving and our heading (direction)

expansion point - point from which all
streaming is occuring (ahead of us)


stationary - cue for heading
add depth cues - more accurate
 binocular vision, motion parallax, etc.
Copyright 2006 Corritore
26 of 41
optical invariant 3:
time-to-contact (tau)
 time we estimate until we reach an object

related to our perception of the size of objects
Copyright 2006 Corritore
27 of 41
optical invariant 4:
global optical flow
 flow as it depends on person’s velocity and
altitude

fly low, things move faster
 bias - we estimate speed by global flow


bus vs. motorcycle
high cockpit plane taxi speeds problem - too
fast as global cues different - appeared they
were going slow
Copyright 2006 Corritore
28 of 41
optical invariant 5:
edge rate
 no. edges that pass by visual field per unit
time
 use this to judge speed


related to global flow and/or texture
broken lines in highway vs. static wheat field
Copyright 2006 Corritore
29 of 41
3-D Displays
 represent item in reality or third dimension
uses depth as another quantity value
 we aren’t good at judging this
Copyright 2006 Corritore
30 of 41
Biases
 tend to lay out space in perpendicular grids
 preferences (North at top; view from window)
 based on experiential knowledge



landmarks (where grocery store used to be)
route knowledge (go 3 blks, turn right)
survey knowledge - higher level map created
over time, over broad area
Copyright 2006 Corritore
31 of 41
Object recognition
 People naturally ‘fill in’ with continuity where
none exists; this works better for gentle
curves than sharp ones.
 birthday card ….
Copyright 2006 Corritore
32 of 41
Object recognition
 Components




feature coding
feature integration
Accessing stored structural object descriptions
accessing semantic knowledge about object
 Size and shape constancy

see elephant as same size and shape no
matter the orientation or distance (inborn?)
Copyright 2006 Corritore
33 of 41
Face recognition
 Special case of object recognition



store info about the person/face that is more
accessible than name
name comes after general person info
recognize holistic (face) before specifics
(analysis byparts; job, name)
 Built-in predisposition
Copyright 2006 Corritore
34 of 41
Design Implications
 change heavy cognitive loads (interpreting
data/numbers, etc) into lighter perceptual
loads (perceptualization )

spreadsheet graphics good example
Copyright 2006 Corritore
35 of 41
Design Implications
strategies- make like normal communication
1. provide visual feedback on user actions and
system activities



where you are
hourglass when working
progress bars
Copyright 2006 Corritore
36 of 41
Design Implications
strategies- make like normal communication
2. dynamic visualization in real time



virtual reality stockmarket
algorithm activation for educational purposes
Ben Schneiderman: star fields for large
databases (houses, movies)
3. must map salient features in consistent way
Copyright 2006 Corritore
37 of 41
Design Implications
strategies- make like normal communication
3. 3-D rendering


Xerox Parc bookshelf for net browser
starfields: www.ivee.com/applications
 all capitalize on human ability to perceive
Copyright 2006 Corritore
38 of 41
Sound Output
 Research on sounds scattered
 good aspects
 different sensory channel so richer experience (better
memory)
 good when sound maps to real things or things that make
sense (alarm for bad items) - real sounds (have meaning)
 tried to use in lieu of visual animation (eg. algorithm
analysis)
 data sonification (explore data by listening to it); blind
 bad aspects
 too much noise - can’t differentiate sounds
 noisy environment
 acclimate/habituate to noises (car alarms)
Copyright 2006 Corritore
39 of 41
Speech Output
 Problematic
 strategies
 words/phrases stored
 phone co. : sounds artificial
 limited vocabulary
 phonemes (sounds) - about 40 in English
 build words
 difficult as requires natural language precepts
 problems
 may imply intelligence if can talk well
Copyright 2006 Corritore
40 of 41
Future Developments
 Earcons
 opportunistic, mobile communication
 http://www.hubbubme.com/
 multimedia - kind of a vast unknown
 multimodal  speech, vision, gesture
 haptic interface
 real world example
 movie clip
Copyright 2006 Corritore
41 of 41