Colin Wares Information Visualization

1
Colin Wares Information Visualization

• Kathryn Summers
• 2003

2
Semiotics and perception

• Symbols and their meanings
• Pictures
• Realism vs. convention
• Words
• Sensory vs. arbitrary
• Sensoryno need to learn, rapidly processed, not
  culture-specific
• Arbitraryhard to learn, easy to forget,
  culture-specific, can change quickly, but are
  formally powerful

3
Affordance theory

• Affordancesphysical properties of the
  environment that invite/support action and that
  are directly perceived (Gibson 1986)
• Gibson assumed that perception is action-driven,
  that we primarily perceive possibilities for
  action (legacy of evolution)
• Cognitive model of affordancesthe notion of
  learned (or socially constructed) affordances
  such as links or submit buttons

4
Opponent process color theory

• Luminance is based on input from all three cones
• Red-green is based on the difference between
  long- and middle-wavelength cones
• Yellow-blue is based on the difference between
  short wave-length cones and the sum of the other
  two

Long (red)
luminance
R-G
Medium (green)
Y-B
Short (blue)
5
Properties of color channels

• Luminance, or black-white channel, carries the
  most detail
• The R-G and Y-B channels only carry 1/3 as much
  detail
• Stereo perception, and perceived speed of motion,
  and even shape are based mostly on luminance
• We adapt to colored lightso that the neutral
  point for white shifts (for example, indoor
  light is yellow, but we still perceive white as
  white)

6
Color in interface design

• Some colors seem to be cross-cultural black,
  white, red, yellow, green, blue are the most
  standard brown, pink, purple, orange, and gray
  are the next most common
• Most people can reliably identify pure yellow
• There seem to be two pure greens, one at 514 nm
  and one at 525 nm (about 1/3 of people)
• Appearance of colors will change in context
• Use high-saturation colors to code small objects
• Use low-saturation colors for large areas

7
Perceptual processing

• Stage 1pre-attentive processing (20 of cortical
  neurons)
• Parallel processing (fast)
• Data-driven
• Color, motion, elements of form, contour,
  orientation, texture
• Short-term memory
• Stage 2
• Visual field segmented into regions and
  two-dimensional patterns

8
Stage 3 perceptual processing

• Sequential processing (slow)
• Action-oriented processing
• Semiotic processing
• Goal-driven
• Involves working and long-term memory

9
Spatial contrasts

• Spatial frequency
• Orientation
• Contrast
• Phase angle (lateral displacement of pattern)
• Area covered by the pattern

10
How do we process objects?

• Recognition vs. recall
• Recognition
• Image-based
• Structure-based

11
Image-based research

• Subjects shown 2560 pictures, one every 10
  seconds, for seven hours spread over four days
  (Standing et al. 1970)
• Could identify ones they saw from ones not seen
  with 90 accuracy
• Research shows that searching through an image
  store may be faster if images presented in a
  quick series displayed in the same spot than if
  particpant must scan through a matrix of
  thumbnails.

12
More image research

• Subjects shown images too briefly to identify,
  then a random pattern (to remove stimulus from
  iconic store) (Bar and Biederman 1998)
• Tests showed no recall of image
• 15 minutes later, recognition tested, and was
  higher than random
• Image primed the visual system
• Priming effect reduced if the image was rotated a
  few degrees.

13
Gestalt principles

• Proximity
• Good continuity
• Symmetry
• Similarity
• Common fate (objects that move together)
• Common region (Palmer 1992)
• Connectedness (connected by continuous contours)
  (Palmer and Rock, 1994)

14
Cognitive artifactsinformation visualization

• Much more complex information can be analyzed if
  its presented visually
• Memory aid
• A way to imagine transformations or additions
• Showing patterns
• Some representations seem natural they dont
  require training (such as a gray-scale coding of
  quantity)

15
Vision and data

• Visual objects cognitive group visual attributes
• Representing data values as visual features and
  grouping features into objects allows us to
  visually organize data and facilitate cognitive
  processing

16
The end

• Next weekmore about visual grouping,
  pre-attentive processing, motion, and patterns