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Find:. What does visual search teach us?. Cognitive processes! Speed & Accuracy Mechanisms Automatic or Attention Search strategy Parallel, Serial, random or… ?. Features. Find the odd item Discriminate by.. Color xxxx x xx Size x x xxxxx Orientation ------l--- Depth

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what does visual search teach us
What does visual search teach us?
  • Cognitive processes!
    • Speed & Accuracy
    • Mechanisms
      • Automatic or Attention
    • Search strategy
      • Parallel, Serial, random or…?
features
Features...
  • Find the odd item
  • Discriminate by..
    • Color xxxxxxx
    • Size xxxxxxx
    • Orientation ------l---
    • Depth
    • Movement xxxx-->

x

slide7

L

L

L

L

L

L

L

L

L

slide8

Feature search is easy!

  • Fast (300ms)
  • Parallel (0-10ms/item)
  • No attention needed

500

400

300

0 ms/item

5

10

15

# of items

conjunction search
Conjunction Search
  • Find...combination of features
    • 2 orientations (particular arrangement)
      • Find: L among Ts

T

T

L

T

T

slide10

T

T

T

T

T

T

T

T

T

L

T

T

T

slide12

T

T

T

T

L

T

T

T

T

T

T

T

T

slide13

Conjunction search is hard!

  • Slower
  • Sequential
  • Focused attention needed

Conjunction

40 ms/item

700

500

Feature

0 ms/item

300

5

10

15

# of items

slide14
Feature search is easy
    • Fast (300ms)
    • Parallel (<10ms/item)
    • Focused attention not needed (i.e.,Can use a distributed form of attention )
  • Conjunction search is difficult
    • Slow (>500ms)
    • Serial (>10ms/item)
    • Focused attention needed
what guides search
What guides search?
  • Environmental information.
what guides search1
What guides search?
  • Environmental information.
  • Internal cognitive process
    • Attention.
    • Memory?
    • Deterministic Process: Self-Organized Criticality (SOC)?
memory in visual search
Memory for locations in search (Kristjansso,2000)

Identity of objects accumulates over time (Treisman & Gelade, 1980)

Random repositioning of stimuli does not affect search RTs

(Horowitz & Wolfe, 1998)

Inattentional amnesia in search (Wolfe, 1999)

Memory in visual search?

We are able to keep track of where we look!Inhibition of return (Klein, 1982)

  • Failure to replicate inhibition of return(Wolfe & Pokorny, 1990)
slide22

Non-systematic eye-movements

Engle, 1977; Ellis & Stark, 1988;

Scinto & Pillalamarri, 1986;

Krendel & Wodinsky, 1960; Groner & Groner, 1982

visual search task
Visual Search Task

Find the upright

“T”

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

T

slide24

Map trajectory of eyes:

        • Duration & x,y coordinates for each fixation.----------------------------------------------------------
        • Differences between fixations
        • xn – xn+1 &yn – yn+1
        • Distance =(x2 + y2)1/2
        • Direction = Arctan (y/x).
slide25

Posner & Raichel, 1994). Images of mind. New York: Scientific American Series. W/ citation in Palmer, S. (1999). Vision Science: Photons to phenomenology. Boston: MIT.

slide26

Bluebird contributed by

www.Sierra foothill.org

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