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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


Look for the red L

L

L

L

L

L


L

L

L

L

L

L

L

L

L


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


T

T

T

T

T

T

T

T

T

L

T

T

T


+


T

T

T

T

L

T

T

T

T

T

T

T

T


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


  • 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)


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


  • 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).


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


Bluebird contributed by Scientific American Series

www.Sierra foothill.org


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