Selective Visual Attention: Feature Integration Theory

1
Selective Visual Attention Feature Integration
Theory

• PS2009/10 Lecture 9

2
Feature Integration Theory (FIT)

• Visual Search tasks
• Illusory Conjunctions
• Texture Discrimination

3
Visual Search Task

• Triesman and Gelade (1980)
• time to detect targets defined by a single
  feature is unaffected by the number of
  distracters
• time to detect targets defined by multiple
  features is affected by the number of distracters

4
Target defined by a single feature

• Time to detect Blue T unaffected by number of red
  S and T distracters

5
Target defined by multiple features

• Time to detect Blue T is effected by number of
  distracters - linear increase in search time.

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Visual Search Times

• Targets defined by a single feature (e.g. Blue)
• processing of features occurs in parallel (colour
  coded for all the items in the display
  independent of numbers.
• Targets defined by multiple features (e.g. Blue
  and T)
• serial search process

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Illusory Conjunctions

• Displayed for less than 200msec followed by a
  pattern mask
• Ss reported the digits and then details of the
  letters

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Illusory Conjunctions

• Ss good at reporting digits
• Ss made errors reporting letters and colours
• more of the errors were conjunction errors
• conjunction error - Ss says the saw a red letter
  T and a blue X

9
Texture Discrimination

• E.g. Beck (1966)
• Ss rate T as more similar to T
• Ss find it harder to discriminate the boundary
  between T and L

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Texture Discrimination

• T and T can be discriminated on the basis of a
  single feature - orientation
• T and L only distinguishable when the features
  are combined

11
Problems with FIT 1

• Verzi Egeth (1984)
• Ss showed evidence of illusory conjunctions
• report BIG but written in blue ink
• Colour Blue was not present

12
Problems with FIT 2

• Illusory conjunctions influenced by the meaning
  of words in the display
• illusory conjunctions are not just a perceptual
  phenomenon

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Problems with FIT 3

• Humphreys et al (1985)
• Time taken to detect target not influenced by the
  number of distracters.

14
Attentional Engagement Theory

• Similarity between targets and distracters
  increases search time.
• Similarity between distracters reduces search
  time.