Visual Selective Attention

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What is the space-based view?

The space based view is that visual attention is directed to and on the basis of regions of space in a visual scene. These consists of models such as:

  • The spotlight model of visual attention - Posner (1980)
  • Zoom-lens model - Eriksen and St James (1986)
  • Multiple spotlights - Awh and Pashler (2000)

The basic idea is the same for all types: Objects that fall under the 'beam' of attention are subject to further processing with priority.

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What is the object-based view?

The object-based view expresses the idea that attention selects from objects themselves, rather than potentially empty regions of space. Duncan (1984) adopts this view and states that objects/groups are parsed in accordance with Gestalt laws, and are then subject to further processing.

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What is overt and covert attention?

  • Overt - You look at what you are attending to.
  • Covert - Attention moves independently of eyes (a mental shift).
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What is Posner's (1980) cueing paradigm?

  • Participants responded to presence of target - added a cue (either valid/invalid), used to attract attention to the area of space.
  • Target performance faster at the cued location compared to when the target appeared in the invalid location.
  • 80% of trials were valid (to build up expectation). Remaining 20% would be invalid. Neutral trials were also included.
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How were time costs accounted for?

Time costs were accounted for by a three part process:

1) Disengaging attention.

2) Moving attention to the location.

3) Engaging attention at new location.

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What is Eriksen and St James' model? (1986)

Eriksen and co's model was the zoom-lens - we can increase/decrease the area of focal attention at will, just like a zoom lens.

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What did Laberge (1983) do/find?

Methods

  • Laberge reported findings supporting the zoom lens model.
  • In this study, five letter words were presented, and a probe requiring a rapid response was occasionally presented instead of the word. There were two conditions: 1) Focused - categorize the middle letter / 2) Unfocussed - categorize the whole word (leading them to adopt a broader attentional beam).

Results

  • Focused: Reactions fastest at central letter.
  • Unfocussed: Detecting the probe was equal for all locations.
  • This shows that the attentional spotlight/zoom lens can have a very narrow (letter task) or fairly broad (whole word) beam.
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What did Muller et al (2003) find?

  • This study also supports the zoom-lens claim.
  • 4 squares were presented in a semi-circle. 
  • Participants cued to focus attention on one specific square/two specific squares/all 4 squares.
  • Afterwards, 4 objects were presented and participants decided whether a target was among them.
  • When a target was present, it was always in one the cued squares. Used fMRI to assess brain function:
  • 1) Targets detected fastest at small attended region.
  • 2) Activation in early visual areas was most wide-spread when attended region was large and most limited when the attended region was small.
  • This supports the notion of the attentional beam being able to be made wide/narrow.
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What is the multiple spotlights view?

View created by Awh and Pashler (2000). 

  • It is a superior account of visual attention.
  • Attention is more flexible - can conserve resources by avoiding attending to irrelevant regions of space that fall between relevant areas.
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Zoom lens vs. multiple spotlights (A+P, 2000)

  • Study used a 5 x 5 grid containing 23 letters and 2 numbers. 
  • Asked to find 2 digits. 2 spatial cues presented before the display.
  • 80% predicting location of numbers / 20% invalid.
  • 1) Z-L prediction: Prediction covers both locations - easier to detect A than B
  • 2) M-S: Select cued location at the same time

Found:

  • No difference in detection speed of digits at A + B.
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What is Duncan's study of Object-Based Attention?

  • Stimuli: Showed participants a box and a line superimposed at the same location.
  • Box and line each had two properties: Box - Short/tall with gap on left/right. Line - Dotted/dashed and oriented to left/right.
  • Task: To report two object properties.
  • Found: Participants slower to report two properties that belonged to belonged to different objects, compared to two properties of the same object.
  • The two object cost is the idea that attention selects objects - if it selected space the two-objects would be selected (as they appear at the same location). 
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What did O'craven, Downing and Kanwisher study?

O'Craven, Downing and Kanwisher (1999) studied object-based selection. 

  • Stimuli: Two stimuli - a face and a house transparently overlapping at the same location, with one object moving slightly.
  • Task: Attend to the direction of motion of one of the objects, or to the position of the stationary target.

Predictions:

  • 1) If attention is location-based it should select both stimuli (both at the same location)
  • 2) If attention is object-based, one or the other image should be selected.

Found

  • Selective activations: When the face moved, it was slected resulting in activation of the FFA. When the house moved there was more activity in the parahippocampal place area - compelling evidence that attention can select multiple objects.
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What did Vecera and Farah (1992) claim?

  • Attention can operate in both ways.
  • Purely object based selection might arise when the task object requires object-centred representations of shape.
  • Attention is space-based when the task can be solved by detecting visual features in an array format by the visual cortex.
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What did Egly, Driver and Rafal (1994) do?

  • Tested both types of attention in one study, using an adaptation of the cueing paradigm.
  • Presented rectangles at either side of fixation. 
  • One end of a rectangle was cued (to draw attention).
  • Then a target appeared at one end of the rectangle. Task was to detect the target.
  • Conditions:
  • 1) Valid - cue indicated the location of the target.
  • 2) Invalid same object - the cue appeared in the same object as the target, but at a different end of it.
  • 3) Invalid different object - The cue appeared in a different object to the target.

Found:

  • Target detection faster on valid trials. Also faster in invalid same object trials compared to invalid different object trials.
  • Suggests that when cued to the wrong end of the object, the whole rectange was still selected (as predicted by object-based attention). 
  • Demonstrates both types selection in the same study.
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