1. Chapter 7 - Visual Attention
Cognitive overview of the problem of attention

2. What is Attention?
“Everybody knows what attention is. It is taking possession by the mind, in clear and vivid form, of one out of what seem several simultaneously possible objects or trains of thought. Focalization, concentration of consciousness are of its essence. It implies withdrawal from some things in order to deal effectively with others , and is a condition which has a real opposite in the confused, dazed scatterbrain state … “
William James (1890)

3. What is Attention? ‘Taking possession of the mind’
Controlling the focus of attention; intentionality; “Please pay attention …”
‘one out of what seem several simultaneously possible objects’
Our apparent inability to attend to multiple things at once
‘It implies withdrawal from some things in order to deal effectively with others’
Attending has a cost
Attending is a limited capacity process
‘has a real opposite in the confused, dazed scatterbrain state’
Attending is the glue that keeps perception together

4. Attention: Selecting some stimuli over others for further processing
Why select? Why not process all visual input?
Limited processing capacity
Limited processing capacity of what?
Response systems: Two hands, one mouth, etc.
Input: One pair of foveas
Use of distributed representations: When more than one pattern is activated simultaneously, interference or cross-talk may occur.

5. Coping with the problem of interference and cross talk
Reducing the degree of distributedness at higher levels of visual representation
Evidence of sparse population codes (e.g., IT face representations)
Binding attributes via synchronized oscillations
Selective Attention: Focusing processing on a selected portion of the scene
Reduces information overload

6. Selective Attention
Selective attention: Limits the processing to one portion of the scene at a time.
Stimulus selection could be based on:
location in a (retinotopic map)
object representation

7. Spatial-based Selection
Posner’s Spatial Cuing Procedure.
- See fixation cross
- Brightness change
- Respond to target onset
Fastest response to a target that occurs on the cued side (valid) and slowest when target occurs on the non-cued side (invalid).

8. Object-based Selection
Task
Told what dimension(s) to report
Fixation point
See target (~79 ms)
Pattern mask
Report
Target: Two overlapping objects, each with 2 dimensions:
Box: Height; Gap
Line: Texture; Orientation
Equally accurate reporting one or two dimensions from the same object
More accurate reporting two dimensions from the same object than one dimension from each of two objects. (Vecera & Farah, 1994, E1: 86% > 80%)
After Duncan (1980)

9. Visual Attention: The Glue that Binds
We normally experience our complex environments as a coherent world of integrated objects.
Remember: Sensory information (i.e., shape, color, motion) arrives in parallel and is processed by different pathways in brain.
To create useful mental representations of objects, we collect their features, bind them into the correct temporal and spatial bundles, and interpret these bundles to specify their real world origins.
This process depends upon focused attention.
If focused attention fails, binding may fail and we perceive illusory conjunctions (i.e., upon seeing two cars (red Focus and black Echo, may falsely report a red Echo).

10. Feature Integration Theory: Treisman (1998)

11. Limited Visual Input
Although we seem to have a detailed, highly veridical and continuous mental representation of visual world about us, visual input is limited.
Visual acuity is good only for foveal focus.
Eyes movement from one fixation point to another while viewing a scene.
Saccades: 3-5 saccades/sec, 40 – 50 msec each.
Fixations: ~300 msec, during which we pick up visual information.

12. Eye Movements: Saccades and Fixations

13. Change Blindness
Failure to detect supraliminal changes in a visual scene. (i.e., editing discontinuities in movies).
Flicker technique: In your demonstration, changes involved: color, size, location, presence/absence of objects in scene.
Winter 2006 data (Psych 3450)
Accuracy Latency
Central Interest % sec
Marginal Interest % sec

14. Two Empirical Issues to be Addressed from the Neuroscience Perspective
How does attention affect visual information processing at different stages?
What neural systems control the allocation of attention?