1. Attention and Scene Perception8
Attention and Scene Perception

2. The Physiological Basis of Attention
Three ways responses of a cell could be changed by attention:
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3. The Physiological Basis of Attention
Attention could enhance neural activity
Attention to a specific part of the visual field causes neurons to code those locations to have increased activity
This increased activation has been detected using fMRI technology

4. Figure 8.15 Spotlights of attention in the human brain
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5. The Physiological Basis of Attention
Attention could enhance the processing of a specific type of stimulus
Fusiform face area: An area in the fusiform gyrus of human extrastriate cortex that responds preferentially to faces in fMRI studies
Parahippocampal place area: A region of cortex in the temporal lobe of humans that appears to respond strongly to images of places (as opposed to isolated objects)

6. fMRI reveals that different pieces of the cortex are activated by faces and by places
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7. What can go wrong: Disorders of Visual Attention
Neglect: inability to attend to or respond to stimuli in the contralesional visual field
Typically, neglect of the left visual field after damage to the right parietal lobe
Contralesional field: The visual field on the side opposite a brain lesion
For example, points to the left of fixation are contralesional to damage to the right hemisphere of the brain
Ipsilesional field: The visual field on the same side as a brain lesion

8. Figure 8.21 Five images through the brain of a neglect patient (viewed as though from above)
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9. Figure A neglect patient would produce this sort of result if asked to cross out all the lines on the page
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10. Figure 8.23 This is what can happen when a neglect patient tries to copy a drawing
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11. Disorders of Visual Attention
Attention can be object-based
Evidence from neglect patients indicates that they sometimes neglect one side of an object rather than one side of the visual field
Tipper and Behrmann’s (1996) experiment

12. Disorders of Visual Attention
Extinction: In visual attention, the inability to perceive a stimulus to one side of the point of fixation (e.g., to the right) in the presence of another stimulus, typically in a comparable position in the other visual field (e.g., on the left side)
Balint syndrome: Results from bilateral lesions of the parietal lobes
Spatial localization abilities are greatly reduced
Balint syndrome patients don’t move their eyes very much
Balint syndrome patients have simultagnosia: An inability to perceive more than one object at a time

13. Perceiving and Understanding Scenes
What does it mean to see more than one object?
How do we perceive entire visual scenes?

14. Figure 8.25 Spend a second or two looking at each of these pictures
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15. Perceiving and Understanding Scenes
Now look at this second version of the figure and see if you can tell what has changed...

16. Figure 8.26 Which of these pictures did you see in Figure 8.25?
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17. Figure 8. 26 Which of these pictures did you see in Figure 8. 25
Figure Which of these pictures did you see in Figure 8.25? (Answer key)
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18. Perceiving and Understanding Scenes
Change blindness: The failure to notice a change between two scenes
If the change does not alter the gist, or meaning, of the scene, quite large changes can pass unnoticed
Demonstrates that we don’t encode and remember as much of the world as we might think we do

19. Perceiving and Understanding Scenes
Local and global approaches to scene recognition
Local approach: Identify the individual objects in a scene and use the identities of the objects to determine what the scene is
Global approach: Identify the entire scene all at once, without identifying individual objects within it

20. Perceiving and Understanding Scenes
Local approach to scene recognition:
Scene recognition can happen very quickly
How might we quickly identify objects in a scene without having to look at each one?
Covert attentional shift: A shift of attention in the absence of corresponding movement of the eyes

21. Perceiving and Understanding Scenes
Global approach to scene recognition
Perhaps it is not necessary to recognize individual objects in order to recognize a scene
Spatial layout: The description of the structure of a scene without reference to the identity of specific objects in the scene
Open, enclosed, rough, smooth, natural, artificial, etc.

22. Figure 8.31 Spatial layout from global information
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