1. Pre-attentive Visual Processing: What does Attention do? What don’t we need it for?

2. Parts vs. Wholes Simple features form boundaries

3. Parts vs. Wholes Simple features form boundaries

4. Illusory Conjunctions Q 4

5. Visual Search Search Slope: How long per item?

6. Visual Search Search Slope: How long per item?

7. Visual Search Serial Search - linear increase in search time with number of distractors

8. Visual Search Parallel search - search time is independent of distracter number

9. Visual Search Search Slopes can be flat for targets defined by: –color –orientation –curvature –motion –depth What does this imply about these features ?

10. Visual Search But there are some caveats: –What is a search asymmetry?

11. Search Asymmetry

13. But it’s the same discrimination…gaps vs. non-gaps !? What model does Treisman propose to explain search asymmetry along with other aspects of visual search?

14. Feature Integration Theory Early visual system parses scene into features represented in “feature maps” “Attention Spotlight” can be moved across an overlay of these feature maps to bind features together

15. Feature Integration Theory What term does Treisman use to describe the bundle of features at a specific location?

16. Feature Integration Theory Object Files are mental (neural?) representations of the features associated with an object –whenever an object is selected by attention its features are bound and an object file is opened –when the features of that object change, the object file is updated

17. Feature Integration Theory How did Treisman et al. test whether the visual system uses object files?

18. Feature Integration Theory Priming: observers are faster to respond to something they’ve just seen

19. Feature Integration Theory +

20. + G N

21. +

22. +

23. + G

24. What Letter?

25. Feature Integration Theory What was the result?

26. Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved

27. Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved Interpretation?

28. Feature Integration Theory What was the result? –Naming was faster if the prime occurred in the same box, even though the object had moved Interpretation? –visual system establishes object files (e.g. a box with a G in it) and updates them as the location and features of the object change

29. The Physiology of Attention

30. Physiology of Attention Neural systems involved in orienting Neural correlates of selection

31. Disorders of Orienting Lesions to parietal cortex can produce some strange behavioural consequences Parietal Lobe

32. Disorders of Orienting Lesions to parietal cortex can produce some strange behavioural consequences –patients fail to notice events on the contralesional side –Patients behave as if they are blind in the contralesional hemifield

33. Disorders of Orienting Lesions to parietal cortex can produce some strange behavioural consequences –patients fail to notice events on the contralesional side –Patients behave as if they are blind in the contralesional hemifield but they are not blind Called Hemispatial Neglect

34. Disorders of Orienting Patients will often “neglect” half of their visual field

35. Disorders of Orienting Hypothesis: Parietal cortex somehow involved in orienting attention into contralesional space