1. Features and Objects in Visual Processing

2. The Visual World is an Arrangement of Features
Color
Motion
Form
Depth
Orientation

3. Pre-attentive vs. Attentive Processing
Pre-attentive processing
Does the visual system register some basic features automatically (without attention)
if so, what features?
How would you know?

4. Pre-attentive vs. Attentive Processing
Indicators of Pre-attentive processing
1. processing precedes orienting - if you shift your attention to something or someplace because of some processing you did on the information there, you must have done that processing without attending

5. Pre-attentive vs. Attentive Processing
Indicators of Pre-attentive processing
2. processing done in parallel - if you can process features of several objects simultaneously, you must have done that processing without attention

6. Parts vs. Wholes
We see wholes, but the visual system initially sees parts (i.e. features) of objects

7. Parts vs. Wholes For example:
We see two rectangles, but the visual pathways initially detects small lines with some orientation

8. Parts vs. Wholes Simple features form boundaries
We see two rectangles, but the visual pathways initially detects small circles with some color

9. Parts vs. Wholes Conjunctions don’t form boundaries
We see only one rectangle (at least initially) because the boundaries of the inner one are made of conjunctions – these require attention to be perceived

10. “Early parsing of the visual field is mediated by separate properties, not by particular combinations of properties”

11. What does Treisman conclude from this observation?
“Analysis of properties and parts precedes their synthesis”
What is the “strong prediction” Treisman makes?

12. Illusory Conjunctions
“errors of synthesis”

13. Illusory Conjunctions
Identify the letter on the left of the screen and the digit on the right

14. Illusory ConjunctionsQ 4

15. Illusory Conjunctions
What colored shapes did you see?

16. Illusory Conjunctions
Illusory conjunction - when perceived combination of attributes was not present

17. Illusory Conjunctions
Illusory conjunction - when perceived combination of attributes was not present
Supports notion that primitive features are processed independently and then bound together to form objects
This is thought to require attention focused on the location of the object to be bound

18. Visual Search: finding a single item in a cluttered visual scene

19. Visual Search
Visual Search: finding a single item in a cluttered visual scene

20. Visual Search
Is there a green square?

21. Visual Search
Is there a green square?

22. Visual Search
Parallel search: like many independent spotlights

23. Visual Search
Serial search: each item is selected until target is found

24. Visual Search
Serial search: each item is selected until target is found

25. Visual Search
Serial search: each item is selected until target is found

26. Visual Search
Serial search: each item is selected until target is found

27. Visual Search
How could you test which kind of search was happening?

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

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

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

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

32. Visual Search
Search slope for color singletons is flat. What does this tell us about color and attention?

33. Visual Search
Search slope for shape singletons is flat. What does this tell us about shape and attention?

34. Visual Search
Conjunction search: NOT FLAT!

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

36. Visual Search Search Slopes can be flat for targets defined by:
color
orientation
curvature
motion
depth
What does this imply about these features ?
What does it tell us about conjunctions of features ?

37. Treisman’s 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
Focused attention is required to “bind” features together into objects