1. Unit 4: Perceptual Organization and Interpretation

2. Do-Now (In Journal) What is an illusion?
How can illusions influence and mislead our perception of a stimulus?
Provide an example of a perceptual illusion that you have experienced.

3. Perceptual Organization
What do you perceive when you observe this image?
Why do you think you perceive two facial images?

4. Perceptual Organization
Gestalt:
An organized whole
Tendency to integrate pieces of information into meaningful wholes

5. Form Perception Figure-ground:
The organization of the visual field into objects (the figures) that stand out from their surroundings (the ground)

6. Grouping
After distinguishing the figure from the ground, our perception needs to organize the figure into a meaningful form using grouping rules

7. Necker Cube Individual elements of this cube are 8 black circles, each
containing 3
converging white
lines. When we
view them together
we see a whole, a cube!

8. How do figure-ground & grouping principles contribute to our perceptions?
Our 1st perceptual task is to perceive any object (the figure) as distinct from its surroundings (the ground).

9. Grouping and Reality
Although grouping principles usually help us construct reality, they may occasionally lead us astray.

10. Depth Perception Depth Perception:
Ability to see objects in three dimensions although the images that strike the retina are two-dimensional
Allows us to perceive distance

11. Depth Perception Binocular Cues: Monocular Cues: Convergence
Retinal Disparity
Relative Height
Interposition
Light/Shadows
Texture/Detail
Motion Parallax
Linear Perspective
Relative Motion

12. Depth Perception: Binocular Cues
Depth perception enables us to judge distances. Gibson and Walk (1960) suggested that human infants (crawling age) have depth perception. Even newborn animals show depth perception.
Visual Cliff

13. Depth Perception: Binocular Cues:
Try looking at your two index fingers when pointing them towards each other half an inch apart and about 5 inches directly in front of your eyes. What do you see?

14. Monocular Cues
Interposition: if something is blocking our view, we perceive it as closer.
Relative Size: if we know that two objects are similar in size, the one that looks smaller is farther away.
Relative Clarity: we assume hazy objects are farther away.

15. More Monocular Cues
Texture Gradient: the coarser it looks the closer it is.
Relative Height: things higher in our field of vision, they look farther away
Relative Motion: things that are closer appear to move more quickly.
Liner Perspective: Parallel lines seem to converge with distance.
Light and Shadow: Dimmer objects appear farther away because they reflect less light.

16. Monocular Cues: depth cues, such as interposition and linear perspective, available to either eye alone.

17. Monocular Cues
Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the ones that are shaded on top are seen as “sticking out toward us”

18. We Depend on Monocular Clues
Light and Shadow: Nearby objects reflect more light to our eyes. If 2 objects identical in shape and size, the dimmer one appears further away. Also, our brain “assumes” that light comes from above.

19. We Depend on Monocular Clues
Relative height: We perceive object higher in our visual field as being further away.

20. Monocular Cues
Linear Perspective: Parallel lines, such as railroad tracks, appear to converge in the distance. The more the lines converge, the greater their perceived distance.

21. Perception of Movement
Apparent movement
Illusion that still objects are moving
Autokinetic illusion
Perceived motion of a single object due to eye movements on an ‘impoverished background’
Stroboscopic motion (Click here)
Created by a rapid series of still pictures
Phi phenomenon
Apparent motion created by lights flashing in sequence

22. Monocular Cues
Relative motion: Objects closer to a fixation point move faster and in opposing direction to those objects that are farther away from a fixation point, moving slower and in the same direction.

23. Perceptual Constancy Perceptual Constancy: Perceptual Set:
Perceiving objects as unchanging (having consistent shapes, size, lightness, and color) even as illumination and retinal images change
Perceptual Set:
A mental predisposition to perceive one thing and not another

24. Perceptual Constancy: Shape Constancy

25. Shape Constancy
But we can be fooled

26. Size Constancy

27. Size-Distance Relationship
The distant monster (below, left) and the top red bar (below, right) appear bigger because of distance cues.

28. Perceptual Constancy: Color Constancy

29. Perceptual Constancy: Light Constancy
The color and brightness of square A and B are the same.

30. Size-Distance Relationship: Ames Room
Both girls in the room are of similar height.
However, we perceive them to be of different heights as they stand in the two corners of the room.

31. Size-Distance Relationship: Ames Room
The Ames room is designed to
demonstrate the size-distance illusion.

32. 3-D Sidewalk Illusions

33. 3-D Sidewalk Illusions

34. 3-D Sidewalk Illusions

35. 3-D Sidewalk Illusions

36. 3-D Sidewalk Illusions

37. Perceptual Set
Emotions, expectation, and context ALL influence our perceptions

38. 36 73
373
2625
4099

39. Perceptual Set
A mental predisposition to perceive one thing and not another. What you see in the center picture is influenced by mixing both pictures.

40. Perceptual Set Other examples of perceptual set.
(a) Loch Ness monster or a tree trunk; (b) Flying saucers or clouds?

41. Influences of Perception

42. Even Culture Influences Context

43. Review How do gestalts influence our perception?
How do we use retinal disparity to understand depth?
What does perceptual set suggest about our abilities to perceive?
How do biological, psychological, and social-cultural influences affect our perception?