1. Sensation and Perception
Chapter 6

2. Sensation

3. The Eye
Preview Question 5: How does the eye transform light energy into neural messages?

4. Photoreceptors
E.R. Lewis, Y.Y. Zeevi, F.S Werblin, 1969

5. Perception

6. Test your Blind Spot
Use your textbook. Close your left eye, and fixate your right eye on the black dot. Move the page towards your eye and away from your eye. At some point the car on the right will disappear due to a blind spot.

7. Bottom-up Processing
Analysis of the stimulus begins with the sense receptors and works up to the level of the brain and mind.
Letter “A” is really a black blotch broken down into features by the brain that we perceive as an “A.”

8. Feature Detection
Nerve cells in the visual cortex respond to specific features, such as edges, angles, and movement.
Ross Kinnaird/ Allsport/ Getty Images

9. Visual Information Processing
parallel processing The brain divides a visual scene into subdivisions such as color, depth, form, movement, etc.

10. THE CHT Top-Down Processing
Information processing guided by higher-level mental processes as we construct perceptions, drawing on our experience and expectations.
THE CHT

11. Thresholds
Absolute Threshold: Minimum stimulation needed to detect a particular stimulus 50% of the time.
Proportion of “Yes” Responses
Stimulus Intensity (lumens)
Preview Question 2: What is are the absolute and difference thresholds, and do stimuli below the absolute threshold have any influence?

12. Subconscious Sense and Perception
Subliminal Threshold:
Priming
Length of effects

13. Adaptation/Habituation
Stare at the image, don’t move your eyes around

15. Perceptual Organization
Preview Question 16: How did the Gestalt psychologists understand perceptual organization?

16. Flipped image

17. Figure/Ground Time Savings Suggestion, © 2003 Roger Sheperd.
Preview Question 17: How do figure-ground and grouping principles contribute to our perceptions?
Time Savings Suggestion, © 2003 Roger Sheperd.

18. Grouping

19. Depth Perception Visual Cliff
Preview Question 18: How do we see the world in three dimensions?
Innervisions
Visual Cliff

20. Binocular Cues
Retinal disparity: Images from the two eyes differ. 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. You will see a “finger sausage” as shown in the inset.

21. Monocular Cues
Relative Size: If two objects are similar in size, we perceive the one that casts a smaller retinal image to be farther away.

22. Monocular Cues
Interposition: Objects that occlude (block) other objects tend to be perceived as closer.
Rene Magritte, The Blank Signature, oil on canvas,
National Gallery of Art, Washington. Collection of
Mr. and Mrs. Paul Mellon. Photo by Richard Carafelli.

23. Monocular Cues Relative motion:
Preview Question 19: How do we perceive motion?

24. 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.
© The New Yorker Collection, 2002, Jack Ziegler
from cartoonbank.com. All rights reserved.

25. Monocular Cues
Light and Shadow: Nearby objects reflect more light into our eyes than more distant objects. Given two identical objects, the dimmer one appears to be farther away.
From “Perceiving Shape From Shading” by Vilayaur
S. Ramachandran. © 1988 by Scientific American, Inc.
All rights reserved.

26. Perceptual Constancy
Perceiving objects as unchanging even as illumination and retinal images change.
Preview Question 20: How do perceptual constancies help us to organize our sensations into meaningful perceptions?

27. Color Constancy
Color Constancy

28. The color and brightness of square A and B are the same.
Lightness Constancy
Courtesy Edward Adelson
The color and brightness of square A and B are the same.

29. Size-Distance Relationship
Alan Choisnet/ The Image Bank
From Shepard, 1990

30. Size-Distance Relationship
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.
Both photos from S. Schwartzenberg/ The Exploratorium

31. The Ames room is designed to demonstrate the size-distance illusion.

32. Perceptual Interpretation
How important is experience in shaping our
perceptual interpretation?

33. Facial Recognition
After blind adults regained sight, they were able to recognize distinct features, but were unable to recognize faces. Normal observers also show difficulty in facial recognition when the lower half of the pictures are changed.
Courtesy of Richard LeGrand

34. Sensory Deprivation
Kittens raised without exposure to horizontal lines later had difficulty perceiving horizontal bars.
Blakemore & Cooper (1970)

35. Top down emotional effects
Music
Fatigue
Carrying heavy versus light objects
Previous performance

36. Context instilled by culture also alters perception.
Cultural Context
Context instilled by culture also alters perception.
To an East African, the woman sitting is balancing a metal box on her head, while the family is sitting under a tree.

37. Taste Sweet Sour Salty Bitter Umami (Fresh Chicken)
Preview Question 14: How do we experience taste?
Sweet
Sour
Salty
Bitter
Umami
(Fresh
Chicken)

38. Gustation/Taste – a close-up view of the tongue

39. Why does some food taste “hot”?
Hot chili peppers are sensed by pain fibers in the tongue, which are activated by capsaicin
Was evolved in the peppers to prevent them from being eaten

40. Smell
Preview Question 15: How do we experience smell?

41. What is your favorite scent?

42. Smell and Memories