lecture 16 from a college level introduction to psychology course taught Fall 2011 by Brian J. Piper, Ph.D. (psy391@gmail.com) at Willamette University, includes anatomy of eye/brain, dorsal pathway, ventral pathway, figure/ground, many illusions, synesthesia

1. Sensation & Perception I: Vision
Brian J. Piper, Ph.D.

2. Goals
• Sensation
• Perception
• Myth: Perception = Sensation
• Reality: Perception ≠ Sensation

3. Terminology
• Sensation: the process by which sensory
receptors receives stimulus energy from our
environment
• Perception: the process of organizing &
interpreting sensory information

4. Psychophysics
• the study of the relationship between the
1795-1878
physical characteristics of stimuli & our
psychological experiences
• jnd: minimum difference a person can detect
between two stimuli
• Weber’s Law: 2 stimuli must differ by a
proportion (light: 8%, weight: 2%, tone: 0.3%)

5. Below jnd (Subliminal)
• A double-blind study had volunteers listen to
tapes for 4 weeks (memory or self-esteem).
• Self-reported memory and self-esteem was
measured before and after listening.
Label Reality
Memory Memory
Memory Self-esteem
Self-esteem Self-esteem
Self-esteem Memory
Greenwald et al. (1991). Psychological Science, 2, 119-122.

6. Predicted Results
• This study has four groups (Label/Material)
– Self-Esteem/Self-Esteem; Memory/Memory; Self-
Esteem/Memory; Memory/Self-Esteem
• What impact, if any, will the labels have?
• In terms of Memory, please rank them from
highest (best) to lowest.
• In terms of Self-Esteem, please rank them
from highest to lowest.
Greenwald et al. (1991). Psychological Science, 2, 119-122.

7. Interpretation
Self-esteem and memory post-test were
expressed as relative to pre-test.
What discussion section would you write?
Greenwald et al. (1991). Psychological Science, 2, 119-122.

8. Interpretation
Self-esteem and memory post-test were
expressed as relative to pre-test.
What discussion section would you write?
Greenwald et al. (1991). Psychological Science, 2, 119-122.

9. Interpretation
• People that want to improve, improve.
• No benefits of subliminal messages consistent
with their advertised intent.
Greenwald et al. (1991). Psychological Science, 2, 119-122.

10. Energy to Action Potentials
http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html

11. Wave Properties
• Amplitude: height, small = dull; large = bright
• Wavelength: distance from peak to peak,
determines color:
– blue < green < red

12. Wavelength
Violet Indigo Blue Green Yellow Orange Red
400 nm 700 nm
Short wavelengths Long wavelengths
Different wavelengths of light result
in different colors.

13. The Eye

14. Parts of the eye
1. Cornea: Transparent tissue where light enters
the eye.
2. Iris: Muscle that expands and contracts to
change the size of the opening (pupil) for light.
3. Lens: Focuses the light rays on the retina.
4. Retina: Contains sensory receptors that process
visual information and sends it to the brain.

15. Retina
Retina: The light-
sensitive inner
surface of the eye,
containing receptor
rods and cones in
addition to layers of
other neurons
(bipolar, ganglion
cells) that process
visual information.

16. Optic Nerve, Blind Spot & Fovea
Optic nerve: Carries neural impulses from the eye to the brain.
Blind Spot: Point where the optic nerve leaves the eye because
there are no receptor cells located there.
Fovea: Central point in the retina around which the eye’s cones
cluster.
http://www.bergen.org

17. 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.

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

19. Young-Helmholtz Trichromatic “Theory”
• Physician/Physicist Thomas Young
& Hermann von Helmholtz
predicted that the eye would
have three kinds of color
receptors. 1773-1829
1821-1894
“Whoever in the pursuit of science, seeks after immediate practical utility may rest assured that
he seeks in vain.”

20. Color Blindness
Genetic disorder in which people are blind to
green or red colors. This supports the
Trichromatic specialization of cones.
Ishihara Test

21. Visual Information Processing
Optic nerves connect to the thalamus in the
middle of the brain, and the thalamus connects to
the visual cortex.

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

23. Visual Information Processing
Processing of several aspects of the stimulus
simultaneously is called parallel processing. The
brain divides a visual scene into subdivisions such
as color, depth, form, movement, etc.

24. Dorsal & Ventral Streams

25. Figure/Ground
Edgar Rubin

28. Sandro Del-Prete: “Message d’Amour des
Dauphins” 1987

32. Grouping & Reality
Although grouping principles usually help us construct
reality, they may occasionally lead us astray.
Magazine. .© 1983 PCS Games Limited Partnership
Both photos by Walter Wick. Reprinted from GAMES

34. Which one is continuation?
Johann Christian Poggendorff

35. Parallel Lines?
Ewald Hering

36. Parallel Lines?
Johann Karl Friedrich Zöllner

37. Depth Perception
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.
Innervisions
Visual Cliff

38. 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

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

40. Which one is bigger?
Ponzo Illusion

41. Which one is bigger?
Ponzo Illusion

42. Which one is bigger?
http://www.youtube.com/watch?v=hdZHfzjJf-g Ponzo Illusion

43. Which one is bigger?
Hermann Ebbinghaus
1850-1909
Ebbinghaus Illusion

44. Volunteer?

45. Volunteer?
• Aoccdrnig to rscheearch at Cmabrigde Uinervtisy, it
deosn't mttaer in waht oredr the ltteers in a wrod
are, the olny iprmoatnt tihng is taht the frist and
lsat ltteer be at the rghit pclae. The rset can be a
toatl mses and you can sitll raed it wouthit a
porbelm. Tihs is bcuseae the huamn mnid deos not
raed ervey lteter by istlef, but the wrod as a wlohe.

46. Compare Darkness
Edward H. Adelson Checker Shadow Illusion

47. Compare Darkness
Edward H. Adelson Checker Shadow Illusion

48. Compare Darkness
Edward H. Adelson Checker Shadow Illusion

49. How many colors do you see?

50. Number-Color Synesthesia
V.S. Ramachandran
1951-

51. Number-Color Synesthesia

52. Static Image I: Akiyoshi Kitaoka

53. Static Image II: Akiyoshi Kitaoka

54. Mars Surface: Viking I-1976

55. Devil?

57. Not Politically Correct

59. Eye-tracking

60. “Fusiform Facial Area”

61. Prosopagnosia
• Inability to recognize faces
• Sensation without Perception Video
Worth -> Sensation & Perception

62. Selective Attention
• http://www.youtube.com/watch?v=vJG698U2Mv
o
• http://www.youtube.com/watch?v=Ahg6qcgoay4

63. Floating Cube
http://www.youtube.com/user/Rxe08?blend=8&ob=5

64. Street
Art
West Vancouver (15 sec):
http://www.youtube.com/watch?v=8r26AwT7PTM

65. Summary
• Perception > Sensation
• Retina -> Optic Nerve -> Thalamus -> Visual Cortex -> Beyond
• Illusions:
– Figure ground
– Faces
– “Motion”
– Impossible