1. Sensation & Perception
Exam 3: Review
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University) 1

2. Sensation & Perception
Ch. 7: Action
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
Ecological approach
Optic flow
The physiology of navigation
Skilled action
Linking sensory and motor functions

3. Perception reconsidered
J. J. Gibson’s ecological approach
All the studies we have seen so far are conducted in laboratory settings, in which stationary stimuli were given.
Perception is not a stationary experience.
Perception should be studied as it occurs in the natural environment.

4. Optic flow and a gradient of flow
A gradient of flow gives a strong cue for motion and depth perception

5. Demonstration:

6. The Physiology of Navigation
Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patterns

7. Neuron 1 in the monkey’s MST responds to an expanding stimulus but not a stimulus with circular movement. Neuron 2 responds to circular movement but not to expansion.

8. Physiological Links Between Sensory and Motor Functions
Optic ataxia
Patients suffering from this syndrome produce inaccurate reaching movements towards a target or object in space.

9. Experiment by Schindler et al.
Participants:2 groups
Patients with parietal lobe damage and normal control participants.
Participants performed two tasks
Bisection task - point to position between cylinders
Reaching task - reach between cylinders and touch a gray strip
Bisection task
In each trial, you saw two cylinders that were shifted different positions.
You had to point a place exactly midway between the cylinders.
The results of this study suggest that the damage to the dorsal stream keeps such patients from being able to avoid obstacles. However, further research is needed to provide more evidence that this is the case.

10. Experiment by Schindler et al.
Trial 1
Bisection task
In each trial, you saw two cylinders that were shifted different positions.
You had to point to a place exactly midway between the cylinders.
So, for each trial, you had to point different positions.
point
Trial 2
The results of this study suggest that the damage to the dorsal stream keeps such patients from being able to avoid obstacles. However, further research is needed to provide more evidence that this is the case.
point

11. Experiment by Schindler et al.
Trial 1
Reaching task
In each trial, you saw two cylinders that were shifted different positions.
You had to touch a gray strip that were 20 cm behind the cylinders.
So, for each trial, you had to extend your hand to different positions.
touch
Trial 2
The results of this study suggest that the damage to the dorsal stream keeps such patients from being able to avoid obstacles. However, further research is needed to provide more evidence that this is the case.
touch

12. Results Pointing task Reaching task Trial 1
The patients with parietal lobe damage and normal control were equally accurate
Reaching task
The patients kept reaching the same place even though cylinders were shifted in each trial.
touch
Trial 2
touch

13. Mirror neurons

14. Mirror neurons
Mirror neurons respond to a particular “kind” of action (e.g., grasping) AND observing someone doing the action.
The activity of a particular neuron in the premotor area of a monkey.

15. Video clip from NOVA (PBS)
15 min

16. Sensation & Perception
Ch. 8: Motion
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
The functions of motion perception
The direction of movement

18. 4 different ways to create the perception of movement
Real movement
The object is physically moving
Apparent movement
Displacement of objects
Induced movement
Movement aftereffect

19. Functions of Movement Perception
Survival in the environment
Predators use movement of prey as a primary means to location in hunting
Motion agnosia
Damage to the cortex resulting in inability to perceive movement
Extremely debilitating and dangerous for the patient
Instructor can use the case of the woman in the text as an example of motion agnosia.

20. Functions of Movement Perception - continued
Perceiving objects
Movement of objects or the observer’s movement through objects help perceive the 3D organization of stimuli
Kinetic depth effect - movement of an object’s 2-D shadow can change into perception of a 3-D object
This is an example of structure-from-motion
Perceptual organization

21. Figure 9.4 Setup similar to the one used by Wallach and O’Connell (1953) to demonstrate the kinetic depth effect.

22. Demonstration: structure-from-motion

23. Visual Pathway (MT)

25. The Physiology of Navigation
Optic flow neurons - neurons in the medial superior temporal area (MST) of monkeys respond to flow patterns

26. Neurons that are sensitive to a specific direction of motion.
Inhibitory connections

29. The intelligence of movement perception
Top-down processes
Certain stimuli (like the human body) have special meaning that affects perception

30. This slide can be used to talk about the experimental evidence for biological motion.
Figure 9.18 Frames from the stimuli used by Grossman and Blake (2001). (a) Sequence from the point-light walker stimulus. (b) Sequence from the scrambled point-light stimulus.

31. Biological Motion (Demonstration)

32. Depth and size
Monocular depth cues
Binocular depth cues

33. Monocular pictorial cues
Occlusion
Relative height
Relative size
Familiar size
Atmospheric perspective
Linear perspective

34. Leonardo da Vinci (1452-1519) Mona Lisa (1503)
There has never been an artist who was more fittingly, and without qualification, described as a genius. Like Shakespeare, Leonardo were from an insignificant background and rose to universal acclaim. Leonardo was the illegitimate son of a local lawyer in the small town of Vinci in the Tuscan region….
Mona Lisa (1503)

35. The Dreyfus Madonna: da Vinci 1469

36. The Santa Trinita Madonna: Cimabue (1260/80)

37. Linear perspective
Things get smaller when they are away.

38. Occlusion

39. Relative height

40. Relative size

41. Atmospheric perspective

45. Texture gradient

47. Two types of perspectives
Linear perspective
Atmospheric perspective

48. Belvedere: Escher

51. Binocular disparity
The binocular disparity arises when a given point in the external world does not project to the corresponding points on the left and right retinae
(Palmer, 1999, “Vision Science”)

53. Binocular disparity
Your two eyes are getting different images  disparity  double images
Corresponding points
Corresponding points
No disparity
disparity

54. Small disparity
Large disparity
No disparity

55. Horopter (Vieth-Muller circle)

56. small
distance
large
distance
Small disparity
large disparity

57. Sensation & Perception
Ch. 11: Sound, The Auditory System, and Pitch Perception
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
Sound stimuli, amplitude and frequency
Sound quality (timbre)
Ear (structure)
Place theory
Central auditory processing

58. Sound wave
Figure 1: Graphic representations of a sound wave. (A) Air at equilibrium, in the absence of a sound wave; (B) compressions and rarefactions that constitute a sound wave; (C) transverse representation of the wave, showing amplitude (A) and wavelength (taken from Britannica Online)

59. A sound wave is determined by two factors
Magnitude
Y axis
Frequency
X axis

60. Specifying a sound stimulus
Amplitude
Y axis
Decibel (dB)
Number of dB = 20 x log(P/P0)
(P: the sound pressure of the stimulus, P0: a standard pressure)
P0:=the pressure of a 1000Hz tone at threshold.
Frequency
X axis
Hertz (Hz)  one cycle per second

61. dB: Decibel dB? With p=200, p0(standard pressure level)=20
dB=20 x log (200/20)= 20 x log (10)
= 20 x 1= 20
with p = 2000
dB = 20 x log (2000/20)= 20 x log (100)
= 20x 2 = 40
With p = 20000
dB = 20 x log (20000/20)= 20 x log (1000)
= 20x 3 = 60

62. create a complex sound by combining simple sound waves
 Additive synthesis
reduce a complex sound wave into a collection of simple sound waves.
 Fourier analysis

63. A sound wave from clarinet.
Simple sound waves that make a sound of clarinet

64. Figure 11. 9 The frequency spectrum for the tone in Figure 11. 8d
Figure The frequency spectrum for the tone in Figure 11.8d. The heights of the lines indicate the amplitude of each of the frequencies that make up the tone.

65. Ear

66. Ear

68. Bekesy’s place theory

69. The wave reached the peak at a particular location.
A wave spreads.
The wave reached the peak at a particular location.
The height of the wave reaches the peak at P, and then gradually subsides.

70. Different locations of vibration peak are produced by different spatial frequencies.

71. Different frequencies of sound waves activate hair cells in different locations

72. A complex tone (440Hz, 880Hz, and 1320Hz)..
The auditory system basically carry out a “Fourier analysis”  treat a complex sound as a composite of simple waves.

73. Sensation & Perception
Ch. 12: Sound Localization
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
Auditory localization
Perceptual grouping
ch 12

74. Identifying the sound source in the horizontal coordinate
Interaural differences
Interaural time differences
Capture the difference in the time that a sound reaches the left and right ears
Interaural level differences
Capture the difference in the level of the sound intensity (sound pressure level) that a sound reaches the left and right ears
ch 12

75. ch 12

76. Sensation & Perception
Ch. 13: Speech Perception
© Takashi Yamauchi (Dept. of Psychology, Texas A&M University)
Main topics
Phoneme
Speech spectrogram
The segmentation and variability problems
Categorical perception
Multimodal speech perception, Top-down process
Speech perception and the brain

77. Some major problems in speech perception
The segmentation problem
How do we segment the individual words?
The variability problem
Variability from different speakers
Variability from a phoneme’s context
E.g., /d/ differs in “dig” “dug”

78. Stimuli Phonemes: The smallest unit of the sound system in a language
consonants and vowels
If you change a phoneme in a word, the meaning of the word is also changed. (e.g., hip  tip; cat  hat; dog  dig)
English has about 40 different phonemes
Every English word is produced by a combination of phonemes.
Different languages have different phonemes
E.g., Japanese does not distinguish r and l.
E.g., rice / lice; election / erection

80. Some major problems in speech perception
The segmentation problem
How do we segment the individual words?
The variability problem
Variability from different speakers
Variability from a phoneme’s context
E.g., /d/ differs in “dig” “dug”

81. Question:
How does the perceptual system handle these problems, and give us a coherent speech perception?

82. Using visual cues in speech perception
The McGurk effect (demonstration)
What am I saying? Play the clip several times, alternating between looking at the talking head while listening, and listening with your eyes shut. Most adults (98%) think they are hearing "DA" - a so called "fused respons" - where the "D" is a result of an audio-visual illusion. In reality you are hearing the sound "BA", while you are seing the lip movements "GA". The "McGurk effect" was first described by Harry McGurk and John MacDonald in "Hearing lips and seeing voices", Nature 264, (1976).

83. Using visual cues in speech perception
The McGurk effect (demonstration)
The "McGurk effect" was first described by Harry McGurk and John MacDonald in "Hearing lips and seeing voices", Nature 264, (1976).

84. Speech perception and the brain
Broca’s area
Wernicke’s area

85. Speech Perception and the Brain
Broca’s aphasia - individuals have damage in Broca’s area (in frontal lobe)
Labored and stilted speech and short sentences but they understand others
Wernicke’s aphasia - individuals have damage in Wernicke’s area (in temporal lobe)
Speak fluently but the content is disorganized and not meaningful
They also have difficulty understanding others