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1. We behave effectively with respect to the world. What makes that possible?

5. 1 2 3 4

14. Problem : the world is at some remove. How do we achieve action at a distance ? We behave effectively with respect to the world. What makes that possible? What are the mechanisms that allow perceptual agents to achieve action at a distance?

15. Phenomena What kinds of properties of the world are perceived? Philosophy What kinds of properties and theoretical assumptions should anchor our theory of perception? Physics What kinds of properties are present or “recorded” in the energy media of the world? Physiology What kinds of properties can sense organs and nerve cells “record” and how doe these sense organs influence the perception? What do we have to understand to understand the mechanisms of perception?

16. Phenomena What kinds of properties are perceived? Problem : the world is at some remove. How do we achieve action at a distance ? Themes from the Overview We behave effectively with respect to the world. What makes that possible? Philosophy What kinds of properties/assumptions should anchor our theory? Physics What kinds of properties are present or “recorded” in the energy media? Physiology What kinds of properties can sense organs and nerve cells “record”?

18. The image is ambiguous, impoverished. (1) It doesn’t match the world. (2) It doesn’t match our experience. E nvironment  O rganism link is bad therefore… Perception requires processes to elaborate input, constructing a series of representations of the world that increasingly come to resemble it. Examine the E  O link How good are the images? Molyneux’s Premise (1692): distance is not perceivable by eye A B C D A B C D

19. What gets linked? What do you need to fix the bad link? Experience  Knowledge: Empiricism 3 Old Guys who set the conceptual agenda An object in the world at some distance from me that goads me or stimulates me to act: distal stimulus or S D The pattern at a sense organ caused by an energy pattern in the world: proximal stimulus or S P

22. Müller’s Theory of Specific Nerve Energies  impose their own characteristics— “specific nerve energies”—on the mind.  This, not the physical properties themselves, is why the qualities for the different senses are different. ELECTRIC PULSE PRESSURE CHEMICALS Visual sensation OPTIC NERVE LIGHT Eye designed to capture light SOUND AUDITORY NERVES Auditory sensation Ear designed to capture sound

24. Normalcy is embodied in internal algorithms or rules. cues + rules = Unconscious Inference The input is a disjointed, inadequate copy of the world. Perception works by improving the copy via rules. Perception of the world is indirect .

25. The Perceptual Process: Attended Stimulus Environmental Stimulus Action Stimulus on the receptors Transduction Processing Perception Recognition Stimulus Perception Stimulus Energy Sensation Physiological sensation Perception Three key relationships Knowledge cues & rules Unconscious Inference

26. Berkeley: coupling of percepts uses meaningfulness of one to explain another Müller: the sensory apparatus itself contributes its character to the input Helmholtz: mental computations reflect internalized knowledge of the world and how it affects us. The nature of E  S influences the nature of S  P All share the theory of inadequate input  currency is converted into  currency: How does physical energy map onto psychological experience? Measurement is the key to making perceptual psychology a science World Energy Sensations Perception ignored link historically important links

27. The nature of E  S influences the nature of S  P  currency is converted into  currency: How does physical energy map onto psychological experience? Measurement is the key to making perceptual psychology a science World Energy Sensations Perception ignored link historically important links

28. Energy  Sensation  Experience Energy  Sensation E  S Physical  Psychological    Perceive event (  cat rubbing leg ) Event in world Pressure (  energy ) Sense properties of pressure (  ) e.g. amount, location. Pressure sensitive nerves Energy  Sensation Psychophysics

29. Anticipated by Weber (mid-late 1800s) If the amount of energy is too small, it’s not noticeable. Psychophysics looks at the E  S link minimum energy that can just be detected Say “now” when you see the gray square. Absolute threshold

30. Trial 1 Trial 2 No No No No No No Yes Yes Yes Yes Yes Yes Yes Yes Yes No Intensity (I) Determining the Absolute threshold: Method of Limits Trial 5 No No No No Yes Trial 3 No No No No No Yes Trial 4 No Yes Yes Yes Trial 6 Yes Yes Yes Yes Yes Yes No 3 4 5 6 7 8 9 10 2 1 11 12 0 6 5 4 1 3 2 Trial Smallest Intensity Detected 6 5 7 6 7 5 Absolute threshold Mean 6 6

31. Anticipated by Weber (mid-late 1800s) If change in amount of energy is too small, it’s not noticeable. Psychophysics looks at the E  S link Weber’s focus was on discriminating two detectable stimuli: How similar could they be and still be sensed as different? Not absolute change but relative change J ust N oticeable D ifference  I / I = K A change in intensity relative to the initial intensity equals a constant. – =

32. J ust N oticeable D ifference (JND)  I sensed is not absolute!! Rather, the JND is a constant threshold. Difference Thresholds: How similar can objects be and still be sensed as different? I2 I1 102 g 100 g I2 - I1 =  I I : physical intensity I2 I1 101 g 100 g Same

33. Consider what happens when we use different values of intensity (I) 100 + 2 = 102 2/100 = 1/50 (.02) 200 + 4 = 204 4/200 = 1/50 (.02) 400 + 8 = 408 8/400 = 1/50 (.02) The greater the value of I the greater must be the value of  I for a difference to be sensed. JND’s for all senses: - Vision (e.g. change in brightness) - Hearing (e.g. change in loudness) WEBER’S LAW: = K (a constant)  I I Intensity I JND I +  I  I I Change in I  I K

34.  I = 20 The correspondence between a physical stimulus and our perception of it is systematic but it is not always 1:1. I = 500  I = 500 smaller K  more sensitive lower threshold K = 1 I = 20 I = 1000  I = 500 K = .5 I = 20  I = 10  I / I = K 1st truly quantitative law of psychology Fechner (mid-late 1800s)  I I  I I .2 .5 1 Slope

35. Weber’s goal was to study jnd s ; Fechner’s insight was that such a quantification allows you to probe mental states . Fechner (mid-late 1800s) Demonstrated how mental activity could be measured quantitatively!! … also started to examine whether we can assume a  equivalence of changes in intensity of stimulation? Steven’s attempted to understand the relationships between  and intensity in his examination of Magnitude estimation.

36. 0 1000 2000 3000 Stimulus Intensity 300 200 100 10 Standard = 100 Response = 160 Response = 130 Response = 200 Response = 25 Response = 50 T1 T2 T3 T4 T5 Response = 150 Response = 225 Response = 350 Response = 90 Response = 95 300 200 100 10 0 1000 2000 3000 Stimulus Intensity T1 T2 T3 T4 T5 Standard = 100

37. Subjective intensity of magnitide (  ) is some constant multiplied by the intensity (I) to some power (n). Stimulus Intensity Magnitude Estimate n = the slope of the line in the log-log plot Perceptual Sense reflects Power Law Functions Log Stimulus Intensity Log Magnitude Estimate  = kI n

38. Implicit Metatheory: To say there is a absolute or noticeable threshold is to say that there are un-noticeable things. To say there is a just noticeable difference is to say that there are also un-noticeable differences. To say the perception is power law like is to say that the… Connection between mind & body is in the quantitative relation between mental sensation & material stimulus  I/I = k and  = kI n highlight slippage between  &  (not 1:1). How do you measure the change in stimulation? You need methods… … that yield quantities that can be put into law form Fechner formally developed Psychophysics as the methodology, a methodology that endorses a metatheory

41. Light: The stimulus for vision Electromagnetic radiation structured in waves * over space distance energy amplitude = Intensity Wavelength same amplitude different wavelengths multiple wavelengths (vs. pure) same wavelength different amplitude

42. Wavelength: most relevant for color vision… Complexity or Purity Different wavelengths hue multiple of wavelength saturation brightness Different intensities Amplitude ≈ Intensity Wavelength

44. Camera Obscura (Alhazen) Limitation : Doesn’t let in much light—blurry image Problem : Spatial ordering of rays reflected from the object have to be recovered from the divergent light. box with a pinhole as the eye Solution #1 : Allow one ray from each part of the object into the eye.

45. Limitation : Clear focus depends on the power of the lens and angle of divergence of light rays. Problem : Spatial ordering of rays reflected from the object have to be recovered from the divergent light. … while letting in enough light for a clear image. Allows larger hole  more light  sharper image Solution #2 : Use a lens that refracts light so that rays from the same point on the object converge .

46. Limitation : Clear focus depends on the power of the lens and angle of divergence of light rays. Problem : Spatial ordering of rays reflected from the object have to be recovered from the divergent light … while letting in enough light for a clear image. Different distance of object from eye  changes angle of light rays  Out of focus for that lens. Solution #2 : Use a lens that refracts light so that rays from the same point on the object converge .

47. … of objects at varying distances. Problem : Spatial ordering of rays reflected from the object have to be recovered from the divergent light …while letting in enough light for a clear image Solution #3 : Lens with variable optical power changes shape to accom- modate the distance of the object to the size of the eye.

49. Retinal Image is Starting Point for Vision … and we have two Visual Fields defined relative to fixation x : L VF projects to right side of each eye and on to the Right Hemisphere LVF RVF Right Visual Cortex

50. Retinal Image is Starting Point for Vision … and we have two Visual Fields defined relative to fixation x : R VF projects to left side of each eye and on to the Left Hemisphere Right Visual Cortex Regions of left eye correspond to regions of right eye At some point we have to (re)connect visual fields. L VF projects to right side of each eye and on to the Right Hemisphere LVF RVF Left Visual Cortex

55. How a pattern is experienced depends on where it projects on the retina Is there a cost to pooling signals? Is there a benefit to keeping signals separate? detail is missed: less acuity detail is noticed: greater acuity

59. Without stimulus there is a base level of spontaneous activity . Task: Find the region on the retina whose stimulation will change the resting level (higher or lower) of Ganglion “A”. How: Scan retina with stimulus to see where ganglion’s activity is affected ( where matters ) Homogeneous gray  spontaneous activity. Spot of light  greater than spontaneous activity Dark spot in area  less than spontaneous activity Within area  greater than spontaneous activity Outside area  less than spontaneous activity

60. Spontaneous firing rate is affected up or down concentric ON/OFF regions Ganglion cell’s receptive field (a collection of retinal cells) What happens with light outside the ON/OFF region? What is experienced depends on where it hits retina Assessing various ganglia yields a receptive field map  overlap, producing a mosaic covering the whole retina (also OFF center/ON surround cells) “ ON” response “ OFF” response Distribution of concentric ON/OFF regions arises from connections among preganglion collectors spontaneous rate excited rate inhibited rate spontaneous rate

62. Dark edges over OFF surround with light on ON center  vigorous response: whole receptive field is getting its preferred stimulus  detects and accents light/dark boundary Edges are preferred by this kind of cell. illuminate only the center dark bar on the surround What pattern on the retina would be preferred by a Center/Surround cell?

63. Consequences of antagonistic relationship between center and surround same  response to dif.  intensities dif.  responses to the same  intensity Constancy Illusions Good mapping in a limited range? Intensity of Center Response Intensity of Center Response Intensity of Center Response   

64. From what we know about acuity, how should size vary in different areas of the retina?  large in periphery; small near fovea Many:1 vs. 1:1—Receptive fields vary in size Physiological mechanisms are recovering edge and size information  building blocks of meaning. Small receptive fields respond best to small objects; large to large  beginning of object size extraction . From what we know about preferences of receptive fields, how should they respond to objects of different sizes?

65. Acuity : smallest high contrast detail perceived at a given distance Receptive fields have consequences for the kinds of patterns that go into Unconscious Inferences. What letter is this? F E A H O D P R Identification Acuity Can you see this? Detection Acuity 1 or 2? Pattern or gray? Resolution Acuity K

66. Note disparities between  and  made possible by lateral inhibition — mechanism that highlights edges through sideways connections among cells. Illusory consequences illustrate how it works.  dependence on “irrelevant” conditions (e.g., distance) The “private line” from foveal cones to the brain provides fine detail… … but it’s neurologically expensive  receptive field organization is important

69. Mach bands —regions of heightened and reduced brightnesses.

70. Intensity changes in stepwise fashion activity w/NO neighbor: 40 40 40 40 100 100 100 100 Inhibition from Left: -2 -4 -4 -4 -4 -10 -10 -10 Inhibition from Right: -4 -4 -4 -10 -10 -10 -10 -18 Total Output: 34 32 32 26 86 80 80 72 Perceived Lightness lightness does not. Receptors (activity - inhibition) Light Intensity 1 2 3 4 5 6 Position high low Light Intensity 100 40 a b c d e f g h

75. Receptive fields care about size & shape… … but not orientation. Orientation influences what objects mean  Pool some more. To overcome mosaic, connect receptive fields. ” reduced rate: stimulus hits both excitatory and inhibitory cells

76. Receptive fields overlap Across a collection of receptive fields, orientation matters Collection reports to cells in the cortex . They have receptive fields too Record from 3 cortical cells Cortical cells do edge detection but more cleverly Cortical receptive field shapes are not uniform Hubel & Wiesel (1959, 1962; Nobel Prize 1981)

77. stimuli must be positioned appropriately maximal response to stimuli of a particular orientation ±15°. Simple cells receptive fields look like their preferred orientations response rate response rate

84. White light decomposed into s p e c t r a l c o m p o n e n t s  refracted by a prism and split into rays of different wavelengths.  amount of refraction determined by wavelength Newton (with some refinements) Nonetheless, color sensations are related in consistent and measurable ways to physical features of light infrared (not visible) red orange yellow green blue violet ultraviolet (not visible)

85. Complexity or Purity Different wavelengths hue multiple of wavelength saturation brightness Different intensities Amplitude ≈ Intensity Wavelength

87.  : wavelength   : hue You can add pure colors and get one that’s not a spectral color  no characteristic wavelength 530 650 Metamers tell us how to organize the optics : Complementary colors are opposites in some sense 580 460 A color circle, but… 600 O R G B Y ??? P 490 B - G G - Y 490

88. Other experiences suggest organizations more elaborate than a circle  : intensity   : brightness What happens when there is more or less light? What does the color look like? The higher the %white the less saturated a color will look. The higher the % other wavelengths, the less saturated a color will look.  : spectral purity   : saturation blue . . . heather blue . . . gray green . . . heather green . . .gray red . . . pink . . . gray Maximal at moderate intensities only

89. Colors on opposite sides  gray Broadest portion appears at medium lightness. Any cross-section  color wheel for a particular lightness Wavelength + Intensity + Purity  Color experience all colors can be obtained from a few primaries  tells us about the physiology of color perception The Color Solid brightness white black

92. Trichromatic theory not the whole story Color afterimages Color blindness comes in pairs

95. Trichromatic theory not the whole story Color afterimages complementary colors: R - G & B - Y Color blindness comes in pairs

96. Opponent Process Theory: Perhaps outputs of cones are re-coded somewhere into pairs whose members are antagonists (Hurvich & Jameson, 20th Century)  Y Y B R G Y Y B R G 

98. DESIGN OF RETINA TO OPTIC NERVE To Brain light optic nerve fovea retina RODS CONES BIPOLARS GANGLIONS LIGHT LIGHT

99. A NEURAL SYSTEM OF OPPONENT PROCESSES IF + > – , THEN “BLUE” IF – > + , THEN “YELLOW” IF + > – , THEN “RED” IF – > + , THEN “GREEN” + – – CONES GANGLION CONES GANGLION – + + FOR BOTH OPPONENT PROCESS SYSTEMS: IF + = – , THEN “GRAY” (ACHROMATIC)

100. Wavelength info at retinal level; feed into opponency Fits into the overall theme of the perceptual system missing physical detail, restoring lost structure, making things up as it goes along. But it is also an example of the visual system getting what it needs: There is a biological advantage to seeing color. Note: We’ve really been limited to sensations . Perception is still to come. Color coding is a two-stage process. Puzzle: All this happens inside eyes and brain. How do we experience the world as outside?

103. Keep track of vertex-connected surfaces  eliminate those that are inconsistent For complicated—natural—scenes, occlusion is a problem Even if these are identified as cylinders, how do we know they are part of the same object? We need rules about what’s likely. … with what you know about objects  Given experience, assign to S P the S D that is most likely to have caused it. Overcomes problem caused by occlusion corner of front surface not always 3-D corner of one object not always

104. Different neural activity = different forms… HOWEVER… Form (object) recognition still presupposes a solution…an internal representation. Still doesn’t answer the how question. How (where) does perception occur? =

107. What counts as a form or grouping distinct from a background? In general, Simplicity 3-D or 2-D?

109. Of the alternatives allowed by the proximal stimulus… infer the more likely. The Helmholtzian Solution: Use knowledge of which configurations are likely: Principle of maximum likelihood. Make Unconscious Inferences about the world. Contrast detection is not enough  identify which form the edge belongs to ( Pattern recognition presupposes a solution) Figure vs. Ground: What does the edge belong to?

110. Structuralists emphasized identifying primitives as adding or associating sensations… theirs were too subjective, too qualitative Gestaltists emphasized emergent properties or organizing through grouping laws theirs were descriptive, not predictable. But, how it looks ≠ what it is. Form requires further processing. Teacher through your glasses? Teacher in your locket? far near For example, distance matters

111. Pattern recognition = ƒ(distance, size, shape) How do we know both relative distance and absolute distance? Back to Helmholtz and Unconscious Inference How does S P come to indicate a particular S D given that S P is 2-dimensional and, therefore, ambiguous? Reasonably reliable in a Helmholtzian what-is-normal sense is provided by cues RI for large, far objects = RI for small, near objects Is there reasonably reliable structure that might be used to solve Molyneux’s problem? A B C D

113. III. 2 eyes that receive slightly different views:  binocular disparity Left thumb behind, Right thumb in front; Both far away Thumbs close together Amount of disparity indicates relative distance, separation Thumbs far apart Both up close R R L L L R L R

114. Motion Based Cue for Depth: Ever look out the window while riding in a car? Direction of Travel Objects in the foreground move by faster than objects in the background - Very distant objects appear to remain stationary Motion Parallax

121. S P1 ≠ S P2 Percept @ p1 = Percept @ p2 Shape Constancy Ex. II. Perceived Shape is unaffected by perspective p1 p2

122. Appearance is affected by interpretation! Parallelograms look similar in size and shape (one is rotation of other) Shape Perc’d is derived from distance Perc’d Adding distance cues changes inferred shape. percept-percept coupling Manipulate depth cues & assess consequences for Shape Perc’d .

126. Motion Perception Perception Apparent (Stroboscopic) Movement Do we see things as they are because of the proximal stimulus? No Do we see things as they are because of brain states? Yes Or… A temporal property (change over time) is derived from a succession of static retinal images. t 2 t 3 t 1 Physical Event

127. Interpret with respect to likelihoods . Apparent motion of the disk induced by assumption that enclosures don’t move. The same assumption would underlie our experience of non-illusory motion, too. Again, illustrated by an illusion : “induced motion”

130. Shortest-Path Constraint … simplicity again!!!

133. The Phenomena of ATTENTION: Search for the letter ‘c’ 8 8 8 8 8 8 s c z k e t 8 8 8 8 8 8 s k z c f t e s c z k e t s k z c f t e 8 8 8 8 8 8 Stimulus Driven Attention

134. The Phenomena of ATTENTION: Goal Directed – Intentional/Change Blindness Does the number of white T-shirt players change? Any Gorillas???????

135. Movie

136. The Phenomena of ATTENTION: Selective Listening WHAT IS KNOWN ABOUT UNATTENDED? Only physical characteristics (speech like sounds). Not meaning. “ unattended” “ attended” DICHOTIC LISTENING I cannot tell a lie Never kill a snake SHADOWING I cannot tell a lie COCKTAIL PARTY EFFECT Except when important or relevant (e.g. name) The ever present Unconscious at work yet again….

137. Indirect Perspective of Perception Assumes: Both relinquish the responsibility of perception to an “internal”, “mental”, knower… a homunculus … who organizes and isolates cues and compares percepts and representations. Proximal Stimulus Meaningless Sensations Association/Cues Distal Stimulus Incomplete “ Percepts” Incomplete “ Percepts” Perception Unconscious Inferences, information processing, Laws of organization