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Foundation of Cognition > Lecture 03 Visual Perception > Flashcards

Lecture 03 Visual Perception Flashcards

1
Q

Perception

A
  • Picking up sensory information from external environment
  • Process into perceptual experience
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2
Q

Human Eye

A
  • Photoreceptors
  • Ganglion cells
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3
Q

Photoreceptors

A
  • Rods
  • Cones
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4
Q

Rod Cells

A
  • Monochromatic
  • Sensitive
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5
Q

Cone Cells

A
  • Colors
  • Sharpness
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6
Q

What are the differences between rod and cone cells

A
  • Distribution
  • Connection
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7
Q

Ganglion Cells

A

Rod convergence: light sensitivity, less acuity

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8
Q

Neural Processing

A

Found early stage in the eyes
- Lateral inhibition
- Edge enhancement

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9
Q

Lateral Inhibition

A

Stimulation of a cell inhibit the activity of neighboring cells

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10
Q

Edge Enhancement

A

Chevreul illusion or staircase illusion

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11
Q

Visual Pathway

A
  1. Retina
  2. Pre-optic tracts: separated left and right eyes
  3. Optic chiasma
  4. Post-optic tracts: combined left and right eyes
  5. Lateral geniculate nuclei (LGN)
  6. Visual cortex
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12
Q

Retinotopic Mapping

A

RETINAL cells correspond to points of
surface of the visual cortex

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13
Q

Receptive field

A

Visual space that correspond to retinal region
- at Fovea

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14
Q

3 Specialized Neurons

A
  • Dot detectors
  • Edge detectors
  • Movement detectors
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15
Q

Parallel Processing

A

Different steps are processed simultaneously
- MT: speed and movement
- V4: share and color

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16
Q

V1 & V2

A

Early stage processing
- Color
- Form

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17
Q

V3

A

Form and shapes but not color

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18
Q

V4

A

Color and line orientation

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19
Q

V5

A

Visual motion

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20
Q

Medial temporal cortex (MT)

A

Speed and movement

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21
Q

Two Visual Pathways

A
  • Ventral
  • Dorsal
22
Q

Ventral Stream

A

Occipital-Parietal: What
- Object identification
- Visual agnosia

23
Q

Dorsal Stream

A

Occipital-Temporal: Where
- Object location
- Visually guided action
- Optic ataxia

24
Q

Visual Agnosia

A

Inability to recognize object
- No difficulty in object orientation or reaching

25
Q

Optic Ataxia

A

Difficulty in reaching
- No object identification

26
Q

Visual Illusions

A

Vision-for-action (how pathway) should not be affected by visual illusions

27
Q

Ebbinghaus illusion

A
  • Verbal judgement → stronger illusion effect
  • Grasping → weaker illusion effect
28
Q

3D object sensitivity

A

Ventral pathways damage doesn’t affect

29
Q

The Holistic Processing of Faces Brain Part

A

TMS on parietal cortex (dorsal) disrupts

30
Q

Color Vision

A
  • Hue – colors
  • Saturation – vividness (amount of white)
  • Brightness (value) – intensity of light-to-drak
31
Q

Color Vision Functions

A
  • Recognize
  • Categorize objects
    E.g., under- or overripe fruits
32
Q

Trichromatic Theory

A
  • Three types of cone receptors
    1) Short-wavelength (blue)
    2) Medium-wavelength (yellow- green)
    3) Long-wave length (orange-red)
  • Perceived color is determined by relative stimulation levels
33
Q

Opponent-process Theory

A
  1. Red-green channel
  2. Blue-yellow channel
  3. Achromatic channel (white-black)
    - Negative afterimage [link] cannot be explained by the trichromatic theory
    - Adaptation of presented color -> higher sensitivity of opponent color in white light
    - Opponent color cannot be seen together (e.g., bluish yellow or reddish green).
    - Color blindness for both color in a channel
34
Q

Color Constancy

A
  • Surface or object is perceived as having the same color when the illuminant (light source) is changed
  • Color perception does not depend solely on the wavelengths of the light
35
Q

Familiarity effect

A
  • Chromatic adjustment method/Chromatic adaptation
  • Over-adjustment
36
Q

Scene Illumination

A
  • Reflected wavelength is influenced by light source
  • Light source estimation is accurate -> High color constancy
  • The Dress: White/gold or blue/black
    1) Ambiguous light source
    2) Depend on how observers assume light source
37
Q

Form Perception: Gestalt Approach

A
  • Perceptual organization principle
  • Figure-ground organization
  • Law of prägnanz (good figure)
  • Innate and intrinsic
38
Q

Organization and Features

A
  1. Bottom-up process
    - Marr’s Computational Approach
    - Biederman’s Recognition-by Components Theory
  2. Top-down process
39
Q

Marr’s Computational Approach

A
  1. Primal sketch – 2-D description
  2. 2.5-D sketch – depth and orientation
  3. 3-D model representation – shape and relative position
40
Q

Biederman’s Recognition-by Components Theory

A

GEON: Basic shapes (geometric ions)

41
Q

Top-down Process

A
  • Incoming signals from cortex to primary visual cortex.
  • Strong effects for ambiguous figures
  • Interactive-iterative framework
42
Q

Depth Perception

A
  • Transformation of 2-D retinal images to 3-D representations.
  • Ambiguous information
  • Cues
43
Q

Cues

A

1) Monocular cues
2) Binocular cues
3) Oculomotor cues

44
Q

Monocular Cues

A

“Pictorial cues”
- Interposition
- Linear perspective
- Familiar size
- Blur
- Texture gradient
- Motion parallax

45
Q

Binocular Cues

A

Binocular disparity
- Stereopsis: ability to perceive in 3-D
- Decrease with distance

46
Q

Oculomotor Cues

A
  • Vergence: Eye Rotation
  • Accommodation: Eye focus
47
Q

Vergence

A

Eye Rotation

48
Q

Accommodation

A

Eye focus

49
Q

Size Constancy

A

Distance -> different retinal images

  • Haber & Levin (2001)
  • Invariant size - e.g., bicycle
  • Variable size - e.g., TV
  • Unfamiliar - e.g., ovals
50
Q

Helmholtz’s theory of unconscious inference

A

Humans unconsciously made inference based on retinal image size and distance

51
Q

Accuracy of Size judgment

A
  • Invariant size > Variable size > Unfamiliar

Foundation of Cognition (7 decks)

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