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PSYCH 20 > LECTURE 5 > Flashcards

LECTURE 5 Flashcards

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1
Q

VISION

A

Construction of the world based on incoming information provided by light interacting with
photoreceptors on the retina.
* Most important/informative sense for humans
* Greatest amount of sensory cortex is devoted to vision
* Conscious experience dominated by visual information

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2
Q

EARLY NOTIFICATION VS RICH DETAIL

A

Tradeoff between accuracy and speed

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3
Q

LIGHT

A

Comprised of photons – particle and wave
* Color (and visibility) of light related to its
wavelength
* Brightness of light related to its amplitude

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4
Q

RETINA

A

Light stimulates photoreceptors at far end of retina
* Neural signals converge onto ganglion cells through bipolar cells
* Ganglion cell axons group into the optic nerve, which projects into brain

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5
Q

RODS

A

Low light vision (scotopic)
* Sensitive to fast motion
* Low resolution; poor edge detection (high convergence)
* Concentrated at peripheries of eye
* ~120 million per eye

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6
Q

CONES

A

Requires bright light (photopic)
* Three types – short, medium, and long – correspond to wavelength most sensitive to
* High resolution; good edge detection (low convergence)
* Concentrated in the fovea (middle of retina; focus point)
* ~6 million per eye

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7
Q

CONES VS RODS

A

Although the rods greatly outnumber the cones, each cone provides a much larger relative input to visual cortex due to neural convergence
* ~90% of brain’s input originates from the cones

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8
Q

DOES RIGHT EYE GO TO LEFT BRAIN AND VICE VERSA?

A

No. Left visual field projects to the right hemisphere of
visual cortex and right visual field projects to the left hemisphere of visual cortex

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9
Q

THROUGH THE BRAIN

A

Information from the optic nerve splits to both hemispheres in the optic chiasm
* Routed through the lateral geniculate nucleus (LGN) in the thalamus
* Projected to primary visual cortex, area V1 in the Occipital lobe

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10
Q

LGN NEURON (THALAMUS) COMPRISED OF

A

Parvo and Magno cells

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11
Q

PARVO CELLS

A
  • Connections from foveal cones
  • Color sensitive
  • Detail and edge detection
  • Good spatial resolution
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12
Q

MAGNO CELLS

A
  • Connections from peripheral rods and cones
  • Sensitive to motion over wide areas
  • Bad spatial resolution
  • “Fast track”
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13
Q

VISUAL CORTEX

A
  • Area V1 (primary visual area)
  • Back of occipital lobe
  • Individual neurons responsive to edges of specific orientations
  • Retinotopic organization
  • Cortical magnification
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14
Q

PARIETAL LOBE PATHWAY

A

Dorsal pathway (spatial location and action)

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15
Q

TEMPORAL LOBE PATHWAY

A

Ventral pathway (characteristics of objects)

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16
Q

COLOR - PHYSICAL AND PERCEPTION DEFINITION

A
  • Physics definition
  • Wavelength of light
  • Can be emitted from a light source or reflected off a surface
  • Perceptual definition
  • Experience of “color”
  • Based on wavelength – but only partially
  • Perceptual experience of color changes based on
    brightness and hue of light source and lightness of object
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17
Q

COLOR MIXING

A

Additive color mixing
* Mixing light
* Every new color “adds” emitted color
* Colors can be defined as a combination of red, green,
and blue (RGB)
* Photoshop RGB color picker

18
Q

CONES AND COLOR

A
  • Three types of cones, corresponds to size of
    wavelength most sensitive to: Short (Blue), Medium (Green) & Long (Red)
  • Combination of information from three cones is
    unique for all visible wavelengths
  • S-cones are less common, and absent in fovea
  • M-cones are a more recent development (cf. dog
    vision)
19
Q

OPPONENT-PROCESS THEORY

A

Color “opposites”
* Red-Green, Blue-Yellow, Black-White
* Color adaptation effect
* Neurons “fatigue” when responding to same stimulus
* When stimulus is removed, “opposite” is perceived

20
Q

COLOR WHEEL

A

Colors opposite from each other are opposing
Opposing colors “pop” when combined = Color contrast

21
Q

BRIGHTNESS

A

Intensity of light; luminance
* Depends on lighting, transient

22
Q

LIGHTNESS

A

Degree to which a surface reflects light;
reflectance
* Quality of an object itself, stable

23
Q

LIGHTNESS CONSTANCY

A

Interplay of lighting and lightness determines brightness (lightness constancy)
* Both a white sheet of paper in a dark room (a) or a grey sheet of paper in a bright room (b) have the same brightness
* Therefore - a must be a lighter surface than b since brightness is the same, but a is viewed with less overall light

24
Q

COLOR CONSTANCY

A

This same process occurs when evaluating the color of objects in different lighting contexts
* Colors reflect different spectrums under different colored lights
* Like lightness constancy, need to figure out the color of the object itself, so need to “subtract” ambient lighting

25
Q

SIZE OF AN OBJECT

A

The size of an object on the retina is determined by
both the size of the object and the distance it is
from the observer.
* To account for this, objects can be measured in terms of visual angle.

26
Q

SCENE

A

External world of objects (3d)

27
Q

IMAGE

A

Light reflected by the scene and picked up
on retina (2d)

28
Q

PROBLEM OF INVERSE OPTICS

A

Theoretically infinite amount of 3d scenes can lead to
same 2d image

29
Q

PROBLEM OF OBJECT INVARIANCE

A

Need to recognize 3d object from all possible 2d images

30
Q

Constructing 3D

A
  • Reconstruct scene from image
  • Monocular depth cues
  • Requires one eye only
  • Can be represented in 2D art/pictures
  • Binocular depth cues
  • Requires both eyes
  • Binocular disparity
  • Slightly different images on each retina due to distance
    between eyes
  • Distance information is provided from both
31
Q

MONOCULAR DEPTH CUES

A

Occlusion: Closer objects occlude objects further away
Proximity to Horizon (Relative height): Distance from object origin to horizon. Closer proximity = further away
Vanishing Point
Ponzo illusion
Relative size: Similar objects appear smaller as they are further away
Relative Height

32
Q

EBBINGHAUS ILLUSION

A
  • Size constancy
  • Size is partially determined by contex
33
Q

FORCED PERSPECTIVE

A

Illusion only works when viewed from a single point/angle of perception.

34
Q

BINOCULAR DEPTH CUES

A

Each eye gets a slightly different view of the visual
field (check it yourself)
* Binocular disparity
* For a given object, the degree of offset is determined
by how far away it is

35
Q

MOTION ADAPTATION EFFECT

A

Neurons get fatigued staring at still image and it starts appearing to move. Apparent motion can even work with random dots – if you prime people to see it or “direct” the motion
Structure from motion
* Rotating objects provide information about 3d shape
* Ballerina illusion

36
Q

MOTION PAREIDOLIA

A

Detecting pattern where there is no real pattern

37
Q

MOTION PARALLAX

A
  • Movement of scene when you are moving
  • Close things move by faster
  • Helps with depth perception
38
Q

TEMPORAL RESOLUTION

A
  • Ability of visual system to separate events over time
  • Flicker fusion – can’t separate, “fuse” together
  • Speed of sight
  • ~ 30 ms (?)
  • But not uniform!
  • Dorsal vs. Ventral (temporal hierarchy)
    our perception of the world lags behind by ~200 millisecond
39
Q

VISIBLE PERSISTANCE

A
  • Sustained activation after stimulus
  • Allows for temporal integration of quickly presented stimuli
  • Movies
  • Animation
  • Light “tracers”
40
Q

MOTION BLUR

A
  • In humans, due to visible persistence
  • In film, due to the way a camera works
  • Not explicitly present in animation!

PSYCH 20 (14 decks)

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