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Sensation and Perception > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

With the trichromatic theory, what photoreceptors are sensitive to scotopic light levels? scotpic light levels are what kind of light levels?

A

rods

- low light levels

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2
Q

what do all rods contain? Explain what this leads to

A

the SAME type of photopigment = rhodopsin

  • they all have the same sensitivity to various WLs of light
  • problem of univariance makes it impossible to discriminate colors
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3
Q

Explain how the issue with our rods is a hint that color is psychophysical and not physical?

A

At night, the world hasn’t been drained of color. The same mix of WLs that produce color perception during the day exist on a moonlight night, but we fail to see colors cuz only our rods are stimulated.

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4
Q

Photoreceptors sensitive to photopic light levels? what are photopic light levels?

A

cones

- higher, daylight light levels

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5
Q

Cones come in ____ ______?

- Each contain?

A

3 varieties

- Each contain a slightly different photopigment that gives each type of cone a distinctive WL sensitivity

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6
Q

three cone types are named for what?

A

where they peak of their sensitivity lies on the specturm

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7
Q

explain the 3 cones and the colors that go along with them

A
  1. S-cones: sensitive to short WLs (blue)
  2. M-cones: sensitive to middle WLs (green)
  3. L-cones: sensitive to long WLs (red)
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8
Q

Why is it bad to call them “blue, green, red” cones?

A

If all you had were one of them (for ex/ S cones), you’d have the same problem of univariance

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9
Q

define trichromacy

A

the theory that the color of any light is defined in our visual system by the RELATIONSHIPS of three numbers, the outputs of the three cones types

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10
Q

what doesn’t matter in trichromacy? Explain with ex/

A

The INTENSITY of the light doesn’t matter cuz the relationships don’t change
ex/ where you fall on the scale doesn’t matter (33/36 v 73/76) = still a 3 pt difference

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11
Q

cones that respond to smallest range of WLs? what does this mean?

A

s-cones

- they’re stimulated the least

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12
Q

Really, since light if psychophysical, what could you do to cause color to appear?

A

you could just stimulate certain photorecpetors in different ways with no light and make a person see color when nothing is there

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13
Q

color space?
color constancy?
color vision in non-humans?

A

Ch 5 powerpoint - 112

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14
Q

trichromatic theory aka?

A

Young-Helmholtz theory

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15
Q

who came up with the color matching experiment? explain it

A

Maxwell

  • had lights and told ppl to mix light colors together until you get them to look like another set light.
  • discovered that it takes 3 colors to achieve any other color on the electromagnetic spectrum = must be 3 cone types
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16
Q

what did Ewald Hering notice?

  • Give ex/
  • what did this lead to?
A

some color combinations are legal while others are illegal

  • legal: bluish green, reddish yellow (orange), bluish red (purple). illegal: reddish green or bluish yellow
  • Why can’t certain colors mix together? led to opponent processes
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17
Q

define the opponent color theory

A

the theory that perception of color is based on the output of three mechanisms, each of them based on an opponency between two colors: red-green, blue-yellow, and black-white (although this can be grey - different)

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18
Q

what is a unique hue?

A

any of four colors that can be described with only a single color term - red, yellow, green, blue

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19
Q

give examples of non-unique hues

A

purple - reddish blue

orange - reddish yellow

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20
Q

explain the hue cancellation experiment

- give an example

A
  1. start with a color (like yellowish green)
  2. attempt to determine how much of the opponent color of one of the starting color’s components must be added to eliminate any hint of that component from the starting color
    ex/ how much blue must I add to eliminate any hint of yellow?
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21
Q

what is an afterimage?

A

a visual image seen after a stimulus has been removed

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22
Q

what is a negative afterimage?

A

an afterimage whose polarity is opposite to the original stimulus

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23
Q

how do afterimages work with light/dark? colors?

A

light = dark negative afterimage

- colors are complementary: red produces green afterimages, blue produces yellow (& vice versa)

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24
Q

How LGN cells work with opponent processes?

A
  • Some cells are excited by L-cone onset in center, and inhibited by M-cone onsets in surround (& vice versa) (RED v GREEN)
  • some cells are excited by S-cone onset in center, inhibited by (L+M)-cone onsets in their surround (& vicer versa) (BLUE v YELLOW - yellow is between M&L cones)
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25
Q

LGN is _________ of color processing? what does this mean?

A

not the end

- color processing continues in visual cortex

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26
Q

what is achromatopsia? explain in simpler terms

A

an inability to perceive colors that is caused by brain damage
- has nothing to do with eyes - visual system is intact, but your brain (not sure where) doesn’t recognize colors

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27
Q

evidence that people do see color the same way?

A

on tests of hue cancellation, people see unique hues as more or less the same on the white light spectrum (use more or less same mixtures of light to make different colors)

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28
Q

% of males and females who are color blind

A

8% males

0.5% females

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29
Q

what happens if you have two cones types instead of three?

If you have all 3 but one is messed up?

A

the normally 3-D colors space becomes 2-D

- world will still be in color, but you’ll have a “flatter” color experience

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30
Q

list the 6 types of color blindness

A

deuteranope, protanope, tritanope, color-anomalous, cone monochromat, rod monochromat

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31
Q

protanope?

A

due to absence of L cones

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32
Q

deuteranope?

A

due to absence of M cones

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33
Q

tritanope?

A

due to absence of S cones

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34
Q

vast majority of color blindness are what types? aka?

A

deuteranope or protanope, red/green color blindness

35
Q

tritanope is much more ______ and less _______

  • explain why?
  • explain difference between protanope and deuteranope?
A

rare, severe

  • less sever cuz S cones cover a much smaller area of the spectrum
  • see much different shades
36
Q

define color-anomalous color blindness

- reword simpler

A

have 2 types of cones (typically L & M) which are so similar that they can’t make discriminations based on them
- stimulated in such a similar way that the brain can’t distinguish them

37
Q

define cone monochromat

- how do they see?

A

have only one cone type (& rods)

- see in shades of grey, can detect detail and contrast

38
Q

define cone monochromat

- explain why this is so impairing

A

have no cones of any type; truly color-blind and badly visually impaired in bright light

  • rods are only functioning type of cell, so they don’t see color, but they also don’t really see ANYTHING very well (no detail, contrast)
  • they see the world as it would look like if it was always dark
39
Q

ex of how a deuteranope would see different WLs

A

560 & 610 = green & reddish orange for trichromats

- deuteranope can’t tell a difference

40
Q

study Euclidean geometry problem

A

133

41
Q

define metrical depth cue

A

a depth cue that provides quantitative info about distance in the third dimension

42
Q

define nonmetrical depth cue

A

a depth cue that provides info abou the depth order (relative depth) but not depth magnitude

43
Q

be able to define and recognize examples of all monocular depth cues (136-142)

A

study them!
- occlusion, relative size, relative height, texture gradient, familiar size, aerial perspective (haze), linear perspective

44
Q

what is a pictorial depth cue?

A

a cue to distance or depth used by artists to depict 3-D depth in 2-D pictures

45
Q

what is animorphosis?

A

use of the rules of linear perspective to create a 2-D image so distorted that it looks correct only when viewed from a special angle or with a mirror that counters the distortion

46
Q

what are figures 6.18 and 6.19 examples of? p. 144

A

animorphosis

47
Q

define motion parallax

  • What is this used for?

- downside?

A

when you’re moving, images closer to the observer appear to move faster across the visual field (shift position more) than images farther away

  • the brain uses this info to calculate the distance of objects in the environment (how far objects are)
  • works only if head moves (not just eyes)
48
Q

define convergence

A

the ability of the two eyes to turn inward, often used to focus on nearer objects

49
Q

define divergence

A

the ability of the two eyes to turn outward, often used to focus on farther objects

50
Q

the only cues that can tell us the EXACT distance to an object

A

familiar size, convergence/divergence

51
Q

study crayon pics on p. 147 & 149 - binocular disparity

A

study

52
Q

striate cortex location, why impt.

A

at base of skull, part of occipital lobe

- visual info sent here after LNG

53
Q

striate cortex breakdown

- relevant for?

A

sends info 2 diff ways:

  1. ventral (bottom) = what pathway
  2. dorsal (top) = where pathway
    - relevant for motion
54
Q

inferotemporal cortex?

A

activated in response to global form - goes with what portion

55
Q

define motion

A

a change in position over time

56
Q

define apparent motion

A

when you see picture rapidly alternate in succession, it looks like they are moving

57
Q

study bug pics - fig 7.3, p. 171

A

study

58
Q

when do we experience apparent motion?

- explain

A

watching TV, movie, use computer

- animated cartoon = series of stilldrawings

59
Q

when apparent motion won’t work?

A
  • distance = if pics are too far away from each other

- speed = if images are shown too fast or too slow

60
Q

what is the correspondence problem?

A

the problem of the motion detection system in determining which part of Frame 1 corresponds to Frame 2

61
Q

explain the correspondence problem in figure 7.5 on p. 173

A

How does our motion detection system know which circles in frame to correspond to which circles in frame 1?

  • we have motion detectors for ALL directions
  • one detector will sense the diagonal motion from A to C
  • another will sense the vertical motion from A to B
  • these detectors compete to determine overall perception
62
Q

what is the aperture problem?

A

the fact that when a moving object is viewed through an aperture (or receptive field), the direction of motion may be ambiguous

63
Q

explain the aperture problem in figure 7.5 on p. 173

A

a different detector (vertical) wins the competition for overall perception when an object is viewed through an aperture than would win if we could see the whole object (diagonal)

64
Q

how does the aperture problem relate to our visual system? what does this mean?

A

every primary visual cortex neuron sees the world through a small aperture
- none of the VI cells alone can tell with certainty which visual elements correspond to one another when an object moves, even when no mask is present

65
Q

solution to the aperture problem with vision?

A

build in another layer/set of neurons to listen to the V1 neurons and integrate signals that may conflict (p.174)

66
Q

explain the experiment that figured out the medial temporal area’s importance in motion detection

A

they trained monkeys to be able to detect the motion of dots when only 2-3% were moving in a certain direction (and the rest were moving randomly)

  • then they lesioned the MT areas
  • monkeys needed about 10X as much dots to identify direction of motion
  • ability to discriminate orientation of stationary patterns = unimpaired
67
Q

explain the experiment that figured out certain directions involved in the MT cortex

A
  • poked monkey’s MT area and found that groups of neurons respond to motion in different directions
  • if you poke ones that detect rightward motion, monkeys were likely to say they saw rightward motion, even if dots were moving in a different direction
68
Q

the rest of Ch 7? Aftereffects on?

A

maybe study???

69
Q

define attention

A

a very large set of selective processes in the brain

70
Q

define overt attention

- explain simpler

A

directing your senses toward a stimulus

- intentionally directing senses (ex/ looking or listening really hard)

71
Q

define covert attention

  • explain simpler

- give ex/

A

when something captures your focus without your intention

  • not trying to attend to something but you can’t help it
  • ex/ hear a honk, hear someone call your name
72
Q

define divided attention

- give ex/

A

focusing on two things at once

- watching movie and doing HW

73
Q

define sustained attention

  • involved in?

- give ex/

A

focusing on something over a prolonged period of time

  • involved in motivation and vigilence
  • when doing something boring - watching the pot to note when it starts to boil
74
Q

define selective attention

- reword it simpler

A

restricting your processing to a subset of possible stimuli

- trying to focus on one thing and ignoring other things (inhibition)

75
Q

type of attention we’re usually talking about?

A

selective attn

76
Q

are the types of attn mutually exclusive?

A

no - can overlap

77
Q

2 things to note about attention

A

1) it operates in all of our senses

2) we can allocate attention differently in each

78
Q

ex/ of allocating attention differently

A

1) choosing to focus more on music or HW

2) injury doesn’t hurt as much when playing a sport

79
Q 
define salience (2) 
explain simpler
A
  • vividness of stimulus relative to its neighbors
  • standing out conspicuously, prominent, of notable significance
  • **how meaningful a target is to you
  • ex/ show faces of ppl to determine emotions - we respond faster to ppl we know cuz they’re salient to us
80
Q

reaction time? posner’s procedure? p. 191

A

maybe study

81
Q

what is the binding problem in relation to visual search?

  • more generally?
  • give ex/
A
  • We might be able to analyze a collection of basic features in a preattentive stage of processing, but we won’t know how those features are bound together until we attend to the object
  • the challenge of tying together various attributes of a single object, when the attributes are handled by different brain circuits
  • ex/ shape, brightness, color, size of car = different parts of our brain get these features, but we somehow bind them together in our brain to form a whole
82
Q

explain the feature integration theory

A
  • attention is divided into two stages: a preattentive stage and an attention demanding stage (selective attention stage)
  • limited set of basic features (enough for a guided search) can be processed preattentitvely
  • other properties, including the correct binding of features to objects, require attention
83
Q

what happens if you need to attend to something, but you don’t have enough time?

  • Explain in depth
  • examples
A

you might commit an illusory conjunction - false combinations of features from different sources

  • you don’t have enough time or intentional resources to devote to something
  • brain creates a memory of something that was similar to what you saw, but not exactly what you saw
  • Ex/ mixed letter with color that was close to it (p. 200), eye-witness testimony

Sensation and Perception (3 decks)

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