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psy4051 - examen 1 > Cours #3 > Flashcards

Cours #3 Flashcards

1
Q

Quels sont les deux types d’indices oculomoteurs dans la perception de profondeur?

A

L’accommodation et la convergence

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2
Q

Qu’est-ce que l’accommodation?

A

Contraction des muscles ciliaires (soutiennent le cristallin) associée aux changements de courbure du cristallin. Nous ressentons leur contraction.

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3
Q

Qu’est-ce que la convergence?

A

Sensation de l’angle de convergence oculaire. Nous sentons le mouvement des yeux.

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4
Q

Disparité binoculaire: Qu’est-ce que l’horoptère?

A

Arc imaginaire, passant par le point de fixation (P), sur lequel les objets forment une image sur des points correspondants sur les deux rétines.

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5
Q

Qu’est-ce que la disparité binoculaire?

A

Différence entre les images rétiniennes due aux angles oculaires différents entre les deux yeux, qui sont séparés d’environ 6 cm chez l’humain adulte. C’est la disparité ou la différence sur les rétines qui donnera lieu à la stéréopsie.

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6
Q

Qu’est-ce que la stéréopsie?

A

Perception de profondeur induite par la disparité binoculaire

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7
Q

Qu’est-ce que la présentation stéréoscopique?

A

Dispositif permettant de présenter 2 stimuli dichoptiquement. Il existe des stéréoscopes à miroirs et des stéréoscopes à prismes.

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8
Q

Il existe deux sortes de stéréoscopes. Quelles sont-elles?

A
  • stéréoscope à miroirs (Wheatstone, 1838)
  • stéréoscope à prismes (Brewster, 1849)
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9
Q

Quand a eu lieu le premier visionnement d’un film 3D aux états-unis?

A

en 1952

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10
Q

Qu’est-ce que la disparité absolue?

A
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11
Q

Qu’est-ce que la disparité relative?

A
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12
Q

Qu’est-ce que l’anaglyphe?

A

présentation superposée de 2 images disparates de couleurs différentes, et filtrage de ces couleurs par l’oeil gauche et l’oeil droit (possible avec lunettes 3D - elles simulent la réalité de la profondeur)

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13
Q

Est-ce que la reconnaissance de la forme est nécessaire pour le traitement de la disparité binoculaire?

A

Non, la reconnaissance monoculaire n’est pas nécessaire (pas besoin de reconnaitre la forme pour avoir une perception stéréoscopique)

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14
Q

Qui a permis la découverte du fait que la reconnaissance de la forme n’est pas nécessaire pour le traitement de la disparité binoculaire? Comment?

A

Bela Julesz, 1971
Au départ, il y avait deux patrons identiques faits avec des petits points noirs. Sur l’un d’eux, une translation d’une région a été effectuée, créant ainsi une disparité entre les deux patrons. Malgré le fait qu’aucune forme ne puisse être reconnue dans le “pattern” de points, il est tout de même possible d’avoir un effet tridimensionnel

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15
Q

Où se trouvent les premières cellules binoculaires?

A

Dans la troisième couche du cortex visuel

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16
Q

Comment est organisée la sélectivité à la disparité binoculaire dans l’aire V5 (dorsal)?

A

Il y a des colonnes de sélectivité à la direction du mouvement.
- disparité croisée (proche) = vert
- disparité non-croisée (loin) = rouge

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17
Q

Indice monoculaire de type pictural: qu’est-ce que l’occlusion?

A

recouvrement spatial d’un objet par un autre. la distance perçue de l’objet recouvert est supérieure à celle de l’objet en premier plan

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18
Q

Quel est l’indice monoculaire de type pictural le plus primitif?

A

L’occlusion (on voit que c’était présent dans les dessins faits dans les grottes en - 30 000)

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19
Q

Indice monoculaire de type pictural: qu’est-ce que le gradient de luminance?

A

l’occlusion d’un objet par l’ombre d’un autre objet constitue un indice sur leur distance relative.
Les ombres et lumières créent des effets de relief

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20
Q

Vrai ou faux: le cerveau prend pour acquis que la lumière vient toujours du haut

A

vrai

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21
Q

Indice monoculaire de type pictural: Qu’est-ce que le gradient de texture?

A

La texture change en fonction de la distance. Lorsque c’est près, on voit bien les détails; lorsque c’est loin, on voit moins bien les détails et les éléments semblent de plus en plus rapprochés
(ex photo de coureurs; en avant de la photo on voit quelques coureurs seulement alors qu’en arrière il y en a beaucoup)

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22
Q

Indice monoculaire de type pictural: Qu’est-ce la taille relative?

A

Si les objets ont la même taille réelle, la distance d’un objet est inversement proportionnelle à la surface rétinienne qu’il couvre (plus grand = plus proche, plus petit = plus loin). En d’autres mots, plus la distance augmente, plus la surface rétinienne occupée par l’objet est petite.

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23
Q

Indice monoculaire de type pictural: qu’est-ce que la hauteur relative?

A

La distance perçue est inversement proportionnelle à sa distance, en hauteur, par rapport à l’horizon dans la scène visuelle.
Plus l’objet est près de la ligne d’horizon, plus il est loin (et paraît petit). C’est ce qui explique pourquoi les nuages qui sont le plus bas dans l’image sont plus petits et semblent plus loin

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24
Q

Indice monoculaire de type pictural: Qu’est-ce que la perspective linéaire?

A
  • les lignes parallèles semblent converger au loin (chemin de fer)
  • la distance perçue d’un objet est inversement proportionnelle à sa distance par rapport à un point de fuite.
    (plus les segments s’éloignent vers un point de fuite, plus ils se rapprochent sur la rétine et donnent l’impression qu’ils convergent)
    *La perspective linéaire et les points de fuite sont beaucoup utilisés dans les tableaux pour donner un effet de profondeur (aujourd’hui très utilisé pour faire des illusions dans les rues)
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25
Q

Indice monoculaire de type pictural: Qu’est-ce que la perspective atmosphérique?

A
  • la distance perçue d’un objet augmente si l’objet parait flou et bleuté
    (la matière solide et liquide en suspension donne une apparence floue et bleutée)
    *l’efficacité de cet indice de perception de la profondeur est propre à l’atmosphère terrestre.
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26
Q

Indice monoculaire de type pictural: Qu’est-ce que la familiarité de l’objet?

A
  • La distance d’un objet sera évaluée en fonction de sa taille réelle connue (traitement descendant/top-down)
  • La distance évaluée est relative à la distance d’un objet de référence dont la taille est connue.
    *Cet indice en d’autant plus efficace en l’absence d’autres indices de perception de la profondeur
    ex: gousse d’ail vs chou-fleur. Même grandeur sur l’écran = même grandeur sur la rétine. Notre cerveau trouve ça bizarre parce qu’on sait que le chou-fleur est naturellement plus gros. La seule explication que notre cerveau trouve est qu’il doit être plus loin.
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27
Q

Indice monoculaire de type cinétique: Qu’est-ce que le parallaxe du mouvement?

A
  • Les objets dont la distance est au-delà du point de fixation semblent se déplacer à basse vitesse (plus petit déplacement sur la rétine) dans la même direction que le mouvement de l’observateur.
  • Les objets dont la distance est en-deça du point de fixation semblent se déplacer à haute vitesse (grand déplacement sur la rétine) dans la direction opposée à celle du mouvement de l’observateur
    (ex: quand on roule en auto)
    *plus grand déplacement rétinien = plus grande vitesse et vice-versa.
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28
Q

Vrai ou faux: des objets de tailles différentes peuvent avoir le même angle visuel

A

Vrai

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29
Q

Indice monoculaire de type cinétique: Qu’est-ce que la constance de la taille perçue de l’objet?

A
  • la taille d’un objet parait constante même si la surface rétinienne qu’il couvre change avec la distance
  • ainsi, la surface rétinienne n’est PAS un indice fiable sur la taille de l’objet
  • la distance perçue de l’objet, qui nécessite la perception de la profondeur, DOIT être considérée
    ex: le prof semble toujours faire 5 pieds 8 même s’il est plus proche ou plus loin
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30
Q

Vrai ou faux: la taille perçue d’un objet dépend de sa distance perçue.

A

Vrai.
Plus spécifiquement, la taille perçue d’un objet est proportionnelle à la surface rétinienne qu’il couvre ET à sa distance perçue.

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31
Q

Quelle est la formule qui permet de calculer la taille perçue?

A

T = k (R x D)
T: taille perçue de l’objet
R: surface rétinienne couverte par l’objet
D: distance perçue de l’objet
k: constante

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32
Q

Qu’est-ce que la loi de Emmert?

A

La taille perçue d’une image consécutive est proportionnelle à sa distance perçue.

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33
Q

Qu’est-ce que l’illusion de Muller-Lyer?

A

La ligne semble plus courte ou plus longue en fonction de l’orientation des deux lignes au bout

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34
Q

Qu’est-ce qui pourrait expliquer pourquoi la lune semble toujours plus grosse lorsqu’elle est à l’horizon vs quand elle est au zenith (au dessus de nous)?

A

La distance perçue à l’horizon est supérieure à la distance perçue du ciel
T = k (R x D)
(sur la ligne d’horizon, on a plus d’indices qui nous permettent de l’interpréter comme étant plus loin. Dans le ciel, on n’a pas de référent donc le cerveau sous-estime la taille ou la distance de l’objet)

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35
Q

Qu’est-ce que l’illusion de Ponzo?

A

Les marmottes sur le chemin de fer.
Celle d’en haut semble plus haut que celle d’en bas alors qu’elles sont de la même grandeur.
- according to Gregory’s misapplied scaling explanation, the top animal appears bigger because of depth information provided by the converging railroad tracks that make the top animal appear farther away. Thus, just as in the Muller-Lyer illusion, the scaling mechanism corrects for this apparently increased depth (even though there really isn’t any, because the illusion is on a flat page), and we perceive the top animal to be larger.

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36
Q

Qu’est-ce que l’illusion de la chambre de Ames? How can it be explained?

A

La taille perçue des 2 individus diffère, car la distance perçue des 2 individus est la même mais la taille diffère.
- the construction of the room causes the woman on the left to have a much smaller visual angle than the one on the right.
- we think that we are looking into a normal rectangular room at two women who appear to be at the same distance, so we perceive the one with the smaller visual angle as shorter.
- we can understand why this occurs by returning to our size-distant scaling equation, S = R x D. Because de perceived distance is the same for the two women, but the size of the retinal image (R) is smaller for the woman on the left, her perceived size (S) is smaller.
- another explanation is based on relative size, which states that our perception of the size of the two women is determined by how they fill the distance between the bottom and top of the room. Because the woman on the right fills the entire space and the one on the left only a little of it, we perceive the right one as taller

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37
Q

What’s the idea behind oculomotor cues?

A

the idea behind these cues is that we can feel the inward movement of the eyes that occurs when the eyes converge to look at nearby objects, and we feel the tightening of eye muscles that change the shape of the lens to focus on a nearby object.
The feelings we experience as we move our fingers closer are caused by
1) the change in convergence angle as our eye muscles cause our eyes to look inward
2) the change in the shape of the lens as the eye accommodates to focus on a near object

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38
Q

What are convergence and accommodation useful for?

A

to indicate when an object is close

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39
Q

Convergence and accommodation indicate when an object is close and are useful up to a distance of __________

A

about arm’s length

40
Q

Which oculomotor cue is the most effective?

A

convergence

41
Q

What are the 3 types of monocular cues?

A
  • accommodation
  • pictorial cues
  • movement-based cues
42
Q

What are pictorial cues?

A

pictorial cues are sources of depth information that can be depicted in a picture

43
Q

What are the 8 pictorial cues?

A
  • occlusion
  • relative height
  • relative size
  • perspective convergence
  • familiar size
  • atmospheric perspective
  • texture gradient
  • shadows
44
Q

True or false: occlusion provides information about an object’s distance.

A

False!
Occlusion does not provide information about an object’s distance. It indicates that the object that is partially covered is farther away than another object.
BUT: from occlusion alone, we can’t tell how much farther.

45
Q

According to the cue of ________, objects with their bases closer to the horizon are usually seen as being more distant.
What does this mean?

A

relative height.
this means that being higher in the field of view causes objects on the ground to appear farther away, whereas being lower in the field of view causes objects in the sky to appear farther away.

46
Q

Explain the cue of relative size.

A

according to the cue of relative size, when two objects are of equal size, the one that is farther away will take up less of your field of view than the one that is closer.
the cue depends, to some extent, on a person’s knowledge of physical sizes.

47
Q

When you look down parallel railroad tracks that appear to converge in the distance, which monocular cue are you experiencing?

A

Perspective convergence

48
Q

Which monocular cue was used by Renaissance artists to add the impression of depth in their paintings?

A

Perspective convergence
Ex: Pietro Perguno’s painting.
(this painting also uses relative size)

49
Q

When do we use familiar size?

A

when we judge distance based on our prior knowledge of objects.
ex: Epstein’s experiment (avec les sous) - ne fonctionne pas avec les deux yeux ouverts.

50
Q

When is the cue of familiar size most effective?

A

when other information about depth is absent

51
Q

Explain the atmospheric perspective cue

A
  • it occurs when distant objects appear less sharp than nearer objects and often have a slight blue tint
  • the farther awat an object is, the more air particles (dust, water droplets, airborne pollution) we have to look through, making objects that are farther away look less sharp and bluer than close objects.
52
Q

True or false: the reason that farther objects look bluer is related to the reason the sky appears blue.

A

True

53
Q

The affirmation “elements that are equally spaced in a scene appear to be more closely packed as distance increases” refers to which pictoral cue?

A

Texture gradient.
The increasing fineness of texture as distance increases enhances the perception of depth.

54
Q

True or false: In addition to providing information about the location of objects, shadows also enhance the three-dimensionality of objects

A

True

55
Q

What are the two motion-produced cues?

A
  • motion parallax
  • deletion and accretion
56
Q

What is motion parallax? How does it occur?

A
  • Motion parallax occurs when, as we move, nearby objects appear to glide rapidly past us, but more distant objects appear to move more slowly
  • We can understand how motion parallax occurs by noting how the image of a near object and a far object move across the retina as an eye moves from position 1 to position 2 without rotating.
  • Because the image of a near object travels a larger distance across the retina than a farther object in the same amount of time, it appears to move rapidly
57
Q

Which cue is one of the most important sources of depth information for many animals?

A

motion parallax

58
Q

Which cue is widely used to create an impression of depth in cartoons and video games?

A

motion parallax

59
Q

The affirmation “as an observer moves sideways, some things become covered, and others become uncovered” refers to which motion-produced cue?

A

deletion and accretion

60
Q

When does “deletion” occur? When does “accretion” occur?

A
  • In the exemple, deletion occurs when your left hand seems to be covering your right hand when you move your head to the left.
  • In the exemple, accretion occurs when the far hand is uncovered by moving your head back to the right.
61
Q

True or false: when we see 2-D movies with both eyes, we do not use binocular depth information

A

True. Because the screen is flat, both eyes receive essentially the same images. Thus, any depth perceived in these movies results from monocular or pictorial depth cues.

62
Q

What is binocular disparity?

A

the differences in the images on the left and right retinas. it is the basis of the stereoscopic vision.

63
Q

What are corresponding retinal points?

A

points on the retina that overlap if the eyes are superimposed on each other

64
Q

True or false: the images of objects that are on the horopter fall on corresponding points.

A

true

65
Q

True or false: whatever a person is looking at directly falls on corresponding points, and some other objects fall on corresponding points as well.

A

True (if the other objects are on the horopter)

66
Q

What is absolute disparity?

A

The degree to which objects deviate from falling on corresponding points.

67
Q

True or false: the angle of disparity is greater for objects at greater distances from the horopter.

A

True
greater angles of diparity = greater distances from the horopter

68
Q

What is relative disparity?

A

the difference in absolute disparities of objects in a scene.

69
Q

True or false: relative disparity remains the same as an observer looks around a scene

A

true

70
Q

What is relative disparity useful for?

A

relative disparity helps indicate where objects in a scene are located relative to one another.

71
Q

What is stereopsis?

A

the impression of depth that results from information provided by binocular disparity

72
Q

How do 3-D movies work?

A

The left-eye and right-eye images are presented superimposed on the screen, slightly displaced from one another, to create disparity.

73
Q

what is lenticular projection?

A

when the screen is coated with a film that contains two sets of lenses that direct different images to the left and right eyes (eg: postcards)
- does not require glasses

74
Q

Who created the random-dot strereogram?

A

Bala Julesz (1971)

75
Q

How does the visual system match the parts of the images in the left and right eyes that correspond to one another? In other words, how does the visual system match up the images in the two eyes?

A

This is called the correspondance problem (it has not yet been fully explained)

76
Q

How do we call neurons that respond to absolute disparity?

A

These neurons are called binocular depth cells or disparity-selective cells.
A given cell responds best when stimuli presented to the left and right eyes create a specific amount of absolute disparity

77
Q

Where are neurons sensitive to absolute disparity found?

A

in the primary visual receiving area

78
Q

Where are neurons sensitive to relative disparity found?

A

in the temporal lobe and other areas.

79
Q

True or false: apparently, depth perception involves a number of stages of processing, beginning in the primary visual cortex and extending to many different areas in both the ventral and dorsal streams.

A

True

80
Q

True or false: disparity-selective neurons are responsible for stereopsis.

A

True.

81
Q

True or false: our perception of size can be affected by our perception of depth.

A

True

82
Q

The idea that we can misperceive size when accurate depth information is not present was demonstrated in a classic experiment by ______ and _______.

A

A.H Holway and Edwin Boring (1941)

83
Q

What is visual angle?

A

Visual angle is the angle of an object relative to the observer’s eye.

84
Q

What does the visual angle depend on?

A

the visual angle depends both on the size of the stimulus and on its distance from the observer.

85
Q

What does the visual angle tell us?

A

it tells us how large the object will be on the back of the eye.

86
Q

True or false: a small object that is near and a larger object that is far can have the same visual angle.

A

true. (visual angle depends both on the size of the stimulus and on its distance from the observer)

87
Q

What does Holway and Boring’s experiment demonstrate?

A

the results of this experiment indicate that size estimation is based on the actual sizes of objects when there is good depth information, but that size estimation is strongly influenced by the object’s visueal angle when depth information is eliminated.

88
Q

What is an example of size perception that is determined by visual angle?

A

Our perception of the sizes of the sun and the moon, which, by cosmic coincidence, have the same visual angle (0.5 degrees).
Even though these two celestial bodies are vastly different in size, we perceive them to be the same size because, as we are unable to perceive their distance, we base our judgment on their visual angle.

89
Q

What is size constancy?

A

The fact that our perception of an object’s size is relatively constant even when we view the object from different distances (exemple de la grandeur du prof)

90
Q

Is size constancy decreased under conditions of poor depth information?

A

Yes! (exemple des sous quand on ferme un oeil)

91
Q

How does Richard Gregory explains the Muller-Lyer illusion?

A
  • he explains it on the basis of a mechanism called “misapplied size constancy scaling”.
  • According to Gregory, the lines appear to be at different distances because the fins on the right line (the one that looks longer) make this line look like part of an inside corner of a room, whereas the other line make this line look like part of a corner viewed from outside.
  • because inside corners appear to “recede” and outside corners “just out”, our siz-distance mechanism treats the inside corner as if it is farther away, so the D in the equation is larger and this line therefore appears longer.
  • according to him, it is not necessary that you be consciously aware that these lines can represent three-dimensional structures; your perceptual system unconsciously takes the depth information contained in the Muller-Lyer figures into account, and your size-distance scaling mechanism adjusts the perceived sizes of the lines accordingly
92
Q

Who proposed the conflicting cues theory?

A

R.H. Day

93
Q

What is the conflicting cues theory?

A

this theory states that our perception of line length depends on two cues:
1) the actual length of the vertical lines
2) the overall length of the figure.
According to him, these two conflicting cues are integrated to form a compromise perception of length.

94
Q

What does the apparent distance theory have to say about the moon illusion?

A

according to this theory, the moon on the horizon appears more distant because it is viewed across the filled space of the terrain, which contains depth information; but when the moon is higher in the sjy, it appears less distant because it is viewed through empty space, which contains little depth information.
Because the horizon moon and the elevated moon have the same visual angle but the horizon one appears farther, it appears larger ( S = R x D)

95
Q

Aside from the apparent distance theory, what is another theory of the moon illusion? What does it say?

A

The angular size contrast theory
It states that the moon appears smaller when it is surrounded by larger objects. Thus, when the moon is elevated, the large expanse of sjy surrounding it makes it appear smaller. However, when the moon is on the horizon, less sky surrounds it, so it appears larger.

96
Q

Animals with lateral eyes such as the rabbit cannot use disparity to perceive depth. Why is that?

A

To make use of binocular disparity, an animal must have eyes that have overlapping visual fields. Since animals with lateral eyes do not have overlapping visual fields, they cannot use disparity to perceive depth.

97
Q

What is insects’ most important method of judging distance?

A

movement parallax.

psy4051 - examen 1 (4 decks)

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