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perception > Problem 6 - DONE > Flashcards

Problem 6 - DONE Flashcards

depth + size perception

1
Q

cue approach to depth perception

A

= explains how we get from the flat image on retina to three-dimensional perception of the scene

  • learn connection between cue + depth through previous experience with environment
  • -> association between particular cues and depth becomes automatic
  • when depth cues are present: perceive three dimensions
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2
Q

different types of depth cues

A
  • oculomotor cues
  • monocular cues
  • binocular cues
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3
Q

oculomotor cues

A

= cues based on ability to sense the position of eyes + tension in eye muscles

  • convergence
  • accommodation
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4
Q

convergence

A

= inward movement of eyes that occurs when we look at nearby objets

(german: schielen)
- -> feel inward movement of eyes that occurs when eyes converge to look at nearby objects

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5
Q

accommodation

A

= change in shape of the lens that occurs when we focus on objects at various distances
–> feel tightening of eye muscles that change shape of lens to focus on nearby object

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6
Q

monocular cues

A

= cues that work with one eye

  • accommodation
  • pictorial cues
  • movement-based cues = sources of depth information created by movement
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7
Q

pictorial cues

A

= sources of depth information in a two-dimensional picture

  • occlusion (any range)
  • relative height (2-30+ metres)
  • relative size (any range)
  • perspective convergence
  • familiar size
  • atmospheric convergence (30+ metres)
  • texture gradient
  • shadows
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8
Q

occlusion

A

= one object is in front of another/one object hides another partially

  • partially hidden object seen as being farther away
  • -> not provide info about object’s distance
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9
Q

relative height

A

= object with its base closer to horizon is usually seen as being more distant

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10
Q

relative size

A

= when two objects are of equal size, the one farther away will take up less of our field of view than the one closer
–> depends on knowledge of physical sizes

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11
Q

perspective convergence

A

= when looking down parallel lines that appear to converge in distance

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12
Q

familiar size

A

= used when judging distance based on prior knowledge of size of objects
–> most effective: other depth information is absent

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13
Q

atmospheric convergence

A

= when distant objects appear less sharp, with a slight blue tint (than nearer objects)

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14
Q

texture gradient

A

= elements equally spaced in scene appear to be more closely packed as distance increases
- increased fineness of texture in distance: enhances perception of depth

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15
Q

shadows

A

= decreases in light intensity caused by blockage of light

–> provide info about location of objects

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16
Q

motion-produced cues

A

= emerge when we start moving

  • motion parallax (0-20 metres)
  • deletion and accretion (0-20 metres)
17
Q

motion parallax

A

= when, as we move, nearby objects appear to glide rapidly past us, more distant objects appear to move more slowly
–> image of object closer to us move farther across retina (than objects farther away)

18
Q

deletion and accretion

A

= as observer moves sideways, some things become covered (= deletion) and others become uncovered (= accretion)

19
Q

binocular cues

A

= stereoscopic depth perception = cues that depend on both eyes

  • stereoscopic vision = two-eyed depth perception
  • -> involves mechanisms that take into account differences in the images formed on the left and right eyes
20
Q

binocular disparity

A

= differences in images on the left and right retinas

  • -> basis of stereopsis
  • corresponding retinal points
21
Q

absolute disparity

A

= degree to which objects deviate from falling on corresponding points
–> measuring angle of disparity

types of disparities:

  • uncrossed disparity = behind horopter (far objects)
  • crossed disparity = in front of horopter (near objects)
  • -> cross your eyes to fixate on point that is closer than horopter (schielen)
22
Q

angle of disparity

A

angle of disparity = amount of absolute disparity; angle between corresponding and non-corresponding retinal points (where it would be located, where it is actually located)
- located on corresponding point = 0
- located on non-corresponding points = non-zero degree
–> provides information object’s distance from horopter
(greater angles of disparity = greater distances from horopter)

23
Q

relative disparity

A

= difference in absolute disparities of objects

  • -> helps indicate where objects in a scene are located relative to one another
  • remains the same as observer looks around scene
24
Q

absolute vs. relative disparity

A
  • absolute disparity: disparity of projections of one object

- relative disparity: difference between disparities of projections of two objects

25
Q

correspondence problem

A

which points in the images on the left and the right retina belong to each other?
- compare images on left/right retina –> calculate amount of disparity
‘distance cues’
- uniqueness = features in the world will be represented once in each retinal image
- continuity = neighbouring points in the world lie at similar distances from the viewer (except at the edges)

26
Q

physiology of binocular depth perception

A

pictorial cues:
- mostly what stream
- V2 neurones (occlusion)
stereopsis:
- binocular depth cells (disparity-selective cells) = neurone that respond best to binocular disparity
–> V1, 2, 5 neurones
neurones in higher visual system:
- primary receiving area: sensitive to absolute disparity
- temporal lobe/other areas: sensitive to relative disparity

27
Q

disparity tuning curves

A

= indicate neural response that occurs when stimuli presented to the left and right eyes create different amounts of disparity

28
Q

perceiving size

A
  • relation between perceiving size and perceiving depth = size-distance scaling
  • -> perception of size can be affected by perception of depth
29
Q

size-distance scaling (formula)

overview lecture

A

S = K * (R * D)
=> object’s perceived size (S) depends on the size of retinal image (R) times the perceived distance (D) and times a constant (K)
{R = size of the image that you view on your retina}
=> D becomes larger = S becomes larger
–> explains why object perceived further away, seem larger (image with two giants/balls)

30
Q

size constancy

A

= perception of object’s size is relatively constant even when we view object from different distances
–> size-distance scaling

31
Q

visual illusions of size

müller-lyer illusion

A

= right vertical line appears longer than left vertical line (even if they are the same)

  • misapplied size constancy scaling: mechanisms that help us perceiving in 3-D world sometimes create illusions when applied to objects drawn on 2-D surface
  • -> fins on right line: appears like inside corner of room
  • -> fins on left line: appears like corner viewed from outside
  • -> size-distance scaling: (R) remains the same, (D) is larger, (S) is determined by perceived distance
  • conflicting cues theory: perception of line length depends on (1) actual length of vertical lines + (2) overall length of figure
  • -> overall length of right figure: larger –> vertical line appears larger
  • -> rejection of idea: depth information is involved in determining illusions
32
Q

visual illusions of size

ponzo illusion

A

= the animal on top appears longer, although animals are the same size on page + have same visual angle

  • misapplied size constancy scaling: depth information provided by converging railroad tracks making the top animal appear farther away –> top animal appears bigger
  • -> scaling mechanism corrects for this increased depth
33
Q

visual illusions of size

ames room

A

= causes two people of equal size to appear very different in size

  • reason: construction of room (shaped that left corner is almost twice as far from observer as right corner) –> woman on left: much smaller visual angle
  • -> size-distance scaling: (D) remains same, (R) smaller for woman on left, therefore, (S) is smaller
  • other factors: relative size: perception of size of two women is determined by how they fill distance between bottom and top of room}
34
Q

visual illusions of size

moon illusion

A

= moon on horizon appears much larger than when it is higher in the sky

  • constant visual angle: moon’s physical size + distance from Earth remain the same
  • apparent distance theory: moon on horizon: appears more distant because it is viewed across filled space of terrain (contains depth information) + moon higher in sky: appears less distant because it is viewed through empty space, with little depth information
  • -> size-distance scaling: (R) remains same, (D) is larger for moon on horizon, (S) is larger
  • angular size contrast theory: moon appears smaller when surrounded by larger objects
  • other factors: atmospheric convergence, colour, oculomotor factors

perception (9 decks)

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