Problem 6 - DONE

Question 1

cue approach to depth perception

Answer 1

= 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

Question 2

different types of depth cues

Answer 2

• oculomotor cues
• monocular cues
• binocular cues

Question 3

oculomotor cues

Answer 3

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

• convergence
• accommodation

Question 4

convergence

Answer 4

= 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

Question 5

accommodation

Answer 5

= 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

Question 6

monocular cues

Answer 6

= cues that work with one eye

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

Question 7

pictorial cues

Answer 7

= 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

Question 8

occlusion

Answer 8

= 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

Question 9

relative height

Answer 9

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

Question 10

relative size

Answer 10

= 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

Question 11

perspective convergence

Answer 11

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

Question 12

familiar size

Answer 12

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

Question 13

atmospheric convergence

Answer 13

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

Question 14

texture gradient

Answer 14

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

Question 15

shadows

Answer 15

= decreases in light intensity caused by blockage of light

–> provide info about location of objects

Question 16

motion-produced cues

Answer 16

= emerge when we start moving

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

Question 17

motion parallax

Answer 17

= 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)

Question 18

deletion and accretion

Answer 18

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

Question 19

binocular cues

Answer 19

= 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

Question 20

binocular disparity

Answer 20

= differences in images on the left and right retinas

• -> basis of stereopsis
• corresponding retinal points

Question 21

absolute disparity

Answer 21

= 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)

Question 22

angle of disparity

Answer 22

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)

Question 23

relative disparity

Answer 23

= 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

Question 24

absolute vs. relative disparity

Answer 24

• absolute disparity: disparity of projections of one object

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

Question 25

correspondence problem

Answer 25

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)

Question 26

physiology of binocular depth perception

Answer 26

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

Question 27

disparity tuning curves

Answer 27

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

Question 28

perceiving size

Answer 28

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

Question 29

size-distance scaling (formula) overview lecture

Answer 29

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)

Question 30

size constancy

Answer 30

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

Question 31

visual illusions of size müller-lyer illusion

Answer 31

= 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

Question 32

visual illusions of size ponzo illusion

Answer 32

= 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

Question 33

visual illusions of size ames room

Answer 33

= 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}

Question 34

visual illusions of size moon illusion

Answer 34

= 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