Task 6: Three dimensions

Question 1

Types of cues to perceive depth

Answer 1

Oculomotor cues
Monocular cues
Binocular cues

Question 2

Oculomotor cues

Answer 2

• position of the eyes and tension in eye muscle

- created by convergence and accommodation

Question 3

Most effective oculomotor cue

Answer 3

convergence - inward movement of the eyes that occurs when we look at nearby objects

Question 4

Monocular cues

Answer 4

• cues that work with one eye

- include accommodation, pictorial cues and motion-related cues

Question 5

Pictorial cues

Answer 5

Occlusion (V2 neurons) = one objects is hidden (partially) by the other

Relative size = two objects are the equal size but the one further away will take up less of our visual field

Familiar size = knowledge of size

Texture gradient = parallel lines appear more closely packed as distance increases

Relative height = closer to horizon means more distant

Perspective convergence = parallel lines converge in distance

Atmospheric perspective = further away => less sharp and bluish

Shadows

Question 6

Motion-produces or movement-related cues

Answer 6

work once we start moving

• motion parallax
• deletion
• accretion

Question 7

Motion parallax

Answer 7

image of objects closer to us move farther across the retina => nearby objects appear to glide rapidly past us / distant objects move more slowly

Question 8

Deletion and accretion

Answer 8

• observer moves sideways
  => thing becomes covered = deletion
  thing becomes uncovered = accretion

Question 9

Binocular cues

Answer 9

• cues that relies information from both eyes and leads to binocular disparity

Question 10

Stereoscopic vision

Answer 10

impression of depth that results from information provided by binocular disparity

Question 11

Binocular disparity

Answer 11

differences between two retinal images of the same scene

Question 12

Binocular disparity relies on

Answer 12

Corresponding and non-corresponding retinal points

Question 13

Corresponding retinal points

Answer 13

• points on the retina that overlap if eyes are superimposed on each other = zero disparity => horopter

Question 14

Horopter

Answer 14

• surface of zero disparity

- point of focus

Question 15

Non-corresponding retinal points

Answer 15

• surface of non-zero disparity
• objects that are not on the horopter
• absolute disparity
• relative disparity

Question 16

Absolute disparity

Answer 16

• primary receiving area
• one object
• degree to which the object deviates from falling on corresponding points/horopter (measuring angle)
• crossed or uncrossed disparity

Question 17

Greater angle of absolute disparity

Answer 17

indicates greater distance of the object from the horopter

Question 18

Crossed disparity

Answer 18

• object in front of the horopter
• right eye => object appears to be displaced to the right
• left eye => object appears to be displaced to the left

Question 19

Uncrossed disparity

Answer 19

• object behind the horopter
• right eye => object displaced to the left
• left eye => obj. displaced to the right

Question 20

Relative disparity

Answer 20

• temporal lobe
• difference between the absolute disparities of projections of two objects
• indicate where objects in a scene relative to one another

Question 21

Visual processing of stereopsis in the brain

Answer 21

messages from V2 (contours) must be fed back to V1 (disparity) to modulate processing of smaller features

Question 22

Correspondence problem

Answer 22

• how to match images on the left and right retinas

Question 23

Constrains to “solve” the correspondence problem

Answer 23

1. uniqueness = feature is represented exactly once one each retinal image
2. continuity = neighbouring points lie at similar distances from the viewer

Question 24

Experiments like selective rearing (cats alternating vision between two eyes) and Microstimulation (monkeys) demonstrated that

Answer 24

eliminating disparity-selective neurons elimintaes stereopsis => responsible for depth perception

Question 25

Perception of size can be affected by

Answer 25

our perception of depth

Question 26

Holway and Boring experiment

Answer 26

we can misperceive size when accurate depth information is not present

Question 27

Visual angle

Answer 27

- extending lines lens to the object - depends on the size of the stimulus and distance from the observer - object is closer => visual angle and retinal image become larger - small objects near and larger objects far can have the same visual angle

Question 28

Size distance scaling formula

Answer 28

S = K (R x D) ``` S = perceived size of the object R = size of retinal image D = perceived distance ```

Question 29

If X goes further away from us, the size of retinal image R becomes smaller, therefore

Answer 29

perception of X's distance D becomes larger | => a balance is created between R and D, so S (size of X) remains the same

Question 30

Emmert's law

Answer 30

- the farther away an afterimage appears, the larger it will seem - if R remains the same and D increases => S seems larger

Question 31

Muller-Lyer illusion

Answer 31

- equal vertical lines seem to have different lengths | - R remains the same and D is larger => S is determined by D

Question 32

Ponzo illusion

Answer 32

- animal on the top of the page appears longer - converging railroad tracks - D is larger => S is larger

Question 33

Ames room

Answer 33

- people of equal size appear different in size since they are in different corners of the room - perceived distance D is the same but R is smaller for person X => therefore the size S of X is smaller

Question 34

Moon illusion

Answer 34

- moon on horizon appears much larger | - R is the same, D is large when the moon is on the horizon => S is larger