problem 5 - depth perception

Question 1

3 types of cues to depth

Answer 1

1. Oculomotor: cues based on our ability to sense the position of our eyes and the tension in our eye muscles (convergence & accomodation)
2. Monocular: cues that work with one eye (pictorial & motion)
3. Binocular: cues that depend on two eyes (binocular disparity)

Question 2

pictorial cues: occlusion

Answer 2

occurs when one object hides or partially hides another from view → partially hidden object is seen as being farther away

Does not provide information about an object’s absolute distance; it only indicates relative distance

Question 3

pictorial cues: relative height

Answer 3

objects that are below the horizon and have their bases higher in the field of view are usually seen as being more distant

Question 4

pictorial cues: relative size

Answer 4

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

Depends, to some extent, on a person’s knowledge of physical sizes

Question 4

pictorial cues: perspective convergence

Answer 4

when parallel lines extend out from an observer, they are perceived as converging (becoming closer together) as distance increases

Question 5

pictorial cues: familiar size

Answer 5

used when we judge distance based on our prior knowledge of the sizes of objects

Is most effective when other information about depth is absent

Question 6

pictorial cues: atmospheric perspective

Answer 6

occurs when more distant objects appear less sharp and often have a slight blue tint

Question 7

pictorial cues: texture gradient

Answer 7

elements that are equally spaced in a scene appear to be more closely packed as distance increases

Question 8

pictorial cues: shadows

Answer 8

shadows that are associated with objects can provide information regarding the locations of these objects

Question 9

motion-produced cues: motion parallax

Answer 9

occurs when, as we move, nearby objects appear to glide rapidly past us, but more distant objects appear to move more slowly

the image of the far object travels a much smaller distance across the retina, so it appears to move more slowly as the observer moves

is one of the most important sources of depth info

Question 10

motion-produced cues: deletion & accretion

Answer 10

as an observer moves side-ways, some things become covered, and others become uncovered

Are related to both motion parallax and overlap because they occur when overlapping surfaces appear to move relative to one another

Question 11

binocular disparity

Answer 11

the difference in the images in the left and right eyes

Question 12

corresponding points

Answer 12

the places on each retina that would overlap if one retina could be slid on top of the other

if they dont overlap = non-corresponding points

Question 13

horopter

Answer 13

an imaginary surface that passes through the point of fixation and indicates the location of objects that fall on corresponding points on the two retinas

Question 14

angle of disparity & absolute disparity

Answer 14

Angle of disparity = difference between where the image of an object falls on the eye and the (non)corresponding point

Absolute disparity: provides info about the distances of objects - the amount of absolute disparity indicates how far an object is from the horopter - difference between 2 points (corresponding or not corresponding) on each eye

Question 15

relative disparity

Answer 15

the difference between two objects’ absolute disparities - remains the same no matter where an observer looks

(whereas the absolute disparity changes depending on where observer is looking)

Question 16

stereopsis

Answer 16

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

Question 17

correspondence problem

Answer 17

how does the visual system match the parts of the images in the left and right eyes that correspond to one another?

possible answer: the visual system may match the images on the left and right retinas on the basis of the specific features of the objects

Question 18

random dot experiment

Answer 18

Patterns constructed by first generating 2 identical random-dot patterns on a computer and then shifting a square-shaped section of dots to the side by 1 or more units
* contain no monocular cues to depth = shows that disparity alone can create depth perception

Question 19

accomodation & convergence

Answer 19

Convergence: the inward movement of the eyes that occurs when we look at nearby objects

Accommodation: the change in the shape of the lens that occurs when we focus on objects at various distances

Question 20

size-constancy

Answer 20

our perception of an object’s size remains relatively constant, even when we view an object from different distances, which changes the size of the object’s image on the retina

Question 21

size-distance scaling

Answer 21

a mechanism that takes an object’s distance into account (size constancy is based on this)

Equation: S = K (R x D)
S = object’s perceived size
K = constant
R = size of retinal image
D = perceived distance of object