PSY280 - 7. Depth Flashcards

Question

motion parallax

Answer 1

When an observer moves, objects nearer observer move faster than more distant objects: fence pickets: fast = close farm house: slow = far

Answer 2

image of house moves a shorter distance on retina, so it looks like it’s moving more slowly as observer moves. retina at position 1 + position 2 plot how far object has moved on retina

Answer 3

relative positions change as dog is moving | as moving - some things are being covered - deletion - others revealed - accretion

Answer 4

brain receives kinaesthetic info about eye position How far eyes roll in (close)/out (far) gives info far away, eyes roll out to be parallel eyeballs move inward for something close in both cases - keep same object on same foveal point

Answer 5

limit as to how much info it can give you - arm length or less: most parallel that they’re gonna be

Answer 6

lens changes shape to bring light into focus on retina: •thinner g far •thicker g close brain gets info from eye muscles that control accomodation

Answer 7

knows when lens is thinner + thicker accommodation + convergence coupled useful within reaching distance, but don’t need 2 eyes for these

Answer 8

examining corresponding points on the retinas. overlap retinas - identify corresponding points By fixating the green gummie bear, the image falls on corresponding F points on the retinas F = fixation + fovea

Answer 9

every time you fixate - imaginary arc that passes through fixation: anything on horopter falls on corresponding points on the retina Objects not on horopter fall on non-corresponding points on retinas

Answer 10

further from horopter, greater angle of disparity | anything on the horopter = same distance from where you are fixated

Answer 11

on non corresponding points means they’re not the same distance as you gives you info about how far from horopter, but not whether its front or behind

Answer 12

Objects in front of horopter in crossed disparity In the right eye unfixated object is to the left of fixated object, vice versa when fixating red, blue is in front of horopter

Answer 13

Objects behind of horopter are in uncrossed disparity In the right eye unfixated object is to the right of fixated object, vice versa. how far based on angle of disparity

Answer 14

Retinal disparity sufficient to create the perception of depth 3D glasses - filters means you deliver diff images to each eye giving binocular disparity Wheatstone: invented stereoscope depth perception given by retinal disparity taken advantage of knowledge with 3D images, viewmaster

Answer 15

Free fusion requires you to decouple accommodation and convergence. when converged on close objects lens becomes thicker need to converge eyes + allow lens to become thinner in either case, have to figure out which bit of image in left eye corresponds to which bit is presented in right eye by matching up object identity

Answer 16

developed random dot stereograms, which have retinal disparity without pictorial cues. but produced random dot stereograms which have retinal disparity matching 2 disparate images is how we perceive depth even with no features, disparity is enough of a cue

Answer 17

using retinal disparity, but trick is to look through image | roll eyes out - produce slightly diff images - disparate images

Answer 18

receive inputs from both eyes; receptive field on one retina is slightly adjacent to corresponding point on other retina has to be in V1 - that’s where you start getting input from both eyes

Answer 19

in a, b, c fixation point is the same | when person is fixated at dot, object slightly in front of horopter produces angle of disparity

Answer 20

responds best to stimulus closer to and slightly to the right of fixation: fall on receptive field of red neuron - maximum stimulation in front a little to right

Answer 21

responds best to stimulus further from + slightly to the left of fixation behind of horopter + a little to the left maximum response from blue neuron

Answer 22

animal models stereograms allow you to deliberately control level of disparity in images you are presenting using diff amounts of disparity - find tuning curve each binocular disparity neuron has diff preferential disparity level find optimal disparity

Answer 23

3-5% of ppl are stereo blind - don’t have binocular disparity neurons can’t use binocular depth cues strobismus - V1 don’t learn to integrate info from 2 eyes thought to have sensitive period she learned stereo vision in her 40s never too late to learn stereo vision

Answer 24

depth can give us a clue about size if take up same amount of space in retina - one farther away is bigger pictorial cues tell us that suv at back is farther away

Answer 25

angle subtended by an object on the retina tan (Θ) = size distance VA - irrespective of visual size: takes into account size + distance of viewing

Answer 26

really large object can take up small space if really far small object can take same amount of space but closer after images diff size on screen + paper

Answer 27

farther away an afterimage appears, the larger it will seem size-distance scaling: S = k(R x D) s - perceived physical size dependent on k as a constant

Answer 28

how much space on retina (R) x distance (D) further so it seems large on paper - perceived size is smaller, same space on retina

Answer 29

``` if objects same physical size, but take up different amounts of space on the retina, MUST be at different depths (R) °VA = different (S) size = same (D) depth = ? S=RxD SL = 10°x10=100 SR = 5°x20=100 ```

Answer 30

hand isn’t changing size, but amount of space taking up on retina diff taking up less space on retina, same space, but now larger distance

Answer 31

``` if objects are at diff distances but take up same amount of space on retina, must be diff physical sizes (R) VA = same D depth = diff S size = ? S -R x D SR = 10 x 10 = 100 SB = 10 x 20 = 200 if at diff depths, then they can’t be the same size ```

Answer 32

perception of an object’s size stays relatively constant, even when we view the object from diff distances retinal space is smaller, but distance is increasing, so same size

Answer 33

Subjects matched physical size of the test circle sat in a hallway

Answer 34

each test circle 1 degree of VA, but varied physical size of object closer, object had to be small, far, big object they didn’t match VA, but physical size also considered distance

Answer 35

unless depth cues were removed, subjects matched visual angle 1. all depth cues available 2. remove binocular depth cues 3. look at peep hole - remove motion depth cues 4. one eye, peep hole, curtains in hallway to remove pictorial depth cues don’t need binocular to be good at perceiving depth

Answer 36

can also be achieved based on familiar objects for comparison

Answer 37

centre line is exactly the same length

Answer 38

inside corners are receding, outside corners are jutting out S=RxD seeing outward facing fin as inside corner inside facing fin as outside corner

Answer 39

inward facing fin needs to be about 7% larger for noneuropean, need to be 20% larger for europeans ppl in european civilizations deal with a lot of buildings nomadic pops not really have experience, less likely to engage in this effect can’t explain all of it because noneuropeans aren’t at 0

Answer 40

2 (conflicting) cues to length: •line length •overall length of the figure also works with similar, but slightly diff versions

Answer 41

manipulation of pictorial cues makes it seem as if objects are at different distances S = R x D

Answer 42

manipulation of pictorial cues makes it seem as if 2 people are at the same distance.

Answer 43

moon looks larger when it is near the horizon than when it is overhead. °VA is constant in the same night, and doesn’t vary much over the course of a year

Answer 44

assumptions about the shape of sky makes it seem as if the moon is at different distances flattened bowl effect assume sky overhead closer to us than sky on horizon same R diff D, larger D when on the horizon

Answer 45

sky is huge But the moon is only a small fraction of that… it must be small appears larger when close to large object sky makes moon look smaller