Exam 3 material

Question 1

1.What is stereopsis? …retinal disparity?

Answer 1

“solid vision” = 3D from having two eyes. why? bc right eye and left eye have disparity

Question 2

Through most of human history, what did the prevailing wisdom think was the reason for having two eyes? When did we revise our ideas about the utility of two eyes, and why?

Answer 2

they believed one was for redundancy. revision = two eyes provide sense of depth by shifting perspectives

Question 3

How does strabismus affect a developing visual system?

Answer 3

it starves the binocular data and kills self

Question 4

What does eye placement have to do with the sensitivity / acuity tradeoff?

Answer 4

lateral eyes = sensitivity

frontal eyes = acute

Question 5

When draping a tarp over sensitive equipment, why does military protocol typically order that the supports be of varying lengths?

Answer 5

appear “lumpy” like surroundings so that pic from above can perceive flatness

Question 6

What are random-dot stereograms, and how did Julesz use them to upset a century’s worth of doctrine?

Answer 6

bunch of dots, used to believe see shapes to give rise to depth. actually depth gives sense of shape

Question 7

What are the stimulus parameters (gross / slight disparities), mental mechanism (rivalry / fusion) and conscious visual experience for binocular rivalry and stereopsis?

Answer 7

slight disparities produces binocular fusion with single line protruding.
gross disparities produces binocular rivalry.

Question 8

Do animals with laterally placed eyes experience binocular rivalry?

Answer 8

no, bc animal expects to see grossly different images.

Question 9

What is the inverse optics (projection) problem, and how is one way that vision tries to solve it?

Answer 9

normal = image 1:1 object size and distance
Inverse = image size 1:infinite to object size and distance.
solve. specificy one

Question 10

What are the relative advantages and disadvantages of heuristics and algo- rithms? Which is preferred by your visual system, and what does this tell us about vision?

Answer 10

Heuristics = quick and sloppy
algorithms = accurate but slow

Question 11

What assumption underlies atmos- pheric perspective, when is this assump- tion mistaken, and what is the result?

Answer 11

clear = nearby
fuzzy = distance
mistaken in little haze

Question 12

What is T-junction analysis, how does it work, and what assumption underlies it?

Answer 12

the vertical line doesn’t “disappear” behind horiz. line.

assumption = abruptly ending lines dont end abruptly

Question 13

For 2 items with the same visual angle, which is larger? (nearer / farther)

Answer 13

with same visual angle the nearer object is smaller (so when see things that we “think” are distant we make look bigger)

Question 14

Corners that jut out towards you appear to be __ - terminated lines, whereas corners that recede away from you appear to be __ - terminated lines. What does this have to do with the Muller-Lyer illusion?

Answer 14

arrow towards you (appear smaller)

Y away from you (appear larger)

Question 15

Can you now explain the moon illusion?

Answer 15

assumption that live in flat planes so when distant must be bigger

Question 16

What assumption does the visual system make when trying to decide if the landscape feature in the Arizona desert is a dimple or a pimple? What’s the story with the pieplate? …rolling ball?

Answer 16

use shading and prefer floor interpretation.

Question 17

What are the components of a delay- and-compare cell?

Answer 17

visual and auditory cortex. R and L eye one with delay response to different motion (big delay- slow/ small delay- fast)

Question 18

With the cell that we designed, what would have happened if the fly had been moving to the left?…what would happened if the fly had been moving at a different rate?

Answer 18

for that particular picture cell wouldn’t respond. depending on the rate we may not be able to see it ( too fast or slow)

Question 19

In the cell we designed, what would have happened if the fly had winked into existence in RFA, then winked out of ex- istence just as another fly had winked in- to existence in RFB? What does this have to do with apparent motion?

Answer 19

it would appear to be moving to the right, with straight line. generally, correct and for us assume

Question 20

What is the ‘assumption’ underlying a delay-and-compare cell?

Answer 20

that they follow the shortest path

Question 21

What is the shortest-path heuristic?

Answer 21

that in one dot to other will traverse space between in shortest path

Question 22

What is the wagon-wheel illusion, and why does it occur?

Answer 22

bc see things that could be mistaken for each other. assume it follows shortest path.

Question 23

In the wagon-wheel illusion demo, what happened when the spokes were color-coded to enable you to see the real direction of motion?

Answer 23

we assume the color changes (Bc motion fat/fast axons are bigger receptors than color skinny/slow axons)

Question 24

What is motion coherence, and why would we need to detect motion amid a noisy signal?

Answer 24

bc if prey is hiding behind raving grass the coherence of prey being detected will prove beneficial.

Question 25

What assumption underlies the principle of common fate?

Answer 25

when some things move coherently those are different pieces of same thing

Question 26

Why do prey animals ‘freeze’ when they detect a predator?

Answer 26

try to defeat predators sense of motion coherence

Question 27

What was one early explanation for the motion aftereffect, and why does this explanation not suffice for the display used in class?

Answer 27

eye movements, but motion aftereffect of going in two directions at same time cant be explained by eye movements

Question 28

.What is the neural site underlying the translational aftereffect? …the spiral aftereffect?

Answer 28

translational aftereffect is early V1
spiral is late in MT or V5
interocular transfer for spiral is more robust than for translational bc early vision every cell is monocular, becomes binocular. bc translational aftereffect happen earlier where there are monocular cells.

Question 29

What do these two aftereffects indicate about visual processing of motion?

Answer 29

process simple things first, become more complex in visual proceesssing

Question 30

What was the third dimension of color that we learned about, and can you guess what the corresponding third dimension of sound represents? (timbre)

Answer 30

(Physics) purity (color) saturation (sound) Timbre

Question 31

What is the main job of the middle ear?

Answer 31

air is relatively rarified compared to water, must amplify with osicles and input is greater than output (increases pressure force/surface area > make denominator smaller everything else bigger)

Question 32

What does this have to do with spike heels and levers?

Answer 32

amplifies force on the pressure points, levers amplify force like ossicles

Question 33

When scuba diving, how does someone ‘clear their ears’? Why would someone need to do that, and how does it work?

Answer 33

push air though eustachian pathway. when pressure inside is opposit of outside

Question 34

Why do sounds get quieter when rid- ing in a fast elevator? …when you have a cold?

Answer 34

reduces air pressure on outside of eardrum, wont vibrate as would before. when have cold things also dont vibrate as much (bc tissue is swollen and cant ballance pressure)

Question 35

Why does your recorded voice sound funny to you but not to other people?

Answer 35

bc there is solid born vibrations and air born vibrations. others only hear air born

Question 36

What is resonant frequency, and how does the cochlea exploit it for transduc- tion?

Answer 36

when one thing vibrates at perfect frequency to vibrate others, cochlea responds and switches (Hi > lo frequency. extract from natural tones to determine pitch)

Question 37

You know what a ‘retinotopic’ map is; what do you think is meant by a ‘tonotopic’ map?

Answer 37

everyspot on retina 1:1 between retina and cortex. everypart of cortex has 1:1 for frequency

Question 38

Cochlear hair cells are roughly analogous to __ in vision.

Answer 38

photoreceptors (recieve signal and turn to electricity)

Question 39

What happens to a tone when its frequency is doubled?

Answer 39

same, but different octave (A = 220, 440, 880)

Question 40

Why are most cases of acquired deafness clustered around one or several specific frequencies?

Answer 40

around part of auditory processing most fragile (sensitivity increases fragility )

Question 41

Why can’t the otolith organs distinguish between tilt and linear acceleration? How do you think your perceptual system does it?

Answer 41

bc physically identical (internal goo pushes back in both situation) distingish by use of vision

Question 42

The otolithic organs are sensitive to: …semicircular canals are sensitive to: …Looking upward (or downward) and spinning around tends to stimulate the part of the vestibular system sensitive to:
Pitch / Roll / Yaw / Tilt /
Linear acceleration

Answer 42

otolithic organs sensitive to linear acceleration/ and tilt. semicircular canals respond to pitch/ roll/ and yaw

Question 43

Why would being in your cabin on a boat tend to make you seasick, and why does standing on deck provide some relief?

Answer 43

bc vestibular system detects motion, but visually see motion feel better

Question 44

From an adaptive perspective, why does vertigo tend to induce nausea and vomiting?

Answer 44

because vison and vestibular get decoupled when poisoned, when viscosity of blood and goo is different puke to even it out

Question 45

Did you ever think that the (outer) ear looks funny? Why does it have such a weird shape?

Answer 45

give sense of sound localization (altitude esp.)

Question 46

Why do you think that our ears are as far apart as they can get, on the sides of the head, and not closer together, like on the forehead?

Answer 46

make difference as big as possible (mononeural neuron is stimulated as far apart as possible and bineural neauron can detect dif between two)

Question 47

A stereo’s two speakers play (slightly) different things, but we don’t notice; why don’t we?

Answer 47

bc percieved to be coming from different areas

Question 48

Do you see a similarity to visual delay and compare cells?

Answer 48

yes,

Question 49

Van Gogh was well known to have cut off his pinna. Afterwards, he would have a deficit in (localization / sensitivity to one frequency / his vestibular sense), be- cause…

Answer 49

dificit in localization

Question 50

A ‘friend’ once shot a rifle over my head without warning. I now have a defi- cit in __ because …

Answer 50

dificit in frequency and pitch detection

Question 51

When your physician washes out your ear, you’ll have a temporary deficit in __ because…

Answer 51

deficit in convection current

Question 52

Ultrasound is reputed to be a safe method for ‘visualizing’ a developing fetus. Should we concern ourselves with the baby’s ears?

Answer 52

ok bc fetus is probably deaf to frequency anyway