Exam 3 material Flashcards
1.What is stereopsis? …retinal disparity?
“solid vision” = 3D from having two eyes. why? bc right eye and left eye have disparity
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?
they believed one was for redundancy. revision = two eyes provide sense of depth by shifting perspectives
How does strabismus affect a developing visual system?
it starves the binocular data and kills self
What does eye placement have to do with the sensitivity / acuity tradeoff?
lateral eyes = sensitivity
frontal eyes = acute
When draping a tarp over sensitive equipment, why does military protocol typically order that the supports be of varying lengths?
appear “lumpy” like surroundings so that pic from above can perceive flatness
What are random-dot stereograms, and how did Julesz use them to upset a century’s worth of doctrine?
bunch of dots, used to believe see shapes to give rise to depth. actually depth gives sense of shape
What are the stimulus parameters (gross / slight disparities), mental mechanism (rivalry / fusion) and conscious visual experience for binocular rivalry and stereopsis?
slight disparities produces binocular fusion with single line protruding.
gross disparities produces binocular rivalry.
Do animals with laterally placed eyes experience binocular rivalry?
no, bc animal expects to see grossly different images.
What is the inverse optics (projection) problem, and how is one way that vision tries to solve it?
normal = image 1:1 object size and distance
Inverse = image size 1:infinite to object size and distance.
solve. specificy one
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?
Heuristics = quick and sloppy algorithms = accurate but slow
What assumption underlies atmos- pheric perspective, when is this assump- tion mistaken, and what is the result?
clear = nearby
fuzzy = distance
mistaken in little haze
What is T-junction analysis, how does it work, and what assumption underlies it?
the vertical line doesn’t “disappear” behind horiz. line.
assumption = abruptly ending lines dont end abruptly
For 2 items with the same visual angle, which is larger? (nearer / farther)
with same visual angle the nearer object is smaller (so when see things that we “think” are distant we make look bigger)
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?
arrow towards you (appear smaller)
Y away from you (appear larger)
Can you now explain the moon illusion?
assumption that live in flat planes so when distant must be bigger
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?
use shading and prefer floor interpretation.
What are the components of a delay- and-compare cell?
visual and auditory cortex. R and L eye one with delay response to different motion (big delay- slow/ small delay- fast)
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?
for that particular picture cell wouldn’t respond. depending on the rate we may not be able to see it ( too fast or slow)
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?
it would appear to be moving to the right, with straight line. generally, correct and for us assume
What is the ‘assumption’ underlying a delay-and-compare cell?
that they follow the shortest path
What is the shortest-path heuristic?
that in one dot to other will traverse space between in shortest path
What is the wagon-wheel illusion, and why does it occur?
bc see things that could be mistaken for each other. assume it follows shortest path.
In the wagon-wheel illusion demo, what happened when the spokes were color-coded to enable you to see the real direction of motion?
we assume the color changes (Bc motion fat/fast axons are bigger receptors than color skinny/slow axons)
What is motion coherence, and why would we need to detect motion amid a noisy signal?
bc if prey is hiding behind raving grass the coherence of prey being detected will prove beneficial.
What assumption underlies the principle of common fate?
when some things move coherently those are different pieces of same thing
Why do prey animals ‘freeze’ when they detect a predator?
try to defeat predators sense of motion coherence
What was one early explanation for the motion aftereffect, and why does this explanation not suffice for the display used in class?
eye movements, but motion aftereffect of going in two directions at same time cant be explained by eye movements
.What is the neural site underlying the translational aftereffect? …the spiral aftereffect?
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.
What do these two aftereffects indicate about visual processing of motion?
process simple things first, become more complex in visual proceesssing
What was the third dimension of color that we learned about, and can you guess what the corresponding third dimension of sound represents? (timbre)
(Physics) purity (color) saturation (sound) Timbre
What is the main job of the middle ear?
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)
What does this have to do with spike heels and levers?
amplifies force on the pressure points, levers amplify force like ossicles
When scuba diving, how does someone ‘clear their ears’? Why would someone need to do that, and how does it work?
push air though eustachian pathway. when pressure inside is opposit of outside
Why do sounds get quieter when rid- ing in a fast elevator? …when you have a cold?
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)
Why does your recorded voice sound funny to you but not to other people?
bc there is solid born vibrations and air born vibrations. others only hear air born
What is resonant frequency, and how does the cochlea exploit it for transduc- tion?
when one thing vibrates at perfect frequency to vibrate others, cochlea responds and switches (Hi > lo frequency. extract from natural tones to determine pitch)
You know what a ‘retinotopic’ map is; what do you think is meant by a ‘tonotopic’ map?
everyspot on retina 1:1 between retina and cortex. everypart of cortex has 1:1 for frequency
Cochlear hair cells are roughly analogous to __ in vision.
photoreceptors (recieve signal and turn to electricity)
What happens to a tone when its frequency is doubled?
same, but different octave (A = 220, 440, 880)
Why are most cases of acquired deafness clustered around one or several specific frequencies?
around part of auditory processing most fragile (sensitivity increases fragility )
Why can’t the otolith organs distinguish between tilt and linear acceleration? How do you think your perceptual system does it?
bc physically identical (internal goo pushes back in both situation) distingish by use of vision
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
otolithic organs sensitive to linear acceleration/ and tilt. semicircular canals respond to pitch/ roll/ and yaw
Why would being in your cabin on a boat tend to make you seasick, and why does standing on deck provide some relief?
bc vestibular system detects motion, but visually see motion feel better
From an adaptive perspective, why does vertigo tend to induce nausea and vomiting?
because vison and vestibular get decoupled when poisoned, when viscosity of blood and goo is different puke to even it out
Did you ever think that the (outer) ear looks funny? Why does it have such a weird shape?
give sense of sound localization (altitude esp.)
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?
make difference as big as possible (mononeural neuron is stimulated as far apart as possible and bineural neauron can detect dif between two)
A stereo’s two speakers play (slightly) different things, but we don’t notice; why don’t we?
bc percieved to be coming from different areas
Do you see a similarity to visual delay and compare cells?
yes,
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…
dificit in localization
A ‘friend’ once shot a rifle over my head without warning. I now have a defi- cit in __ because …
dificit in frequency and pitch detection
When your physician washes out your ear, you’ll have a temporary deficit in __ because…
deficit in convection current
Ultrasound is reputed to be a safe method for ‘visualizing’ a developing fetus. Should we concern ourselves with the baby’s ears?
ok bc fetus is probably deaf to frequency anyway
