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Sensation and Perception > Final > Flashcards

Final Flashcards

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1
Q

Overt attention

A

Directing the eyes and attention to a stimulus

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2
Q

Covert attention

A

Directing attention to a stimulus, while the eyes are fixated elsewhere

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3
Q

selective attention

A

selecting one stimulus to attend to out of many

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4
Q

Attention is like a

A

spotlight; zoom lens

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5
Q

Why attention?

A

Limited capacity in information processing - only so much can be processed at the same time

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6
Q

attentional “bottleneck”

A

individuals have a limited amount of attentional resources that they can use at one time.

Therefore, information and stimuli are ‘filtered’ somehow so that only the most salient and important information is perceived - a subset is selected for further processing

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7
Q

visual search

A

a type of perceptual task requiring attention that typically involves an active scan of the visual environment for a particular object or feature (the target) among other objects or features (the distractors)

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8
Q

response time

A

the time that elapses between a person being presented with a stimulus and the person initiating a motor response to the stimulus

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9
Q

parallel search

A

A search in which multiple stimuli are processed at the same time.

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10
Q

binding problem

A

The challenge of tying different attributes of visual stimuli (e.g., color, orientation, motion), which are handled by different brain circuits, to the appropriate object so that we perceive a unified object (e.g., red, vertical, moving right).

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11
Q

change blindness

A

The failure to notice a change between two scenes. If the gist, or meaning, of the scene is not altered, quite large changes can pass unnoticed.

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12
Q

feature search

A

feature computed over the entire image in parallel; does not require attention

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13
Q

serial search

A

Each item needs to be scanned, RT increases with # of distractors, sequential, self-terminating search

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14
Q

Motion parallax

A

Images of objects have different velocities on the retina depending on their depths

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15
Q

Iso-luminant

A

same luminance, different colors

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16
Q

White light is not “pure” but a

A

composite

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17
Q

Complementary colors

A

Don’t need all wavelengths to obtain white light
Just two can be sufficient
Blue + Yellow = White
Red + Green = White

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18
Q

The yellow paint/filter absorbs

A

short wavelengths

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19
Q

the blue paint/filter absorbs

A

long wavelengths

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20
Q

Trichromacy =

A

retina

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21
Q

Opponecy =

A

Lgn

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22
Q

The “red-green” channel

A

Take the difference between L and M cone responses

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23
Q

The “blue-yellow” channel

A

Take the difference between the (L+M) response and the S response

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24
Q

two possible mechanisms for color constancy

A

Discounting the illuminant
If the entire scene is purplish, it tells you that the illuminant itself is purplish, and our brain suggests we should try to discount the purple we see in the apple
The brain tries to undo the effect of the illuminant

Color contrast
To compare the color of the apple with surrounding regions
If there’s a lot of blue around a patch, the percept is biased away from blue

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25
Horopter
all points at the same perceived depth as fixation
26
Motion parallax
Objects near fixation move slowly across the retina Objects far from fixation move quickly Fixation point has no speed on the retina
27
Geons
Defined by three properties: Shape of cross section Size of cross section Axis: straight or curved
28
Why geons?
Recognizable from almost any viewpoint (cylinder, wedge, soap, noodle)
29
Conjunction search
Real life searches not defined by a single feature | Example: find red peppers in photo of produce section
30
Object-based attention
If you have to disengage your attention from one object and attending to a different one, that takes more effort than attending to one for longer
31
Change blindness
Importance of intervening blank screen - grey blank in between photos blocks the brain from seeing the changes as apparent motion
32
Gist
: quick summary
33
Spatial layout
: layout of objects in 3-d space
34
motion agnosia
Had difficulty pouring water because it looks frozen - no sense of motion Could not see facial movements, mouth of a speaker
35
Motion helps to
Draw attention - especially important because we have small fovea Segment objects from background Relative depth (motion parallax) 3d shape object recognition in impoverished displays
36
Based on point-light motion, | observers can tell:
– sex of walker / dancer – action / kind of dance – identity of a friend – kind of animal
37
motion has two components:
* Direction | * Speed ( = distance / time)
38
Recall: complex cells in v1 are
direction selective
39
Reichardt model
Retinal surface, time delay, directionally-selective cell T1: light at position a (signal delayed for delta t) T2: light at position b (no delay) Cells only fire when it receive inputs from both simultaneously
40
Greater separation between and b in a reichardt detectors,
responds to faster motion
41
Different cells are selective for
different directions of motion different speeds
42
decrease delta t
responds to faster motion
43
threshold for seeing coherent motion
~3% correlated motion
44
with damage to mt, adults need >___% correlated motion to see coherent motion
30
45
monkeys' responses can be predicted by
seeing which mt neurons are responding
46
monkey's responses can be modified by
electrically stimulating specific MT neurons
47
When we adapt to downward motion
neurons selective for downward motion get fatigued - subsequently, a stationary object will appear to move in the upward direction
48
motion after-effect
After adaption, "downward" neurons respond more weakly than "upward" neurons
49
MAE also occurs with
radial motion (i.e, expansion or contraction)
50
motion informs us about
heading direction whether we are on a collision course with an object how soon a "collision' is likely to occur
51
Optic flow
flow patterns created on the retinas by the relative motions of objects
52
backward motion
inward flow (contraction)
53
forward motion
outward flow (expansion)
54
v1 cells have _____ RFs, hence motion is _________
small, ambiguous (aperture problem)
55
V1 cells cannot determine
object motion
56
local motion signals must be integrated to perceive unambiguous motion, this happens in
area MT
57
Area MT
All cells in MT exhibit directional selectivity Much larger RFs than v1 cells An MT cell receives inputs from many V1 cells
58
what is sound?
A vibrating surface generates compressions and rarefactions in the medium (e.g. air)
59
compression
increase in air pressure
60
rarefaction
decrease in air pressure
61
acoustic energy
waves of compression and rarefaction through the medium
62
sound
perceptual experience based on acoustic energy
63
Acoustic waves need
a medium to travel in - can't hear through a vacuum
64
Speed (sound) depends on
density of the medium - faster in liquid than air, even faster in solids
65
amplitude
maximum deviation from baseline pressure - amplitude determines loudness
66
sound intensity is measured in
decibels
67
decibel is a ___ scale
log - adding to the db value, amplitude get multiplied
68
Frequency determines
the pitch of a sound
69
Frequency is measured in
cycles per second (hertz, hz)
70
wavelength
separation from one wave peak to the next
71
normal human range of hearing
50 hz - 20,000 hz
72
wavelength =
1 / frequency
73
sinusoidal acoustic waves are known as
pure tones
74
Fourier's theorem
Any complex wave can be created by adding sine waves
75
vision (fourier's theorem)
any image can be created by adding sine gratings
76
audition (fourier's theorem)
any complex sound can be created by adding pure tones
77
the lowest-frequency component is known as its
fundamental
78
pinna
shell-like flap of the outer ear - gives sound a unique signature, helps in localizing sounds
79
eardrum
thin, oval membrane vibrates in response to the acoustic waves passes vibrations to the middle ear
80
ossicles
"tiny bones" Malleus, Incus, Stapes - passes the vibration from the eardrum to the inner ear and amplifies the vibrations from the eardrum
81
Amplification is needed because
the inner ear (cochlea) is filled with fluid
82
cochlea
3 fluid-filled canals the vibrations from the Stapes set the fluid in motion Generates a wave motion in the basilar membrane converted to nerve impulses in the Organ of corti
83
Organ of corti has ~_____ hair cells per ear
20,000, 1/4 inner HCs (1 row), 3/4 outer HCs (3-4 rows)
84
cilia
bristle-like structures at the top of hair cells
85
___% of nerve fibers originate from _____ hair cells
95, inner
86
transduction takes place mostly in
inner hair cells
87
Outer hair cells _______ the motion of the basilar membrane
amplify - make contact with tectorial membrane contract/expand - motor-like action
88
Temporal theory
Entire basilar membrane vibrates with the same frequency as the sound (like a microphone diaphragm) Sound frequency 500 hz BM vibrates at 500hz nerve fibers fire 500 hz
89
Problems with the temporal theory
Entire BM cannot vibrate uniformly - narrower/stiffer at base; wider/flexible at apex Neurons cannot fire > 1000 hz; but we can hear frequencies up to ~20,000hz
90
The place theory
Bekesy's traveling wave Vibration at oval window set fluid in motion generates a traveling wave along bm gradually increases in amplitude, attains maximum value; then dies down
91
traveling wave theory
locus of maximal amplitude depends on sound frequency High-frequency: near base Low-frequency: near apex Different groups of hair cells are activated along BM Nerve signals initiated in different fibers along cochlea
92
tonotopic organization
precise mapping between sound frequency and location frequency encoded by location along cochlea where nerve fibers are active

Sensation and Perception (4 decks)

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