Perception I Flashcards

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1
Q

What are the 5 steps of visual processing?
(recap)

A

Photoreceptors
-> light is transduced into neural signals
-> photorecptors in retina
(rods vs cones,
fovea vs periphery,
scotopic vs photopic vision)

Ganglion Cells
-> summarize information from several photoreceptors
(Donut-shaped receptive fields as ganglion cells
centre vs surround,
on-centre vs off-centre ganglion cells)

LGN cells
-> Ganglion Cells send information to LGN cells
(same Donut-receptive fields as ganglion cells
feedback from higher-level areas)

Striate Cortex
-> cells summarize information from LGN cells
(Building “line detectors” from donuts
orientation tuning
simple vs complex cells
end stopped cells)

Higher-level brain areas
-> responding to increasingly complex and specific stimuli
(faces,
places,
body parts,
hands)

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2
Q

What are the different cell types in low-level vision?
(recap)

A

Retina
-> Ganglion Cell
-> Donut-shape
-> Dot of light surrounded by darkness or vise versa

LGN
-> LGN Cell
-> Donut-shape
-> Dot of light surrounded by darkness or vise versa

Striate Cortex
-> simple cell
-> elongated, clearly divided
into excitatory / inhibitory
-> Orientation tuning possible
-> stimulus exactly on ON7OFF region
=> edge detector
-> one, one inhibitory are
froming a clear edge
-> Edge between light and dark
=> stripe detector
-> excitatory stripe between two
inhibitory areas (or vice versa)
-> stripe of light between dark (or vice versa)

-> Complex cell
-> elongated, not clearly divided
inte excitatory / inhibitory
-> Orientation tuning possible
-> stimulus anywhere within receptive field

=> end stopped cell
-> stimulus of specific length

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3
Q

What are the different vision levels?
(recap)

A

Low-level vision
-> extracting basic image features
(edges, lines, patterns from the image)
-> simple yet abstract stimulus properties
-> in striate cortex

Mid-level vision
-> Grouping low-level features together into objects
-> identifying boundaries and surfaces in an image

High-level vision
-> identifying complex stimuli
(such as faces, places, body parts)
-> inferior temporal cortex
(FFA, PPA, EBA)

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4
Q

What is the key function of mid-level vision?
(mid-level vision)

A

Keyfunction of mid-level vision
-> figure ground assignment
(black object, white background or vice versa)
(not fully closed figure on same color background)
=> boundary detection

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5
Q

What attributes helps us differentiate between figure and background?
(mid-level vision)

A

Surroundedness
-> background usually surrounds figure

Size
-> figure is usually smaller than background

Symmetry
-> figure is more likely to be symmetrical

Parallelism
-> parallel contours more likely to be figure

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6
Q

What is bottom-up und top-down processing?
(mid-level vision)

A

Perception is always an interplay of

Bottom-up processing
-> information about the environment as
represented by the senses
(Sound, Color, Features, Location, Movement)

Top-down processing
-> Information about the environment that
an individual brings
(Knowledge, Expectation, Experience, Memory, Culture)

=> Interpretation trough Top-down and Bottom-up
processing

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7
Q

What is the dynamic cycle of perception?
(mid-level vision)

A

Stimulus
1. Environmental stimulus
2. Attended stimulus
3. stimulus on the receptors

Electricity
4. Transduction
5. Transmission
6. Processing

Experience and action
7. Perception
8. Recognition
9. Action

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8
Q

What can perception be defined as?
(mid-level vision)

A

Perception
-> process of recognizing, organizing, interpreting
from senses
-> Not an exact copy of the world
-> based on our past experience and espectations

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9
Q

What 2 approaches are there to understanding perception?
(mid-level vision)

A

Direct perception theories
-> focus on bottom-up processing
-> perception comes from stimuli in the environment
-> parts are identified and put together
then recognition occurs

constructive perception theories
-> focus on top-down processing
-> people actively construct perceptions using
information based on expectations

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10
Q

What are direct perception theories?
(mid-level vision)

A

Biederman (1987)
Recognition by components theory (RBC)
= elemental features: “geons” 3D shape
-> Objects are recognized by perceiving elementary
features
-> 36 different geons identified
-> idea that neurons along neral hierarchy process
increasingly complex stimuli

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11
Q

What are constructive perception theories?
(mid-level vision)

A

focus on top-down processing
-> basing one perception on another
-> interferences based on context
-> guessing from experiences
(making sense of ambiguous stimuli)

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12
Q

What is the Ebbinghaus size illusion?
(mid-level vision)

A

Illusion where on perception is based on another

example
size of an orange circle perceived
-> smaller when surrounded by bigger sized black circles
-> bigger when surrounded by smaller sized black circles

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13
Q

What is Helmholtz’ theory of unconsious inference
(Gestalt principles)

A

When image on the retina is ambiguous
-> perceptual system decides

Unconscious inference
->likelyhood principle
(most likely interpretation is favoured)

-> based on unconscious assumptions, inferences about
the environment

=> process is rapid, feels almost automatic

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14
Q

What is the Gestalt psychology?
(Gestalt principles)

A

Wertheimer, Köhler, Koffka
Gestalt psychology
-> the perceptual whole is more than the sum of its
sensory parts
-> the mind groups patterns according to rules of
perceptual organization
(Gestalt principles)

Gestalt psychologists
-> see gestalt principles as “intrinsic laws”
(built into the system)
-> effect of perceptual princles should be stronger
than effect of experience with the world
-> only minor role of experience

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15
Q

What are the gestalt principles?
(gestalt principles)

A

Good continuation
-> points connecting to form straight or smoothly curving
lines
-> perceived as belonging together
-> lines are seen in a way to follow the smoothes path

Prägnanz
-> principle of simplicity or good figure
-> patterns are seen in the simplest way possible

Similarity
-> similar things appear to be grouped together
-> color, size, shape, orientation
determine similarity
-> grouping also as result of enclosure or proximity

Occlusion
-> when an object is partially covered by another, we
perceive it as continuing behind that object

Familiarity
-> Elements are more likely to form groups when groups are familliar or meaningful

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16
Q

What does it mean that Gestalt principles are heuristics?
(gestalt principles)

A

heuristic = rules of thumb
-> provide best-guess solution to a problem
-> fast
-> definite result

17
Q

Why are heuristics useful?
(gestalt principles)

A

functionality
-> quickly derive a useful interpretation of a stimulus
-> unlikely configurations are usually ignored
(even when they are possible)
-> makes everyday perception efficient

practicallity
-> Visual input on our retina is always ambigous
-> we have to settle on one interpretation

18
Q

What are modern psychologists discussing?
(gestalt principles)

A

Modern psychology
-> Experience with the environment as a central component to perception

Physical regularities
-> perceived distance,
-> light-from-above heuristic

Semantic regularities
-> thematic relation
-> co-occurrence of objects

19
Q

What are the principles involved in perceived distance?
(gestalt principles)

A

Occlusion
-> we know that houses behind cars because the cars
cover the houses

Linear perspective
-> we know that parallel lines converge in the distance
-> ponzo illusion
(same length line in front and distance)

Haze or aerial perspective
-> objects that are far away appear “hazy” or “fuzzy”

20
Q

What is perceived size?
(gestalt principles)

A

Perceived size of an object is the result of

Bottom-up processing
-> size of the image on the retina
(visual angle, relative)

Top-down processing
-> perceived distance of the object
-> size of object relative to other objects in the
environment

21
Q

What is object co-occurence?
(gestalt principles)

A

= We rely on scene context and object co-occurence to identify ambigiuous objects

-> semantic regularities

22
Q

What is the Light-from-above heuristic?
(gestalt principles)

A

=We assume that light comes from above
-> therefore interpret shadows as cues towards 3D shape