M2 Lecture 9: Feb 12

Question 1

Perception involves what

Answer 1

figuring out which interpretation of the reality is the most likely

Question 2

what is The pandemonium model of perception

Answer 2

demons represent neurons, and each level is like a brain area.

Committees must integrate conflicting opinions and reach a consensus.

Question 3

what are The Four steps of sensation and perception

Answer 3

physical stimulus–> 1. transduction –> 2. transmission –> 3. perception

Question 4

what is modulation

Answer 4

Cognitive factors, like expectations, attention, etc. will influence how sensations are perceived.

e. g. Top-down vs bottom-up processing
e. g. Bayesian prediction process

Question 5

what are the Committee rules in the pandemonium model

Answer 5

1. Put together what goes together (ex.: Gestalt grouping rules)
2. Avoid accidents (ex.: accidental viewpoint)
3. Honour physics (ex.: occlusion)
   4, Reach consensus (ex.: ambiguous figures)
4. Separate what should be separated (ex.: figure vs ground)
   what i

Question 6

what is Accidental viewpoint

Answer 6

A viewing position that produces some regularity in the visual image that is not present in the world.

(like the 3d paintings on roads that look like such from a certain angle but completely warped from other angles)

Question 7

what is Occlusion

Answer 7

solid objects block light

Question 8

what is Figure-ground assignment

Answer 8

The process of determining that some regions of an image belong to a foreground object (figure) and other regions are part of the background (ground).

Question 9

what are the 5 main Gestalt figure-ground assignment principles

Answer 9

surroundedness
size
symmetry
parallelism
Extremal edges

Question 10

what is Surroundedness:

Answer 10

The surrounding region is likely to be ground.

Question 11

what is Size:

Answer 11

The smaller region is likely to be figure.

Question 12

what is Symmetry:

Answer 12

A symmetrical region tends to be seen as figure.

Question 13

what is Parallelism:

Answer 13

Regions with parallel contours tend to be seen as figure.

Question 14

what is Extremal edges:

Answer 14

If edges of an object are shaded such that they seem to recede in the distance, they tend to be seen as figure.

Question 15

what is Structuralism

Answer 15

Dots make lines -> lines make corners -> corners make shapes -> shapes are connected one to another and make objects.

Question 16

what is the formula for perception

Answer 16

structuralism + committee rules = object perceived

Question 17

what is the Face inversion effect

Answer 17

We are better at recognizing faces that are upright.

Logically, it seems that object recognition should follow figure-ground assignement, but then it shouldn’t matter if the face is up or down….

Question 18

Object recognition also helps with what

Answer 18

figure-ground assignement.

Question 19

is perception just a feed forward process

Answer 19

It cannot all be a feed-forward process, there has to be reciprocal communication between object recognition and figure-ground assignement.

Question 20

what is the Global superiority effect

Answer 20

The properties of the whole object take precedence over the properties of parts of the object

(aka you see the ‘H’ that the small ‘s’s’ make instead of just the small ‘s’s’

Question 21

HOW DO WE RECOGNIZE OBJECTS ?

Answer 21

2 attempted ways to tackle it:
Naïve template theory
Structural description

Question 22

what is Naïve template theory:

Answer 22

The proposal that the visual system recognizes objects by matching the neural representation of the image with a stored representation of the same “shape” in the brain

Question 23

do Naïve template theory work

Answer 23

Naive template theories don’t work

Question 24

what is Structural description

Answer 24

maybe what we recognize is a particular organisation of simpler features?

Question 25

does the Structural description work

Answer 25

Biederman (1987) proposed that any object could be made of a finite set of simpler geons (“geometric ions”). so yes!

Question 26

are Geons and relationships between geons (ex. « geon A is on top of geon B ») are viewpoint invariant

Answer 26

yes

Question 27

what is viewpoint invariant.

Answer 27

Minor changes in shape won’t alter the structural description. (you can recognize a coffee mug as such even If upside-down)

Question 28

even if the structural description is mostly viewpoint invariant, are there still issues

Answer 28

yes-- people still take a much longer time identifying an object the more it has been rotated

Question 29

what are the Three steps to color perception

Answer 29

1. Detection: Wavelengths of light must be detected in the first place. 2. Discrimination: We must be able to tell the difference between one wavelength (or mixture of wavelengths) and another. 3. Appearance: We want to assign perceived colors to lights and surfaces in the world and have those perceived colors be stable over time, regardless of different lighting conditions.

Question 30

what are the Three types of cone photoreceptors

Answer 30

S-cones M-cones L-cones .

Question 31

what do S-cones detect

Answer 31

short wavelengths.

Question 32

what do M-cones detect

Answer 32

medium wavelengths.

Question 33

what do L-cones detect

Answer 33

long wavelengths

Question 34

why are S M and L cones not referred to as blue/green/red

Answer 34

More accurate to refer to them as “short,” “medium,” and “long” rather than “blue,” “green,” and “red,” since they each respond to a variety of wavelengths The L-cone’s peak sensitivity is 565 nm, which corresponds to yellow, not red!

Question 35

how common and sensitive are s cones

Answer 35

relatively rare, and they are less sensitive than M- and L-cones.

Question 36

what are the 2 types of COLOR DETECTION

Answer 36

Photopic | Scotopic

Question 37

what is Photopic:

Answer 37

Light intensities that are bright enough to stimulate the cone receptors and bright enough to “saturate” the rod receptors to their maximum responses. Sunlight and bright indoor lighting are both photopic lighting conditions.

Question 38

what is Scotopic:

Answer 38

Light intensities that are bright enough to stimulate the rod receptors but too dim to stimulate the cone receptors. Moonlight and extremely dim indoor lighting are both scotopic lighting conditions.

Question 39

why is DISCRIMINATION between colours dificult

Answer 39

A single photoreceptor shows different responses to lights of different wavelengths but the same intensity eg. Lights of 450 and 625 nm each elicit the same response from this particular photoreceptor. If you decrease the intensity of the light, lights of 490 and 600 nm will also elicit the same response.

Question 40

what is The principle of univariance

Answer 40

An infinite set of different wavelength x intensity combinations can elicit exactly the same response from a single type of photoreceptor. Therefore, one type of photoreceptor cannot make color discriminations based on wavelength.

Question 41

for every wavelength, there is a particular combination of activity across the three type of cones that remains_____ across different intensities

Answer 41

constant

Question 42

imagine that you don’t have one type of cones (say M-cones), what happens

Answer 42

every frequency above S-cone limit is only encoded by L-cones and can therefore produce the same response for different wavelength/intensity combination. -> However, colors to the left will be preserved.

Question 43

how common is colour blindness

Answer 43

About 8% of male population and 0.5% of female population has some form of color vision deficiency: “color blindness.”

Question 44

what is Color-anomalous

Answer 44

A term for what is usually called “color blindness.” Most “color-blind” individuals can still make discriminations based on wavelength. Those discriminations are just different from the norm

Question 45

what are the types of colourblindness

Answer 45

Deuteranope:. Protanope: Tritanope: Cone monochromat:

Question 46

what is Deuteranope

Answer 46

Due to absence of M-cones

Question 47

what is Protanope

Answer 47

Due to absence of L-cones.

Question 48

what is Tritanope

Answer 48

Due to absence of S-cones.

Question 49

what is Cone monochromat

Answer 49

Has only one cone type; truly color-blind.

Question 50

what is Trichromacy

Answer 50

The theory that the color of any light is defined in our visual system by the relationships of three numbers, the outputs of three receptor types now known to be the three cones. Thomas Young (1773–1829) and Hermann von Helmholtz (1821–1894) independently discovered the trichromatic nature of color perception using a color-matching technique developed by James Maxwell (1831–1879). Three colors were required to match any other color.Two were sometimes insufficient.

Question 51

do we see “pure” wavelengths

Answer 51

Generally, we don’t see “pure” wavelengths, but rather mixtures of wavelengths.

Question 52

When mixing two “pure” wavelengths (say green and red), what happens

Answer 52

the combination of M- and L- cone activity is identical to the combination resulting from a “pure” wavelength in the yellow frequency. We can’t distinguish the two – they will all look yellow

Question 53

what are Metamers

Answer 53

Different mixtures of wavelengths that look identical; more generally, any pair of stimuli that are perceived as identical in spite of physical differences.

Question 54

what is Additive color mixing

Answer 54

: A mixture of lights If light A and light B are both reflected from a surface to the eye, in the perception of color, the effects of those two lights add together.

Question 55

in additive colour mixing, Blue and yellow make what

Answer 55

white

Question 56

what is Subtractive color mixing

Answer 56

A mixture of pigments If pigment A and B mix, some of the light shining on the surface will be subtracted by A and some by B. Only the remainder contributes to the perception of color

Question 57

in subtractive color mixing, blue and yellow make what

Answer 57

green

Question 58

In theory: Since there is no overlap between red and blue paint, when you combine the two all wavelengths are filtered out….the mixture is what

Answer 58

black

Question 59

red paint is really what

Answer 59

white paint + drops of « pure » red

Question 60

blue paint is really what

Answer 60

white paint + drops of « pure » blue

Question 61

1. Red pain is white paint + drops of « pure » red 1. Blue pain is white paint + drops of « pure » blue - > note: « pure » red or blue is very dark 3. When you combine the two, everything is darker overall, but there are still two peaks in red and in blue. 4. thus, the reflected light is what

Answer 61

both blue and red

Question 62

what are nonspectral hues

Answer 62

hues that can arise only from mixtures of wavelengths, i.e. there is no « purple » in the spectrum, it has to come from a particular combination of activity across S, M and L cones.