Module 4.2 - The Visual System

Question 1

light travels in waves that vary in terms of 2 different properties. what are these 2 properties?

Answer 1

length and amplitude

Question 2

true or false: different species see different wavelength

Answer 2

true

Question 3

what are the 3 characteristics of light

Answer 3

wavelength, amplitude, purity

Question 4

in what 3 ways are the characteristics of light experienced by us?

Answer 4

hue, intensity and saturation

Question 5

hue

Answer 5

colour of the spectrum

Question 6

intensity

Answer 6

brightness

Question 7

saturation

Answer 7

colourfullness or density

Question 8

sclera

Answer 8

the white, outer surface of the eye

Question 9

cornea

Answer 9

the clear layer that covers the front portion of the eye and also contributes to the eyes ability to focus

Question 10

pupil

Answer 10

regulates the amount of light that enters by changing its size; it dilates (expands) to allow more light to enter and constricts (shrinks) to allow less light into the eye

Question 11

iris

Answer 11

a round muscle that adjusts the size of the pupil; it also gives the eyes their characteristic colour

Question 12

lens

Answer 12

a clear structure that focuses light onto the back of the eye

Question 13

how does the lens focus light onto the back of the eye?

Answer 13

through the process of accommodation

Question 14

retina

Answer 14

lines the inner surface of the eye and consists of specialized receptors that absorb light and send signals related to the properties of light to the brain

Question 15

true or false: the retina consists of a single layer

Answer 15

FALSE: the retina contains a number of different layers

Question 16

photoreceptors

Answer 16

specialized receptors found at the back of the eye; they send information to biopolar and ganglion cells

Question 17

optic nerve

Answer 17

a dense bundle of fibres that transmit activity from the ganglion cells to the brain

Question 18

optic disc

Answer 18

an area on the retina with no photoreceptors

Question 19

blind spot

Answer 19

area on the retina with no photoreceptors

Question 20

why are we not aware of our blind spot?

Answer 20

because the mind “fills in” the blind spot

Question 21

rods

Answer 21

photoreceptors that occupy peripheral regions of the retina; they are highly sensitive under low light levels

Question 22

what colours are rods most responsive to?

Answer 22

black and grey

Question 23

what is the ratio of rods to ganglion cells?

Answer 23

10:1

Question 24

cones

Answer 24

photoreceptors that are sensitive to the different wavelengths of light that we perceive as colour

Question 25

where are the cones clustered?

Answer 25

around the fovea

Question 26

fovea

Answer 26

the central region of the retina

Question 27

what is the ratio of cones to ganglion cells

Answer 27

1:1

Question 28

dark adaptation

Answer 28

the process by which the rods and cones become increasingly sensitive to light under low levels of illumination

Question 29

trichromatic theory/young Helmholtz theory

Answer 29

colour ion is determined by 3 cone types that are sensitive to short (blue), medium (green) and long (red) wavelengths of light

Question 30

what 3 colours are all other colours derived from?

Answer 30

red green and blue

Question 31

opponent-process theory

Answer 31

a competing theory of colour vision, which assume that the visual system treat pairs of colours as opposing or antagonistic

Question 32

opponent-process theory is consistent with _________

Answer 32

ganglion cells

Question 33

colour blindness

Answer 33

total inability to distinguish colours

Question 34

about ___% of all people are partly colour blind

Answer 34

4%

Question 35

colour blindness is often caused by what?

Answer 35

when one type of cones contains the wrong proteins (e.g., "red ones" incorrectly contain the protein found in "green ones")

Question 36

near-sightedness/myopia

Answer 36

when the eyeball is slightly elongated, causing the image that the cornea and lens focus on to fall short of the retina

Question 37

farsightedness/hyperopia

Answer 37

when the length of the eye is shorter than normal, causing the image to be focused behind the retina

Question 38

feature detection cells

Answer 38

cells that selectively respond to simple and specific aspects of a stimulus, such as angles and edges

Question 39

what are the 2 streams of vision

Answer 39

dorsal stream and ventral stream

Question 40

dorsal stream

Answer 40

parietal lobe. visually guided movement. Patient DF

Question 41

ventral stream

Answer 41

temporal lobe. object recognition. involved with recognizing things

Question 42

prosopagnosia

Answer 42

face blindness

Question 43

where does someone with prospagnosia have damage?

Answer 43

have damage to the right fusiform gyrus

Question 44

perceptual constancy

Answer 44

the ability to perceive objects as having constant shape, size and colour despite changes in perspective

Question 45

shape constancy

Answer 45

we see objects as having a constant shape even though the shape of the retinal image produced by an object changes when our point of view changes

Question 46

location constancy

Answer 46

we perceive stationary objects as remaining in the same place even though the retinal image moves about as we move our eyes, heads, and bodies

Question 47

size constancy

Answer 47

we see an object as having constant size even when its retinal image becomes smaller or larger (e.g., an approaching car is not actually growing)

Question 48

brightness constancy

Answer 48

we see objects as having a relatively constant brightness even though the amount of light they reflect changes as the overall level of illumination changes

Question 49

colour constancy

Answer 49

we see an object as maintaining its hue despite the fact that the wavelength of light reaching our eyes from the object may change as the illumination changes

Question 50

binocular depth cues

Answer 50

distance cues that are based on the differing perspectives of both eyes

Question 51

convergence

Answer 51

when the eye muscles contract so that both eyes focus on a single object; it typically occurs for objects that are relatively close to you

Question 52

retinal disparity/binocular disparity

Answer 52

the difference in relative position of an object as seen by both eyes, which provides information to the brain about depth

Question 53

monocular depth cues

Answer 53

visual cues to depth or distance that can be used by one eye alone

Question 54

texture gradients

Answer 54

objects that are coarse and distinct at close range become fine and grainy at greater distances

Question 55

light and shadow

Answer 55

the shadow cast by an object allows us to detect both the size of the object and the relative locations of objects. in addition, closer objects reflect more light than far-away objects

Question 56

motion parallax

Answer 56

when an observer is moving, objects appear to move at different speed and in different directions

Question 57

relative size

Answer 57

if 2 objects in an image are known to be of the same actual size, the larger of the 2 must be closer

Question 58

heigh in plane

Answer 58

objects that are higher in our visual field are perceived as farther away than objects low in our visual field

Question 59

linear perspective

Answer 59

parallel lines stretching to the horizon appear to move closer together as they travel farther away

Question 60

interposition

Answer 60

nearby objects block our view of far-off objects, such as the umbrellas blocking the view of buildings behind them