Lecture 6

Question 1

Depth perception

Answer 1

perception of distance

Question 2

What is so important about depth perception?

Answer 2

there are no cells in the visual system that tell us whether something is far or near us.
distance needs to be inferred from available information in the retina

Question 3

binocular cues

Answer 3

visual cues that depend on both eyes

Question 4

monocular cues

Answer 4

visual cues to distance that are just as effective with one eye as with both

Question 5

Retinal disparity

Answer 5

the difference in the apparent position of an object as seen by the left and right retinas
images are very different earn they are further away - bigger disparity

Question 6

the ability to see depth is a…

Answer 6

learning process that is learnt through interacting with the world

Question 7

convergence

Answer 7

the degree to which the eyes turn in to focus on close objects
the more the muscles contract, then the closer something is to us

Question 8

linear perspective

Answer 8

parallel lines appear to come together in the distance

Question 9

texture gradient

Answer 9

a packed together appearance of objects are further away and have finer texture

Question 10

clarity or bluishness

Answer 10

further away = more blue and less clear
due to light refraction, lights travelled much further

Question 11

object size

Answer 11

close together objects produce larger images
only works for objects of familiar size

Question 12

relative height

Answer 12

below the horizon - further away objects has higher bases
above the horizon - closer objects have higher bases

Question 13

occlusion

Answer 13

objects partially hidden are seen as further away

Question 14

shadows and shading

Answer 14

bigger shadows, bigger distance from the ground

Question 15

accommodation

Answer 15

the lens of the eye changes shape to focus on near objects, our brain detects these changes and infers the distance
flat lens - far object
round lens - near object

Question 16

motion parallax

Answer 16

the difference in speed of movement of images across the retina as you travel
near objects more rapidly across the retina compared to those that are far away

Question 17

size constancy

Answer 17

heuristic - the ability to perceive depth correctly helps us achieve size constancy
even though the retinal projection becomes smaller when the item moves away, we correctly perceive the items correct physical size

Question 18

misjudging distance

Answer 18

when we are misled by the cues that usually help is achieve constancy in size and shape, we experience an optical illusion - a misinterpretation of a visual stimulus

Question 19

misjudging distance leads to misjudging size

Answer 19

we may overestimate distance and therefore overestimate the objects size and can lead to us making incorrect judgments

Question 20

moon illusion

Answer 20

low in the sky, the moon appears bigger than when its higher
yet when you take a picture, they look the exact same

Question 21

what can we learn from optical illusions

Answer 21

perception is a constructive process and involves inferences
the brain computes what light is striking the retina but also learns what objects are present and what they are doing

Question 22

perception is a constructive process and involves inferences

Answer 22

we impose order on patterns
we see 3 dimensions in 2 dimensional drawings
we see optical illusions, as a result of misinterpreted image cues

Question 23

motion perception

Answer 23

to be able to see we need to see changes in the visual signals

Question 24

what is motion perception good for?

Answer 24

helps us with survival - animals freeze in presence of predators (think! DEER)
allows us to interact with the environment
allows us to percieve the results of our actions

Question 25

where is motion in the visual system?

Answer 25

Rods
medial temporal (MT) lobe
in V1, most cells are sensitive to motion and send this information to the MT lobe
MT lobe uses this information to detect motion

Question 26

Motion blindness

Answer 26

damage to the area MT causes the inability to perceive motion
things appear as static images - objects jump in front go you without having moved

Question 27

objects don’t have to be moving for us to perceive motion

Answer 27

motion after effects - adapting to a moving direction causes is to see motion on a static display
motion on the retina is not needed for motion perception

Question 28

corollary discharge theory

Answer 28

retinal slips - an image slips across the retina. either because the object moved or the eyes moves
these retinal slips could be combined with an internal sense of our eyes movements to improve our perception of motion

Question 29

misinterpreting motion

Answer 29

car next to you is moving, you think its your car so you slam the breaks on

Question 30

biological motion

Answer 30

motion produced by humans and animals
can convey gender, activity, intention and mood
studied by using point light walkers

Question 31

brain areas involved in biological motion

Answer 31

activates neurones in are STS - superior temporal sulcus and the FFA - fusiform face area
people with motion blindness can still perceive biological motion

Question 32

biological motion perception may be related to social behaviour

Answer 32

area STS is connected to the orbito-frontal cortex and amygdala - necessary for recognition of social, biological events such as the recognition of emotional expression and personal intenion

Question 33

evidence for the idea biological motion perception may be related to social behaviour

Answer 33

impaired biological perception in individuals with autism
above average biological motion perception in Williams syndrome, a disorder associated with highly social behaviour

Question 34

perception always involves inferences

Answer 34

influenced by experience and context
constancies - retinal images change but our perception remains the same
context effects - retinal image is the same but our perception changes

Question 35

perception is a constructive process

Answer 35

we can see the world as a coherent 3D place despite
- the physiology of the visual system
- the complexities of the distal world

Question 36

2 visual pathways

Answer 36

1 helps us to interact with the world, we are unaware of it but every movement we make is fed by information from this pathway
the other pathway helps us recognise what things are

we don’t have to know what something is before we move to deal with it. e.g you hand can ignore what you think your eyes are actually seeing