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Perception and Cognition > perception > Flashcards

perception Flashcards

1
Q

What is contrast and how does it track over the lifespan

A

It declines with age - around or 60s
Differences in luminance over a scene
Can be very debilitating if lost

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2
Q

Where is contrast processed

A

Retina
LGN
Cortex

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3
Q

What is luminance and how is it measures

A

Measure of energy emitted or reflected by a light source

Measured by candelas per sq metre (CD/M2)

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4
Q

What is michelson contrast

A

Maximum luminance - minimum luminance / average luminance

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5
Q

What is a linear receptive field

A

The region of space where changes in luminance influence the activity of a single neutron
It is linear as excitatory and inhibitory are summed
Neurone respond to stimuli they are tuned in for

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6
Q

Why do we get the Hermann grid illusion

A

We see the little grey dots in the intersections as there is a smaller neuronal response
When we focus on the intersection the smudge is not visible- we can resolve details with more accuracy at the centre of our vision

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7
Q

What are v1 simple cells tuned in for

A

Tuned in for orientation

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8
Q

v1 complex cells?

A

2 linear filters are squared and summed

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9
Q

What is the LGN characterised by

A

Gain control mechanisms

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10
Q

What is cortical processing characterised by

A

Nonlinear processsing

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11
Q

Hierarchy of processing

A

Receptors
Neuron transmit info
Thalamus (relay station)
Cortical processing

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12
Q

What is electrophysiology

A

Fine wires are inserted into areas of interest
It had high spatial selectivity
We can measure cells in real time

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13
Q

Ventral pathway?

A

“What”
LGN to temporal lobe
Object processing and fine detaol

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14
Q

Dorsal pathway?

A

“How”
LGN to parietal lobe
Motion and spatial processing

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15
Q

Where is colour coded

A

V4

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16
Q

Where is motion coded

A

V5/MT

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17
Q

What happens if there is damaged to v4

A

Can’t perceive colour

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18
Q

What happens if there is damage to V5/Mt

A

Can’t process motion

Couldn’t cross road

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19
Q

Experimental evidence for maps in the brain?

A

A dye was attached to structures to show where a stimulus is represented in an area of the brain
Monkeys

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20
Q

What are some experimental techniques used when investigating cognitive processes

A 
Psychophysics
Single cell recording (electrophysiology)
fMRI
EEG
Adaptive optics
Optical imaging
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21
Q

What type of data comes from psychophysics and some techniques used?

A

Behavioural data not neural

Method of constant stimuli, method of limits, method of adjustment, staircase procedure

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22
Q

What can the method of constant stimuli tell us / what term is used to describe this

A

It is measuring how well people can discriminate between 2 lines
The threshold for detecting differences in the position of 2 lines was smaller than the width of a photoreceptor
Termed hyperacuity

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23
Q

Why continue to do psychophysics instead of collecting neural data

A

Neural data is expensive and takes time
Linking propositions more complex for neural data
Psychophysics and neuro imaging are complementary

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24
Q

Paradigms for fMRI

A

Block design: neural activity is compared when stimulus is present or absent
Event related: neural activity at a certain time after stimulus is presented. Compared across conditions
Combined: make inferences about substrates of human behaviour

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25
Q

2 cortical surfaces

A

Sulci- dark grey concave

Gyri- light grey convex

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26
Q

Periperternal space?

A

50-100cm in front of you- you can discriminate object in depth really well
Within this zone you are using binocular disparity

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27
Q

What is occlusion

A

We know 2/3 of things don’t exist - it is hiding behind another object

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28
Q

What is size constancy

A

You know how big an object should be

Don’t think someone is shrunk just because they are fair away

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29
Q

What is the Ames room

A

An optical illusion

We used cues from the room and it shows us the kids are two different sizes when they are actually the same size

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30
Q

What is the ponzu illusion

A

We assume the lines are getting smaller as they are further away but they are actually the same size
We misapply size constancy and what we know about depth
Kids in western societies more likely to see this than non western

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31
Q

Occlusion and size constancy are what type of clues

A

Contextual clues - create context about a scene

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32
Q

What are monocular vs binocular cues

A

Monocular- we use one eye

Binocular- Info is combined from both eyes

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33
Q

What type of cue is motion parallel and what does it do

A

It is a monocular cue
Used for depth ordering
Objects move around us as we move
Angle small for distant object, wide for close object

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34
Q

What is binocular disparity

A

The difference between the left and right eye relative to the plane of fixation (heropter)

35
Q

What is crossed / uncrossed disparity

A

Objects prior to our plane of fixation have disparity crossed
Objects beyond our plane of fixation have disparity uncrossed

36
Q

Name 2 sensor intro cues

A

Accomodation and vergence

37
Q

What is accomodation

A

Changing focal length using ciliary muscles to calculate distance of object
Relaxed muscles for things further away
Tightened muscles/ squeezed to focus on something closer to you

38
Q

What happens with accomodation and age

A

As we age our lens becomes less flexible, so we can’t adjust our focal length
Can’t accomodate to objects of different distances

39
Q

If you can’t accommodate your lens you may end up with

A

Long sighted vision (hyperopic eye)

Short sighted vision (myropic eye)

40
Q

What lens would u use to correct for a hyperopic eye

A

Convex

41
Q

What lens would u use to correct for a myopic eye

A

Concave

42
Q

What is convergence

A

Angle of gaze of two eyes
When something is further away eyes move inward, angle of convergence smaller
When something is closer, angle of convergence is larger

43
Q

What is strabismus

A

Misalignment of eyes often caused by different muscle tension
Exotrope- eye moves outward
Esotrope- eye moves inward
Can be fixed with surgery
If not fixed within a critical period can result in damages to contrast sensitivity and binocular depth perception

44
Q

What is stereo good for

A

Fine motor control

Sewing surgery picking berries

45
Q

What is disparity good for

A

Useful for testing stereo vision
VR
Movies
Hugh risk jobs

46
Q

2 limits imposed by vision

A
  1. People use binocular and monocular cues. But VR relies on binocular cues so people with compromised stereo may just see 2 displaced images
  2. We only have high resolution at the place we are looking at
    In natural environments we are always changing our focal planes as we move around but you can’t do that with VR. This causes headaches eye fatigue bc our vision is forced to combine cues that aren’t normal
47
Q

What does Reinhardt model comprise

A

Spatial and temporal filters

48
Q

Why is energy model better than reichardt

A 
It has an extra step which allows quadrature pairs to be squared and summed to calculate motion energy and have responses oriented in time and space
Less fussy than reichardt mode
More specific
More flexible 
Can detect more complex motion
49
Q

Why does the aperture problem happen

A

Completion between local and global features of a scene

The motion is featureless - any pattern looks like any other part

50
Q

How to solve aperture problem

A

Orientation info can disambiguate edges
Changing the orientation of aperture can change its direction of motion
If vertical, lines go up and down
If horizontal lines go left to right or right to left

51
Q

What can form information do

A

Can generate or disambiguate motion

52
Q

How does form information generate perception of motion

A

Glass pattern- dots have no correspondence (no motion)
Within 10-15 frames people detect motion
Thought to happens bc dot pairs simulate motion streaks

53
Q

Biological motion?

A

People see a person walking just bc of light points of joints
Used high level constraints (our idea of what a person should look like) on low level info (dots)

54
Q

How much of visual cortex devoted to visual processing

A

1/3

55
Q

2 components of hand movements?

A

Planning phase

Guidance phase

56
Q

What happens in planning phase

A

Visual info about target and hand plot course of action

Plot action trajectory, velocity movement plan to make movement as accurate as possible

57
Q

What happens in guidance phase

A

You compare your hands location to the target, which you can use to update the movement plan to be more precise
In acceleration stage, movement plan dominanates velocity and trajectory
In deceleration phase, plan is subservient to updating information

58
Q

4 limiting factors on performance

A

Bio mechanical costs
Risk
Visual error
Motor error

59
Q

What are bio mechanical costs

A

Energy expenditure involved when making movements and muscle stress involved

60
Q

Risk

A

Sometimes a cost to making an inaccurate movement

Surgery picking berries

61
Q

Motor error/ Fitts law

A

Speed accuracy tradeoff
Less accurate with fast movements
More accurate with slow movements bc you have time for feedback

62
Q

What does movement depend of

A

Visual quality and associated error

63
Q

2 things to minimise visual error

A

Light is better to see the target

Still targets- but doesn’t happen much in real life

64
Q

What is online control of movement

A

When u alter motor plan based on the discrepancy between predicted and real feedback

65
Q

How many milliseconds to update a slow reach

A

110-150

66
Q

Are movements ballistic

A

No - we can use visual information throughout our reach to update performance to be more accurate

67
Q

How do we know the posterior parietal cortex plays a role in online correction

A

Through TMS experiments (trans cranial magnetic stimulation)
Electric magnetic coil placed on scalp where the target region lies
It disrupts nerve cells in target region
Movements and points are less accurate

68
Q

What is developmental coordination disorder

A

Clumsy kids have trouble with fine motor skills- sport and writing
What causes it unclear
Probs due to deficits in visual and motor mapping
Maybe Dorsal impairment

69
Q

What happens with parietal damage

A

Often caused by stroke
Sometimes can lead to visual neglect
You only attend to one side of the visual field
You are unaware of this tho

70
Q

2 common eye movements ?

A

Saccades and smooth pursuit

71
Q

Reaches are planned in …. coordinates??

A

Eye centred not arm centred

72
Q

What are saccades

A

Eye movement characterised by rapid acceleration to a new location
Occur 3 x per second
Allow us to go rate points of interest

73
Q

What are smooth pursuit eye movements

A

Tracking movement
Characterised by constant velocity at the same speed of target
Allow us to track an item of interest (often seen with a saccades) and then tracked with smooth pursuit

74
Q

What drives saccades to be the same

A

The spatial temporal tuning of perception and mechanisms

75
Q

Why should we move our eyes

A 
The fovea (part of retina) contains central vision that has the highest density of photoreceptors and largest overlap of receptive fields 
The more photoreceptors to receive sensory input, the more info is available to process, results in high acuity
76
Q

What did Yarbus 1967 find

A

Participants looked at photos and were given instructions such as “look at how weatlthy the ppl are in the photo”
Questions guided where people’s fixated on
Ppl looked at faces then objects in room
Showed saccades are not random

77
Q

What is the sequential information maximisation model

A

After each fixation the next fixation will be at a location that minimises uncertainty and maximises info

78
Q

Distance between 1st saccades and hand?

A

1.5 degrees

79
Q

How is the superior collicukus involved in selecting a new target

A

It mediates target selection
Mid brain structure, integrates visual, auditory and somatosensory spatial info to intimate orienting movement of hand and eyes
Part of circuits for visual processing and deployment of saccades
Info is combined to become a single type of info

80
Q

What happens when frontal eye fields are stimulated

A

Results in an automatic deployment of covert attention which improves performance
Ability to select a target is decreased is superior collicukus is inactive

81
Q

5 key points about bottom up attentional deployment

A
  1. Stimuli depends on context e.g. colour can depend on what colour is next to it
  2. Saliency map plausible and efficient bottom up strategy
  3. People tend to move on from a spot and not return (inhibition of return)
  4. Attention and eye movements tightly coupled- poses computational challenges to coordinate system used to control attention
  5. Seeing and understanding an object makes you look it it for shorter time or longer time (longer if u don’t recognise it)
82
Q

Top down pathways?

A

You have a cognitive goals in mind to do something e. G. Pick up water bottle

83
Q

Bottom up control

A

A stimulus had a feature that captures our attention

You make a saccade and attend to it

Perception and Cognition (4 decks)

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