Perception Flashcards

1
Q

Why must sensory information be interpreted?

A
  1. Information is incomplete
  2. Too much raw information
  3. Must extract what is important or dangerous

-> Our brain must consciously perceive the most important info. in spite of poor quality and vast amount of unnecessary and irrelevant info.

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2
Q

Why is there a focus on vision in the study of perception?

A
  1. Large part of our brain is dedicated to vision
  2. Seeing is a difficult task and demands interpretation
  3. Vision is a good source of environment information
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3
Q

What are the 3 misconceptions about visual perception?

A
  1. It is automatic and effortless
  2. Provides exact copy of the world
  3. Provides rich and continuous visual environment
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4
Q

What are the components of visual perception in the brain?

A

> Eyes (retinas and foveas)
Optic nerves
Optic chiasma
Optic tracts
Lateral geniculate nucleus (LGN - within thalamus)
Visual (primary) cortex (in occipital lobe)

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5
Q

What are the light receptor cells and where are they located?

A

In the retina:

  • Rods: low light, not sensitive to colour info. -> black and white
  • Cones: well-lit conditions, sensitive to colour info., found in fovea
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6
Q

Why is binocular vision only possible for the middle part of the visual field?

A

Fixating an item so that it is central to visual field make information fall directly onto fovea (contains cones)
-> colour vision occurs only for items we’re directly fixating

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7
Q

Why is our mental representation of seeing all surrounding environment not in 3D colour and detail?

A

Colour vision occurs only for items we’re directly fixating

only middle part of visual field falls directly onto fovea and its containing cones

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8
Q

How does the lateral geniculate nucleus direct most of the visual information?

A

Via optic radiations towards primary visual cortex (= V1, striate cortex)

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9
Q

What are the two principles of vision?

A
  1. Vision is hierarchical

2. Vision is modular

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10
Q

What makes vision hierarchical?

A

Brain starts with simple properties (dots and lines), and interprets it into more complex information
- no clear representation of an item in V1

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11
Q

What makes vision modular?

A

Specific parts are dedicated to particular types of information

  • if V1 is damaged we become cortically blind
  • if V4 is damaged -> colour blindness
  • if V5 is damaged -> motion blindness
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12
Q

Why do we become cortically blind if the primary visual cortex (V1) is damaged?

A

It is crucial for fundamental extraction of visual input from incoming information

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13
Q

What are the two visual pathways?

A
  1. Dorsal stream
    - ‘where stream’
    - occipital -> parietal cortex
    - V1 - V5
  2. Ventral stream
    - ‘what stream’
    - occipital -> temporal cortex
    - V1 - V4
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14
Q

What would damage to parts of the ventral stream result in?

A

‘What stream’

- visual agnosia: failure to recognise objects or even simple shapes

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15
Q

How can patients with visual agnosia identify items?

A

When exploring with their hands

- it’s the combination of basic visual feature with its object-related characteristics that has been lost

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16
Q

What would damage to parts of the dorsal stream result in?

A

Disorders with spatial representational deficits

- primarily affecting the contralateral space of visual field (opposite to injury)

17
Q

How did Haxby (2009) demonstrate the functions of the ventral and dorsal streams?

A

Neuroimaging:

  • activation in dorsal stream for location judgements
  • activation in ventral stream for object recognition decisions
18
Q

Why is our visual world not an exact copy of the visual world?

A

Saccades provide integrated successive fixations across the visual field
-> illusion of stable visual world

19
Q

How did Rensink demonstrate change blindness?

A

He interleaved an original scene and a changed scene with a blank grey which causes a flicker

  • flicker = motion across the whole image as it’s flashing up
  • > masks the transient motion associated with the change in image directly

-> moment-to-moment representation of visual field that we possess is not very detailed

20
Q

What is the blind spot present in each of our eyes?

A

No rods or cones -> no visual input processed

21
Q

Why do we have no perception of constantly missing a small part of the visual field, even though there’s a blind spot in each of our eyes?

A

Our brain gives us the mental representation of a continuous perception across the whole visual field
-> illusion

22
Q

Why is perception an effortful and intricate process?

A

> Input from the world contain insufficient information

  • > our visual system adapts by computing certain expectations that we have
  • it can overcompensate -> illusory images

> We can process little information at any one time

  • visual input contain overwhelming sensory info.
  • > attention selects relevant parts of visual field
23
Q

What happens when the visual input is ambiguous?

A

Our visual system gives us a clear interpretation of what we’re seeing

  • we can simultaneously perceive multiple possibilities of a single ambiguous image
  • our visual system automatically uses context to interpret the visual scene