9A - Errors of sight Flashcards

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1
Q

Fallibility definition

A

the quality of being prone to error or experiencing difficulties in judgement

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2
Q

Fallibility of perception

A

Our perceptual systems are subjective (unique to you) and prone to error (bias). These errors in the judgement or interpretation of sensory stimuli can be considered perceptual distortions

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3
Q

Perceptual distortion definition

A

an error in the judgement of interpretation of sensory stimuli

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4
Q

Visual illusion definition

A

the perception of a visual stimulus that conflicts with how it is in physical reality
- a consistent misinterpretation of real sensory information

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5
Q

Why do we see illusions?

A
  • The physical nature of the visual stimulus
  • The characteristics of the eyes
  • The characteristics of our visual perceptual process
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6
Q

Examples of visual illusions

A
  • Müller - Lyer illusion
  • Ames room illusion
  • Ponzo illusion
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7
Q

Müller - Lyer illusion definition

A

an illusion where the length of the central line of a stimulus is misjudged because of the lines attached to either end of the stimulus

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8
Q

Müller - Lyer illusion explanation - Biological

A

Eye movement theory: The arrow head and the feather tail head require different types of eye movement in the sensation process, therefore the two shapes/lines are physically perceived differently.
- This theory however is outdated and has been disproven!

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9
Q

Müller - Lyer illusion explanation - Psychological

A

Carpenter world hypothesis: suggests that the Müller - Lyer illusion is perceived because the lines at the end of the stimuli imply depth due to our frequent past experience with right angles.

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10
Q

Müller - Lyer illusion explanation - Social

A

The social/cultural reasons such as past experience and social environment.
- e.g. people who live in undeveloped countries without buildings etc. aren’t as familiar with angled shapes and architecture, therefore may not fall for the illusion due to lack of past experience

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11
Q

Ames room illusion definition

A

an illusion that causes difficulty in accurately perceiving size based on an apparatus that manipulates depth cues

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12
Q

Ames room illusion explanation - How is the room built?

A

The room appears rectangular because secondary (pictorial) depth cues are manipulated by the room.
- The room slopes up and outward as lines move further from the observer, to compensate for linear perspective
- This effect is strengthened by distorting the appearance of objects in the room (such as clocks, pictures and floor tiles) so that they look the same size and shape on both sides of the room to the observer

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13
Q

Ames room illusion explanation - What happens to perception?

A

We maintain the shape consistency of the room as rectangular at the expense of the size constancy of the people inside the room.
- The observer applies perceptual set from their past experience of rooms being rectangular, not trapezoidal
- Thus, people in the far corner appear to be the same distance from the observer as the objects in the nearer corner
- The peephole allows us to only use one eye to look into the room

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14
Q

Ponzo illusion definition

A

an illusion where diagonal lines converge above two parallel lines leads observers to misjudge the length of the parallel lines

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15
Q

Ponzo illusion explanation

A
  • The Ponzo illusion is perceived because of a misapplication of the pictorial depth cue of linear perspective
  • Because we expect parallel lines to converge as they recede into the distance, the diagonal stimuli have depth implications
  • The top parallel line is then perceived to be further away and the bottom line is closer to the observer
  • As the two lines cast the same sized retinal image, but the top line is perceived as being further away from the observer, it is perceived as being longer than the bottom line (and vice versa)
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16
Q

Agnosia

A
  • agnosia usually occurs as the result of a brain lesion (stroke, dementia, brain injury, brain tumour, or overexposure to a toxin)
  • visual agnosia is commonly associated with brain lesions that occur in the parietal lobe, temporal lobe, and occipital lobe (key lobes for visual perception)
17
Q

Agnosia definition

A

a disorder involving the loss or impairment of the ability to recognise familiar stimuli through the use of one or more senses, despite the senses functioning normally otherwise

18
Q

Agnosia affects recognition of:

A
  • Vision (visual agnosia)
  • Smell (olfactory agnosia)
  • Sound (auditory agnosia)
  • Touch (tactile agnosia)
  • Taste (gustatory agnosia)
19
Q

There are two main categories of visual agnosia

A
  1. Apperceptive visual agnosia
  2. Associative visual agnosia
20
Q

Apperceptive visual agnosia definition

A

the inability to generate holistic perceptions of visual information
- this represents a failure of perception

21
Q

What it involves - Apperceptive visual agnosia

A
  • difficulty in perceiving visual information
  • intact mental understanding of what objects look like
  • inability to identify objects is caused by a difficulty in perceiving the form or visual elements of an object
  • otherwise normally functioning vision
22
Q

Associative visual agnosia definition

A

the inability to identify or recognise a visual stimulus. The perception is in fact, but the ability to interpret this meaningfully is compromised

23
Q

What it involves - Associative visual agnosia

A
  • Difficulty in identifying what object is being viewed
  • No difficulty in perception; individuals are able to identify the individual visual elements of objects
  • Identification difficulties stem from being unable to link prior experience to the object they are viewing
  • Otherwise normally functioning vision
24
Q

Subtypes of visual agnosia

A
  • Prosopagnosia
  • Achromatopsia
  • Simultanagnosia
  • Topographagnosia
  • Agnostic Alexia (Pure Alexia)
25
Q

Subtypes of visual agnosia - Prosopagnosia

A

the inability to recognise familiar faces

26
Q

Subtypes of visual agnosia - Achromatopsia

A

the inability to distinguish between colours

27
Q

Subtypes of visual agnosia - Simultanagnosia

A

the inability to recognise multiple objects in the same visual scene at the same time

28
Q

Subtypes of visual agnosia - Topographagnosia

A

the inability to process spatial environments including familiar places

29
Q

Subtypes of visual agnosia - Agnostic Alexia (Pure Alexia)

A

the inability to recognise or interpret written words