14.1 Seeing is perceiving Flashcards
1
Q
How are we able to see? (steps)
A
- Light from environment projected onto retina
- Photoreceptors transform into electrical impulses
- Transmitted via optic nerve to visual cortex
- Image of visual pathways
2
Q
What is perceiving?
A
- Combining neural signals (bottom-up)with previous knowledge/experience (top-down) to interpret & store as mental representation (percept)
- Everyone’s perception is DIFFERENT
- Depends on behavioural goals & experiences
- Everyone’s perception is DIFFERENT
- Active process that allows us to recognise, locate & detect
3
Q
What is the binding problem?
A
- Good understanding of how incoming information broken down & analysed
- But NOT how put back together to form perceptual experience
4
Q
What is the visual association area?
A
Is a linking system
5
Q
What can brain damage in visual association areas afffect in perceptual processes?
A
-
Visual agnosias - ‘unable to know’
-
Apperceptive agnosia
- Cannot recognise by shape
- Cannot copy drawings
- Associative agnosia
- Can copy shapes
- Cannot associate meaning with shapes
-
Prosopagnosia
- Unable to recognise faces
-
Apperceptive agnosia
6
Q
What is Capgras syndrome?
A
-
Unable to recognise known people
- Believe they have been replaced with an imposter
- MORE common in women & children
- INCREASE association with Alzeihmer’s & dementia & schizophrenia
7
Q
What are the types of perceptual processing & explain them
A
-
Bottom-up
- Based on analyses of details in stimuli that are present (e.g. colour, orientation, size)
-
Top-down
- Based on information provided by context in which stimulus is encountered, past experiences, existing knowledge
8
Q
What are the stages in perception & explain them?
A
-
Selection
- External environment too detailed to process everything
- Have to be selective
- Selection driven by attention & filters out irrelevant stimuli to avoid ‘overload’
- Allows us to focus
- Attend to information relevant to current goals (or emotionally significant)
- Selection can be:
- Bottom up (data driven, based on light, sound, spatial location)
- Top down (conceptually driven, based on meaning)
- Affected by fatigue & stress
- External environment too detailed to process everything
-
Organisation
-
Tend to organise visual information into patterns based on certain principles
-
Gestalt theory of visual perception
- Based on ‘grouping’
- Whole is greater than sum of its parts
-
Gestalt theory of visual perception
- Automatically make assumptions about simplest organisation
- Sometimes we miss the whole
- Hence, clinicians get a second opinion as may miss something
- In uncertainty we switch interpretations – delay decision making?
-
Tend to organise visual information into patterns based on certain principles
-
Interpretation
- Information gathered from stimulus & surrounding cues
- Information can conflict
- Relative to background information so when brain conflicts, brain makes hypothesis of what it sees
-
Ambiguous figures (hard to understand)
- Different interpretations possible when cues are restricted
- Depend more on top-down processing than bottom-up
9
Q
What are the failures with selective attention?
A
-
Inattentional blindness
- Failure to perceive fully visible stimuli if not selected/attended to
-
Change blindness
- Failure to perceive a substantial visual change
- Eye-tracking evidence shows we can look directly at stimuli & still not perceive it
10
Q
What is multi-tasking?
A
- Is rapid task switching
- Only automatic processes can occur in parrallel
11
Q
What are Gestalt principles of organisation?
A
-
Closure
- We see things as complete wholes rather than segmented parts (even though they don’t exist)
-
Continuation
-
We interpret things to look like smooth continuities rather than abrupt changes
- E.g. Kanizsa triangle
- We perceive a triangle rather than 3 ‘pacman’ shapes
- Even though there is no triangle!
-
We interpret things to look like smooth continuities rather than abrupt changes
-
Proximity
-
Elements placed together are perceived to be part of the same object rather than separate ones
- i.e. we see columns of stars rather than just separate stars placed near each other
-
Elements placed together are perceived to be part of the same object rather than separate ones
-
Similarity
-
Objects that look the same are perceived as being together
- ‘birds of a feather flock together’
- The spots which look similar are grouped and this, combined with proximity makes us see lines of spots rather than a group of different coloured spots
-
Objects that look the same are perceived as being together
12
Q
What is the Law of Pragnanz?
A
- “Of several geometrically possible organisations…one will actually occur which possesses the best, simplest and most stable shape”
- What we see is the simplest** and **most stable interpretation of the elements
13
Q
What is interpretation?
A
- Perception does not only depend on cues from visual field (bottom-up)
- It is a constructive, top-down process based on central processing of information in association areas of the brain
- We make hypotheses based on various factors & cues
- These can be wrong!
14
Q
Explain size & shape constancy
A
- Learned with a best guessed hypothesis
- Can be updated with new information
- Babies can match visual shapes they can touch/feel/see from around 6-8 weeks
15
Q
What is perceptual bias?
A
-
“A predisposition to interpret a stimulus a certain way”
- Context & past experience
- Expectancy-set
- Instruction & framing effects
- Motivation (hunger, thirst, sex)
- Emotion (anxiety, depression, anger)
- Field dependence
- Perceptual bias can lead to perceptual error
