Psychology of visual perception Flashcards
1
Q
How do we see briefly
A
- Light from environment projected onto retina
- Photoreceptors transform into electrical impulses
- Transmitted vis optic nerve to cisual cortex
2
Q
WHta is perception
A
- Combining nerual signals with previous knowledge/ experience to interpret and store as mental representation (percept)
- Good understanding of how incoming informaiton broken down and analysed: but not how put back together tof orm perceptual experience- known as binding porblem
- Active process that allows us to recognise, locate and detect
3
Q
Visual association area
A
4
Q
Visual Perception
A
- Brain damage in visual association areas can affect perceptual processes
- Visual agnosis -‘unable to know’:
- Apperceptive agnosia - csnnot recognise by shapem, cannot copy drawings
- Associative agnosia - can copy shapes, cannpt assoication meainign with shapes
- Prosopagnosia - unable to recognise faces
- Capgras syndrome - unable to recognise known people,m belive they have been replaced by an imposter
5
Q
Perceptual processing
A
- Bottom-up: based on analyses of details in stimuli that are present (eg colour, orientation, size)
- Top-down: based on information provided by context in which stimulus is encountered, past experiences, existing knowledge.
6
Q
Porcess of perception stages
A
- Selection of information
- Organisation of information
- Inteprretation of information
7
Q
Selection of infromation in perception:
A
- External environment too detailed to process everything - need to be selective
- Selection driven by attention and filters out irrelevant stimuli to avoid ‘overload’
- Attend to information relevent to current goals (or emtoionally signficant)
- Selection can be:
- Bottom up (datat dtiven, based on light, sound, spatial location)
- Top down (conceptually driven, based on meaning)
- Allows us to be focused and to multi-task - multi-tasking is actually rapdi tasking switching, only automatic processes can occur in parallel
- Selective attention affected by fatigue and stress
- ]Most clinical errors due to frailty of human thinking under ocnditions of complexity, uncertainty and pressure of time
- Ergonomic design aims to compensate - only so much it can do, cant help you with selective attnetion.
8
Q
Selective attention
A
- Inattentional blindess - dailure ot perceive fully visible stimuli if not selected/attended too
- Change blindness - failure to perceive a substantial visual change
- Eye tracking evidence shows we can look directly at stimuli and still not perceive it.
9
Q
Organisation in Perception
A
- Tend to organise visual informaiton into patterns based on certain principles
- Automatically make assumptions about ismplesy organisation
- In uncertainty we switch interpretations - delay decision making.
- There ar edifferent principles
10
Q
Gestalt principles of organisation
A
- Closure - we see things as complete wholes rather than segmented parts
-
Continuation - we interprety things to look like smooth continuities rather than abrupt changes
- Eg, kaniza triangle - we perceive a traingle rather than 3 ‘pacman’shapes even tho there is no triange
- Proximity - elements placed together are perceived to be part of the same object rather than seperate ie, we see columns of stars rather than just seperate stars placed near each other
- Similarity - objects thay look the same are perceived a sbeign together - “birds of a feather flock together’. The spots which look similar are grouped and thism, combined with proximity makes us see lines of spots rather than a group of different coloured spots.
- Focused on Law of Pragnanz - “ov several geometrically proximal organisation…one will acvtually occur which possesses the best, simplest and most stable shape”. WHta we see is the simplest and most stable interpretation of the elements. Law of gestalt organisation were based on this law.
11
Q
Organisation in percetion
A
- Gestalt theory of visual perception - based on grouping, whole is greater than sum of its part
- Sometimes we miss the parts in seeing the whole
- clinicians frame information into clinically menaingful diagnosis
- vital signs and symptoms which dont fit pattern shouldnt be overlooked.
12
Q
Interpretation of perception
A
- Information gathered from stimulus and surrounding cues - you then interpret what tou are seeing. Information can conflict
- Perception is not complete replication of visual world. Eg room set up wiht angles etc and dependign on view you can see different sizes of people.
- Ambiguous figures - different interpretations possible when cues are restricted. Depend more on top-down processing than bottom up
- Perception foes not only depend on cues from visual field (bottom-up)
- It is a constructive, top-down pocess based on centrla processing of informaiton in association areas of the brain
- We make hypotheses based on various factors and cues
13
Q
A
14
Q
Size and shape constancy in perception
A
- if we use surorudnign cues to interpret things we can see/make mistakes.
- Babies can match the visual shapes they can touch/feel.see from around 6-8weeks
- Chimpanzes raised in dark lose the use of cells in visual cortex
- kittens raised in box showing only one orientation of lines, cant perceive (and so bump into) other orientations of line
15
Q
Perceptual bias
A
“A predisposition to interpret a stimulus a cetain way”
- Context and past experience
- Expectancy-set
- Instruction and framing effects
- Motivation (Hungerm thirst, sex)
- Emotion (anxiety, depression, anger)
- Field dependance
Perceptual bias can lead to perceptual error
23
Q
Role of experience with perception
A
- We can interact wiht novel stimuli (things) but understandign happens later
- We need to ecperience before we can understand
- We need to understand before we can interact effectively
- Recognising faces or objects is not enough - familiarity is needed
- Ditto mvoement = not just faces, we learn to interpret
24
Q
Strength of visual perceptual experience
A
- McGurk effect
- Demonstrates interaction between visual and speech perception:
- Illusion occurs when visuala nd audio information conflict
- In case of ambiguity, visual perception take spriooirty but can still be fooled because it isnt in isolationw ith everythign else and bets gues shypothesis.
- Rubber hadn illusion- perception can make you believe a different hand is your own
- Visuon is primary but in conjuction with other senses as we combine sensory information.
