Psychology of vision Flashcards
what is seeing
Light from the environment is projected onto the retina
Photoreceptors transform this image into electrical impulses
These are then transmitted via the optic nerve to the visual cortex
what is perceiving
how does attention affect our vision
better vision if our attention is on it
we attend to what aligns with our behavioural goals
visual association areas
Link between the cortices (occipital and parietal)
Brain damage in visual association areas can affect perceptual processes i.e. develop visual agnosias abd capragas syndrome
- visual agnosia
- apperceptive agnosia
- associative agnoisa
- proopagnosia
- capragas syndrome
- unable to know
- cannot recognise by shape, cannot copy drawings
- cannot copy shapes, cannot associate shapes w meaning
- unable to recognmise faces
- capragas syndrome- inability to recognise known people, believing that they have been replaced by imposters
perceptual processing
- bottom-up processing
- top-down processing
bottom up- based on analyses of details in stimuli that are present (e.g., colour, orientation, size)
top down processing- based on information providd by context in which stimuli are encountered, past experiences, existing knowledge
3 steps of perception processing
- Selection of information
- Organisation of info
- Interpretation of info
selection on info (1st step of perception processing)
- attention is finite and the external environment is too detailed to process everything so we filter out irrelevant info to avoid overload.
- we attend to info that is either relevant to current goals or is emotionally significant
- allows us to be more focussed and multitask
- selction can be bottom up (sound, location etc.) or top down (based on connections and context)
- includes selective attention
selective attention
- inattentional blindness
- change blindness
inattentional blindness- failure to perceive fully visible stimuli if it is not selected/ attended to \
substantial change is required to elicit a substantial visual change
Most clinical errors are due to frailty of human thinking under conditions of complexity, uncertainty and pressure of time
organisation (2 of the process of perception)
Tend to organise visual information based on patterns and certain principles
Automatically make assumptions based on simplest organisation
Bistable percept- stable in 2 states (Appearances )
In uncertainty we switch interpretations
includes: gastalt principles of organisation and the law of pragnanz
gestalt principles of organisation
- Closure—– we see things as complete whole rather than segmented parts
- Continuation—- we interpret things to look like smooth continuities rather than abrupt changes
- Proximity—- objects placed together are perceived to be part of the same object rather than separate ones (see columns of stars rather than just separate ones)
- Similarity-—— objects that look the same are perceived as beinf together
sometimes we miss the parts to see the whole, clinicians frame information into a clinically meaningful diagnosis, vital signs and symptoms which don’t fit pattern shoukdnt be overlooked
the law of pragnanz
Whgat we see is the simplest and most stable interpretation of the elements
Gestalt organisation is based on this
interpretation (3rd stage of the perceiving process)
percept is not a complete replication of the visual world
information is gathered from stimulus and surrounding cues
ambiguous figures- different interpretations are possible when cues are restricted
perceiving depends more on top down processing than top up
perceptual bias
A predisposition to interpret a stimulus in a certain way
instruction and framing effect
motivation (hunger, thirst)
emotion
field dependance
perceptual bias can lead to perceptual error
perceptual bias- expectancy
expectancy can be created which influence interpretation
Expectations can bias diagnosis
