Visual Knowledge and Imagery Flashcards
mental imagery
experienceing a sensory impression in the absence of sensory input
visual imagery
seeing in the absence of visual stimulus
how is visual imagery useful
provides a way of thinking that adds another dimension to purely verbal techniques can imagine with other sense too -auditory -smell -taste -tactile experiences
imagery and the cognitive revolution
developed ways to measure behaviour that could be used to infer cognitive processes
paired-associate learning
paivio cognitive revolution and imagery
paivio
-memory for words that evoke mental images (concrete nouns) is better than those that do not (abstract nouns)
shepard and meltzer, imagery and the cognitive revolution
mental chronometry
participants mentally rotated one object to see if it matched another object
one of the first quentitative studies of imagery
suggested imagery and perception may share the same mechanisms
mental rotation task - the further the distance, the longer it takes. seen in both rotation in depth and plane
mental scanning
spatial correspondence between imagery and perception
scanning and acuity
we act as if our mental images are physical entities
scannin like kosslyns boat
acuity like elephat / rabbit / fly experiment
kosslyn’s boat
memorize picture, create an image of it
in image move from one part of the picture to another eg anchor to cabin
it took longer for participants to metnally move long distances than shorter distances
conc like perception, imagery is spatial
lea explanation of scanning results
more distraction when scanning longer distance may have increased reaction time
demo - scanning california maybe listen for conclusions
kosslyn et al’s islands
island with 7 locations, 21 possible trips
it took longer to scan between greater distances
conc - visual imagery is spatial, even when distractions are equated
is imagery spatial or propositional
pylyshyn
spatial representation is an epiphenomenon
-accompanies real mechanism but is not actually part of it = external lights flashing on a computer
proposed that imagery is propositional - can be represented by abstract signals and language
how does Pylyshyn explain kossylns boat
tacit-knowledge explanation
suggests people use real-world knowledge unconsciously and it influences imagery
eg we know it takes longer to drive bigger distances
finke and pinker view of is imagery spatial or positional
participant judge whether arrow points to dots previously seen
longer reaction time when greater distance between arrow and dot (as if they were mentally throwing)
not instructed to use visual imagery
no time to memorize, no tacit knowledge
comparing imagery and perception
relationship between viewing distance and ability to perceive details
-imagine small animal next to larger animal
-quicker to detec details on the larger animal
faster to answer question about whiskers on the rabit when comapred to a fly than an elephant
mental-walk task
how close can you get to your image until it overflows your visual field?
move closer to small animals than to large animals
images are spatial, like perception
perky study looking at interactions of imageyr and perception
project mental image onto screen
very dim (below conscious level picture
-particiaptns likely to confuse actual picutre and their mental image
farah study looking at interactions of imagery and perception
imagery affected perceptual task
letter visualisatoin experiment
participant visualises H or T on the screen
then flash A
then letter flashed on either left or right side of screen
participant has to determin whether the test letter was flashed in the first or second square
results = accuracy was higher when the letter was the same as the one that had been imagined
category specific neurons
imagery neurons respond to both perceving and imaging an object
-located in medial temporal lobe
same response of neuron to both imagery and perception
leBihan et al brain activation
overlap in brain activation for perception and imagery in visual cortex
complex overlap of activation
differences near back of the brain
amedi and coworkers also looking at imagery and perception
again overlap
deactivation of non-visual areas of the brain
-hearing
-touch
mental images are more fragile, less activation keeps other things from interfereing
brain activity in response to imagery
may indicate something is happening
may not cause imagery
how to prove a causal mechanism?
transcranial magnetic stimulation
decreases brain functioning in parituclar area of the brain for a short time
if behaviour is disrupted the deactivated part of the brain is causing that behaviour
(another way to explore is to use neurocortical legions)
kosslyn and TMS
TMS to visual area of brain during eprception and imagery task
response time slower for both
brain activity in visual area of brain plays a causal role for both perception and imagery
patient MGS
had a portion of her right occipital lobe removed as a treatment for epilepsy
farah et al measured her performance on the mental walk task before and after surgery
after surgery the size of her visual field was reduced and she could mentally approach only to wihtin 35 feet (before was 15)
unilateral neglect
patient ignores objects in one half of visual field in perception and imagery the italian street
neglect pattern occurs for metnal images the same way it does for visual perception
guariglia and coworkers on imagery and perception damages
brain damaged patient
patients perceptions intact but mental images were impaired (italian street task)
dissociation between imagery and perception instead of the overlap seen before
patient RM
perception intact, imagery impaired
damage to occipital and parietal lobes
could draw accurate pictures of objects in front of him
could not draw accurate pictures of objects from memory
patient CK
imagery intact, perception impaired
inability to name pictures of objects, even his own drawings, in front of him
could draw objects in great detail from memory (using imagery)
making sense of neuropsychological results
evidence for double dissociation between imagery and perception
- indicates separate mechanisms
also evidence for shared mechanisms - shared deficits in many patients
how can both findings be explained?
behrmann and coworkers on making sense of neuropsychological results
mechanisms still partially overlap
visual perception involved bottom-up processing located at lower and higher visual centres
imagery is a top down process; located at higher visual centres
explains ck and rm but not mgs
These locations can explain why C.K. has a perceptual problem but can still create images, and why R.M. has trouble creating images but can still perceive.
so actual object to receiving area to higher visual areas to memory storage
perception is the bottom up arrow and imagery is the top down
differences in experience
perception is automatic and stable
imagery takes effort and is fragile
chalmers and reisberg
had participants create mental images of ambigious figures
difficult to flip form one perception to another wile holding a mentla image of it
eidetic imagery
photographic memory
extremely rare
found in some autistic individuals
more common in kids than adults
what is an epiphenomenon
something that goes along with a process but isnt really part of it
