NPB 014 - Illusions: Fooling the Brain Flashcards
why do we learn about illusions?
provides insights about the processing principles of the brain
what is an illusion?
a perceptual phenomenon where the percept and the physical reality are not in agreement
what are the two major problems our brains face?
nervous system develops strategies to eliminate info
we are missing sensors for certain aspects
when looking at a hollow mask making a full rotation, why does the mask appear to change direction halfway into the rotation?
top-down processing overrides visual information because brain is too used to see convex faces
what are the three types of masking
simultaneous, forward, backward
how does forward masking work
the refraction period from seeing the mask suppresses the neuron that would have signaled or processed the target
what is the critical period for forward masking
ISI, close to 0 ms
what is the critical period for backward masking
STA, around 100 ms
what makes backwards auditory masking more effective?
small gap between offset of target and onset of mask
what makes forwards auditory masking more effective?
small gap between offset of the mask and onset of target
which is more effective: forward or backward auditory masking
forward
which is more effective: tone or noise masking
noise
what makes simultaneous auditory masking more effective
as close as possible frequencies, high intensity mask
what is the masking threshold?
minimum level of stimulation needed for target to become apparent
level-dependence in auditory masking
higher intensity of mask, more masking
what is the threshold in quiet?
minimum about of stimulation we need to hear in perfect quiet
people tend to mistake the most BLANK for the most BLANK sequence.
typical, probable
SOA, STA, ISI order
SOA, ISI, STA
what role does frequency play in masking?
further the frequency, less effective the mask
utility
subjective value
what is the utility and value curve
curve upwards that plateaus
are all people risk averse?
no, gamblers
framing issue
how a question is presented changes our answers
can utility help explain the framing issue?
yes, find the point of the two options by its probability and compare it to the second answer’s utility
conjunction effect
people choose the middle point of the story, not the actual probability
neglect of base rates
people ignore the probability in favor of what seems more typical/intuitive
law of large numbers
as you increase sample size, probabilities even out
smaller of bigger hospital have more variation?
smaller hospital, relative frequency of having more boys than girls would be higher
disjunction effect
we want to know outcome before making next decision
two issues with the traditional view/
homunculus and rapid eye movements
why can’t we detect change with a blank frame?
disrupts the motion sensors
ron rensink
2 streams of visual processing and coherence theory
kevin o’reagan
the world is our outside memory, creates the illusion of “seeing”
what is spectral asymmetry?
target tones higher than mask tones make for more effective masking
how does backward masking work?
you see the first target, then by the time the mask kicks in, the after discharge of the target is suppressed by the inhibitory dip of the mask
explain how mp3 coding works for simultaneous masking
cut into frames with spectral analysis done, identify threshold in quiet, find potential maskers and filter for tones and noises and then filter those for relevant maskers, calculate individual masking thresholds then combine into a global threshold, cut what it below that
what happens for forward and backward masking in mp3 coder?
analyzes the same way ahead and behind for 2d rep
collectively exhaustive def and example
no other options than what’s given
mutually exclusive def and example
can only get one option at a time
how to represent if A, B, and C are collectively exhaustive?
P(A or B or C)=1
how to represent if A and B are mutually exclusive?
P(A and B)=0
how to calculate expected value?
probably of getting something with the number of chances you can have
absolute vs relative frequency
actual times you get something, the proportion of times you get something
how to calculate probability? (not exclusive)
P(A or B)=P(A)+P(B)-P(A and B)
how to calculate probability if mutually exclusive?
P(A or B)=P(A)+P(B)
how to calculate probability for independent events?
P(A and B)=P(A)xP(B)
how to calculate probability for conditional events?
P(A|B)=P(A and B)/(P(B))
bayes’ theorem
P(A|B)xP(B)=P(B|A)xP(A)
explain basic form of motion detector
light moves in rightward motion, first detector has delay built in, second does not. the signals from both circuits reach the detector at the same time and is processed as motion
where is the “motion detector” in our brains
retina, lgn, V1, MT (dorsal path)
what is the “delay” in our brains to detect motion
longer axons
why isn’t there motion in both directions in rotating snakes illusion
same-side pairs elicit stronger responses than opposite-side pairs
the dorsal stream leads to the BLANK cortex, the ventral stream leads to the BLANK cortex
parietal, temporal
ungerleider and mishkin thought the dorsal stream was responsible for BLANK and the ventral stream responsible for BLANK
where, what
goodale and milner thought the dorsal stream was for BLANK and the ventral for BLANK
action, perception
if you have severe damage to the ventral stream and were asked to pick up a ball and describe it, what are you able and unable to do
able to grasp it with normal opening and rotation of hand and wrist. unable to describe size, shape, orientation, etc.
how does visual information get to our cortex
image on retina, sent to the PVC (EDIT THIS SLIDE)
what happens after visual information arrives in V1 (PVC)?
goes to MT (motion-detecting neurons and generally the rest of the cortex where it matters
what is the difference between dorsal and ventral?
dorsal involves perception, while ventral is the information needed for action
what did goodale and milner find?
patient DF with damage to ventral system
what was presented in aglioti et al?
two circles, each surrounded by circlers larger or smaller than it. circles could be perceptually same or different size from each other. participants asked to reach for one of the circles and their PGA was measured
what did aglioti conclude?
grasping was unaffected by visual illusion, therefore perception and action are indeed separate
why was the aglioti experiment strange
found illusion’s effect on grasping when the discs were objectively the same size
why did pavani and franz argue against the aglioti experiment
participants were required to perceive size of both discs, but only asked to grasp one
what did the franz and pavani experiment change abt the aglioti to make it more accurate
single context and separate perceptual comparison configuration
in single context configuration, how did the illusion differ for grasping and perception trials?
they did not, effects were almost identical
when is circle-size illusion strongest?
direct comparison
what did franz and pavani find?
aglioti’s findings were mainly due to diff tasks, illusion affects perception and action similarly
how are franz and pavani different
pavani believed there is interaction between the two streams, franz believed there are no different processing mechanisms for perception and action
westwood and goodale looked at whether it matters BLANK the BLANK array is visible
when, visual
describe westwood’s vision trials
target shown for 500 ms, then request grasp, target was visible until movement onset
describe westwood’s occlusion trials
target shown for 500 ms, target was visible until immediately after grasping was requested
what did westwood and goodale find
timing matters, evidence for two streams
according to westwood and goodale, what stream works in “real time”?
dorsal
if you are asked to reach for an object that you cannot see presently but had seen before, you are using what stream?
ventral
true or false: when you rely on memory to grasp something, you are more prone to the size illusion
true
true or false: PGA is a good measure for assessing effect of illusion on grasping movement
false
who criticized use of PGA?
glover and dixon
since PGA occurs BLANK during movement, it is BLANK a good measure
late, not
what did glover and dixon find?
effect of illusion on grasping decreases over time, and PGA occurs at a time where illusion is weak. ventral susceptible to context-induced illusions, not dorsal
without vision, if you were asked to grasp an object, would your PGA be more or less affected than if you had vision
more affected
with context-induced illusions, what is the best idea?
the real time control and visibility from goodale, westwood, glover, and dixon
what is contrast?
how different luminance is from the average luminance
why is it important to static motion that we have different response latencies?
causes the delay that is necessary for coincidence to trigger motion detectors
what is contrast polarity
where exactly the contrast is, so same side vs opposite side pairs and the distance from the AL
why do we see static motion?
fast eye movement, response latencies, time delay between high contrast and lower contrast gray levels triggers motion detectors
what is traditional explanation for ventriloquist effect, why is it weak?
we thought we’re very visual, but bimodal configurations showed that we do rely on audition more than visual information sometimes
how does the ventriloquist effect happen?
quality of visual signals is better than auditory, so we perceive sound as coming from somewhere else
what did alais and burr find?
optimal estimation theory is responsible for ventriloquist effect
what is PSE
point of subjective equality, aka when 50/50 split of responses to indicate same location
when told to ignore auditory stimulus, are we really able to?
no, performance is influenced by both
when told to ignore visual stimulus, are we really able to?
yes, performance adheres to auditory
when subjects are told to attend to auditory but not visual, and visual changes, what are they most influenced by?
still audition, but confused by visual
temporal rate discrimination is more accurate in which domain?
auditory
what is a reverse ventriloquist effect?
when visual perception is influenced by auditory signals
how is PSE affected by location offset between flash and click?
EDIT THIS SLIDE
what is variance in OoTE
how trustworthy, so a more reliable tool would have lower variance
what is reliability in OoTE
how much we trust the accuracy of something
when presented with flashes and beeps, people’s perception of the number of BLANK was influenced by the number of BLANK
flashes, beeps
true or false: there is a robust effect of audition changing visual perception where auditory signal varied
false
with soft beeps, counting flashes, there was a BLANK effect on the number of flashes
weak
if you had soft beeps, but consistent flashes, you would have a BLANK effect on the counted number of beeps
weak
what role does spatial accuracy play in ventriloquist effect
visual system better with spatial accuracy, so we believe location from that system more
what is the DRM paradigm
list of word, recall the words, will usually have an unstudied word
the probability of recalling an unstudied word is about the same as recalling a word where in the list?
middle
why do we recall unstudied words in the DRM at all?
associative processes to do with the theme of the words in the list
when asked to recognize unstudied but critical words, were participants able to identify that it was a new word?
not most of them
are participants confident about seeing critical lures in the DRM?
yes
when recognizing/recalling studied vs unstudied words, Cabeza’s experiment found what differences in the hippocampus?
there’s no difference between correct or incorrect rejections/recognition, only different when rejecting or recognizing
when recognizing/recalling studied vs unstudied words, Cabeza’s experiment found what differences in the parahippocampal gyrus?
weak responses for unstudied cues because no sensory info
the hippocampus has to do with the BLANK nature of the words listed, and the parahippocampal gyrus has to do with the BLANK nature of seeing/hearing the words
semantic, sensory
what are interference effects?
EDIT THIS SLDIE
what are fluency misattributions?
how easy it is to process something (fluent) affects how easy it is to recall
what helps implant false memories?
repetition, imagination instructions/strong suggestion
why are implanted memories problematic?
interrogation/law, psychotherapy
what did lewandowsky find about false memories?
index of suspicion can contribute to whether we acknowledge retracted information
why were Americans more likely to falsely recall discovery of weapons in Iran?
suspicion overrides information retraction
what are two characteristics of false memories?
loss of detail and substitution of imagined details
what is the neural correlate of a hallucination?
neural activity in related cortex
what can cause hallucinations?
drugs, amputations/lesions, spontaneous activity in epileptic patients
explain how a hyper-excitable state comes to be
lack of activity in neurons, brain reduces threshold for activity, weak signals are now able to trigger responses
explain what a hyper-excitable state has to do with a migraine aura
neurons in visual cortex are triggered by strong visual stimulus (or spontaneously in epilepsy), starts wave of excitation (fortification pattern at leading edge), cortical spreading depression from the leading edge causes the scotoma
why is there a fortification pattern in migraine auras?
neurons have preference for a specific orientation, the pattern results from an average of the preferences of neurons in the area
what four components in mushrooms can cause hallucinations?
psilocybin, psilocin, muscimol, and ibotenic acid
subjective experience of drug-induced hallucinations depend mostly on?
set and setting (expectations and environment)
what is the relationship between serotonin and hallucination-inducing drugs?
chemical structure is similar to serotonin, stimulates serotonin receptors
how does a hyper-excitable state come to be with drugs?
large number of serotonin receptors in the raphe nuclei, which projects the high through to the thalamus, which includes the LGN, which means that there is activity going through visual cortex, causes spreading cortical depression and hallucinations
what is the penfield homunculus
the areas of the cortex dedicated to sensory information for parts of the body, which are arranged next to each other
is phantom limb phenomenon caused by a reorganization of the penfield homunculus?
no, just weak connections that used to be masked by the now missing limb are now the only ones present. these connections are connected to the other parts of the homunculus
true or false: phantom limb phenomenon does not cause a reorganization of the homunculus
false, over time there will be due to plasticity
what causes phantom pain? what are the treatments today?
activation of nerves in the stump, surgery to remove neuromas; repeated pain signals from time of injury/amputation; painkillers before amputation
