Blindsight You move about the world without bumping into things
You see where things are and you can reach out and grab them What
if I told you that your brain doesnt really care if youre aware
that you are doing these things!?
Slide 2
Blindsight and the Dorsal Stream Lesions (usually due to
stroke) in primary visual cortex cause a region of blindness called
a scotoma Identified using perimetry X
Slide 3
Blindsight and the Dorsal Stream Patients with lesions to
primary visual cortex occasionally retain some visual abilities:
better than chance performance on forced-choice discrimination
tasks spatial navigation and coordination (i.e. avoid obstacles,
interact with environment)
Slide 4
Blindsight and the Dorsal Stream Patients with lesions to
primary visual cortex occasionally retain some visual abilities:
better than chance performance on forced-choice discrimination
tasks spatial navigation and coordination (i.e. avoid obstacles,
interact with environment) Thought to be because of other backdoor
pathways that send signals to the Dorsal Stream, A.K.A the Where
and How Pathway
Slide 5
Blindsight and the Dorsal Stream The Dorsal Stream is thought
to mediate much spatial processing and interaction with the
environment WHAT WHERE
Slide 6
Blindsight and the Dorsal Stream The Dorsal Stream is thought
to mediate much spatial processing and interaction with the
environment But the neural activity in these structures does not
(is not alone sufficient to) enter into consciousness
Slide 7
The Hard Problem Returns MYSTERY: what is special about neural
activity that leads to awareness ? NOBODY KNOWS !
Slide 8
Perception Without Awareness Blindsight is just one example of
perception without awareness Using sensory information without
entering it into the contents of consciousness Masked Priming is
another example
Slide 9
Masked Priming S P A M TIME
Slide 10
XXXXX Masked Priming S P A M TIME
Slide 11
S P _ _ XXXXX Masked Priming S P A M TIME
Slide 12
Masked Priming Tricky problem: how would you design the details
of this experiment so that you can detect the effect of perception
without awarness
Slide 13
Masked Priming Subject must complete the stem to make any word
other than the word that was masked
Slide 14
Masked Priming If subjects are more likely to use masked word
this indicates subconscious influence on behavior
Slide 15
Perception Without Awareness The brain uses information without
you knowing it Does this mean that all information available to
your brain will get used by your brain? No of course not!
Slide 16
Vokey & Read S T U D Y l a n i m i l b u S s e g a s s e
M
Slide 17
Subliminal Messages What is a message Wikipedia definition: a
message is information that is sent from a sender to a
receiver
Slide 18
Subliminal Messages What is a subliminal message A message that
conveys information without triggering awareness of that
information in the receiver
Slide 19
Two Themes What were the two themes of this article? 1. Do
so-called subliminal messages work? 2. Is it possible that not all
messages were put there by evil rock stars (or Satan)?
Slide 20
Subliminal Messages What two kinds of subliminal messages do
the authors investigate?
Slide 21
Subliminal Messages What two kinds of subliminal messages do
the authors investigate? backmasking - backwards messages in
songs
Slide 22
Subliminal Messages What two kinds of subliminal messages do
the authors investigate? backmasking - backwards messages in songs
words embedded in the background of images
Slide 23
Backmasking Backmasking is not backward masking Backward
masking is a visual illusion that is robust and well studied (if
youre going to argue that some perceptual phenomenon is the work of
Satan, at least get the name right)
Slide 24
Backmasking controversy in the 80s - subliminal backmasked
messages in rock music
Slide 25
Backmasking Examples of Gary Greenwalds demonstrations
(warning: you are about to hear a backmasked message)
ForwardBackward
Slide 26
Does Backmasking Work? What can subjects tell about backwards
messages?
Slide 27
Does Backmasking Work? What can subjects tell about backwards
messages? Sex of the speaker Language (barely) Different speaker
(barely)
Slide 28
Does Backmasking Work? What dont backwards messages
convey?
Slide 29
Does Backmasking Work? What dont backwards messages convey?
Meaning
Slide 30
Does Backmasking Work? Some Examples of the experiments that
Vokey & Read did: Subjects were presented with various phrases
played backward. Subjects were unable to: Accurately discriminate
between questions and declarations Sort sentences into the category
of message (i.e. satanic, christian, nursery rhymes, etc.)
Slide 31
Does Backmasking Work? The meaning of backmasked messages is
not consciously perceived (sufficiently to enable performance on
these tasks). Might such messages still influence behavior?
Slide 32
Does Backmasking Work? Priming by backmasked message?
Slide 33
Does Backmasking Work? Priming by backmasked message? Subjects
presented with passages that use the less common of two homophones
tend to use that word when asked to spell it e.g. climbing Mt.
Everest is an incredible feat
Slide 34
Does Backmasking Work? Priming by backmasked message? Subjects
presented with passages that use the less common of two homophones
tend to use that word when asked to spell it e.g. climbing Mt.
Everest is an incredible feat Subjects heard backwards sentences
containing uncommon words If backwards messages have subliminal
influence, what would you predict?
Slide 35
Does Backmasking Work? Priming by backmasked message? Result:
there was no biasing of the less frequent homophone by exposure to
it in a backward message
Slide 36
Does Backmasking Work? Priming by backmasked message? Result:
there was no biasing of the less frequent homophone by exposure to
it in a backward message Interpretation: backmasked messages are
not effective at influencing behavior
Slide 37
Does Backmasking Work? Priming by backmasked message? What are
some counterarguments one might make?
Slide 38
Does Backmasking Work? Priming by backmasked message? What are
some counterarguments one might make? Perhaps repeated exposure is
necessary
Slide 39
Does Backmasking Work? Priming by backmasked message? What are
some counterarguments one might make? Perhaps repeated exposure is
necessary Null findings do not prove the absence of an effect
Slide 40
Does Backmasking Work? Priming by backmasked message? What are
some counterarguments one might make? Perhaps repeated exposure is
necessary Null findings do not prove the absence of an effect one
needs to know the statistical power
Slide 41
Are All Subliminal Messages Intentionally Inserted? These
messages tend not to be clear and obvious
Slide 42
Are All Subliminal Messages Intentionally Inserted? These
messages tend not to be clear and obvious Could it be that our
brains mistakenly see or hear messages that arent really
there?
Slide 43
Are All Subliminal Messages Intentionally Inserted? These
messages tend not to be clear and obvious Could it be that our
brains mistakenly see or hear messages that arent really there? Do
brains make stuff up!?
Slide 44
Are All Subliminal Messages Intentionally Inserted? These
messages tend not to be clear and obvious Could it be that our
brains mistakenly see or hear messages that arent really there? Do
brains make stuff up!? Absolutely! All the time.
Slide 45
Are All Subliminal Messages Intentionally Inserted? Is there
really a dog or are the spots enough like a dog for your brain to
fill in the rest?
Slide 46
Are All Subliminal Messages Intentionally Inserted? Some other
examples you already know about : Missing fundamental, color
constancy, size constancy, the Kaniza triangle, stereo depth, the
blindspot, illusory conjunctions
Slide 47
Subliminal Messages Where you Least Expect Them How did Vokey
and Read test the idea that subliminal messages might just be a
case of mistaken perception?
Slide 48
Subliminal Messages Where you Least Expect Them They examined
passages from various sources (Jabberwokey and the 23rd Psalm)
played backwards to identify candidate messages The subliminal
message is:
Slide 49
Subliminal Messages Where you Least Expect Them They examined
passages from various sources (Jabberwokey and the 23rd Psalm)
played backwards to identify candidate messages The subliminal
message is: saw a girl with a weasel in her mouth
Slide 50
Subliminal Messages Where you Least Expect Them Listeners were
given each passage (backwards) and asked to listen for 12 possible
messages Listeners detected messages in the appropriate passage
when primed to expect it
Slide 51
Subliminal Messages Where you Least Expect Them Interpretation:
Your brain is remarkably good at active construction of patterns
amid a background of noise.