Blindsight

Blindsight Blindsight - Start

2016-07-22 77K 77 0 0

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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 doesn’t really care if you’re aware that you are doing these things!?. ID: 414504 Download Presentation

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Blindsight




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Presentations text content in Blindsight

Slide1

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 doesn’t really care if you’re aware that you are doing these things!?

Slide2

Blindsight

and the Dorsal Stream

Lesions (usually due to stroke) in primary visual cortex cause a region of blindness called a scotomaIdentified using perimetry

X

Slide3

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)

Slide4

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”

Slide5

Blindsight and the Dorsal Stream

The Dorsal Stream is thought to mediate much spatial processing and interaction with the environment

“WHAT”

“WHERE”

Slide6

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

Slide7

The Hard Problem Returns

MYSTERY: what is special about neural activity that leads to awareness ?

NOBODY KNOWS !

Slide8

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

Slide9

Masked Priming

S P A M

TIME

Slide10

XXXXX

Masked Priming

S P A M

TIME

Slide11

S P _ _

XXXXX

Masked Priming

S P A M

TIME

Slide12

Masked Priming

Tricky problem: how would you design the details of this experiment so that you can detect the effect of perception without

awarness

Slide13

Masked Priming

Subject must complete the stem to make any word

other than

the word that was masked

Slide14

Masked Priming

If subjects are more likely to use masked word this indicates subconscious influence on behavior

Slide15

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!

Slide16

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

Slide17

Subliminal Messages

What is a “message”Wikipedia definition: “a message is information that is sent from a sender to a receiver”

Slide18

Subliminal Messages

What is a “subliminal message”

A message that conveys information without triggering awareness of that information in the receiver

Slide19

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)?

Slide20

Subliminal Messages

What two kinds of subliminal messages do the authors investigate?

Slide21

Subliminal Messages

What two kinds of subliminal messages do the authors investigate?

“backmasking” - backwards messages in songs

Slide22

Subliminal Messages

What two kinds of subliminal messages do the authors investigate?

“backmasking” - backwards messages in songs

words embedded in the background of images

Slide23

Backmasking

Backmasking

” is

not

backward masking

Backward masking is a visual illusion that is robust and well studied

(

if you’re going to argue that some perceptual phenomenon is the work of Satan, at least get the name right)

Slide24

Backmasking

controversy

in the 80’s - subliminal “

backmasked

” messages in rock music

Slide25

Backmasking

Examples of Gary Greenwald’s demonstrations (warning: you are about to hear a backmasked “message”)

Forward

Backward

Slide26

Does Backmasking Work?

What can subjects tell about backwards messages?

Slide27

Does Backmasking Work?

What can subjects tell about backwards messages?

Sex of the speaker

Language (barely)

Different speaker (barely)

Slide28

Does Backmasking Work?

What don’t backwards messages convey?

Slide29

Does Backmasking Work?

What don’t backwards messages convey?

Meaning

Slide30

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.)

Slide31

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?

Slide32

Does Backmasking Work?

Priming by backmasked message?

Slide33

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

Slide34

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 ite.g. climbing Mt. Everest is an incredible featSubjects heard backwards sentences containing uncommon words

If backwards messages have subliminal influence, what would you predict?

Slide35

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

Slide36

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

Slide37

Does Backmasking Work?

Priming by backmasked

message?

What are some counterarguments one might make?

Slide38

Does Backmasking Work?

Priming by backmasked message?

What are some counterarguments one might make?

Perhaps repeated exposure is necessary

Slide39

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

Slide40

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

Slide41

Are All Subliminal Messages Intentionally Inserted?

These messages tend not to be clear and obvious

Slide42

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 aren’t really there?

Slide43

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 aren’t really there?

Do brains make stuff up!?

Slide44

Are All Subliminal Messages Intentionally Inserted?

These messages tend not to be clear and obviousCould it be that our brains mistakenly see or hear messages that aren’t really there? Do brains make stuff up!?

Absolutely! All the time.

Slide45

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?

Slide46

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

Slide47

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?

Slide48

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:

Slide49

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”

Slide50

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

Slide51

Subliminal “Messages” Where you Least Expect Them

Interpretation: Your brain is remarkably good at “active construction” of patterns amid a background of noise.

Slide52

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