Illusion: something that is not what it appears to be
- Distinction between something being non-existent & being other than it
seems is difficult: bc
- Once you say something is not what it seems to be you may decide
you need a new word for it → you do end up replacing the old with
the new part, ( declare that the old thing doesn’t exist)
Visual illusions:
Competition between senses - vision wins
For people with little to no visions: hearing is more dominant
Vision has special status of being more closely associated with knowledge than
any other
- & language is full of metaphors
Possibility that our strong intuitions may be false
What is it like to see? What is it like to have conscious visual experience ?
You see it, you can reach out ot it
Seeming comes so naturally
Difficulty in answering questions led to conclusion that visual experience is all a
grand illusion:
- Emerged from research on change blindness & inattentional blindness to
convey the idea that our visual experience might not be as it first seems
Simple visual illusions (effects of illusory contours, brightness and colour
constancy or Müller- Lyer)
→ tricks that mislead you about what’s out there - create confusions between
appearance and reality
How vision seems?
3 themes of theories: James’s stream of visual consciousness (“the movie in the
brain” or the “vivid picture of the world we see in front of our eyes)
1) There’s rick array of conscious visual impressions to be explained
2) At any time there are definite contents of which we are aware, while
everything else remains outside of our conscious awareness.
a) Dennett rejects (when he claims that there is no show in the
Cartesian theatre)
3) Seeing means having internal mental pictures
For all: the richness of the experience is unquestioned & the in/out distinction
and underlying representation tend to be too
Idea that in seeing (& imaging) we represent the world in our minds
→ Ancient Greeks: thought about vision in terms of the world being reflected in
the pupil of the eye & imagination as picture viewing
- Conceiving of pictures inside the eye & head
Leonardo da Vinci:
- Compared the eye to a camera obscura (dark chamber) - in which an
image of the world is projected
Kepler
Optics of the eye - but said he would leave to others the job of explaining how
the image “is made to appear before the soul”
, Descartes:
(Studied actual images, thought the images are transmitted to the non-material
mind)
- Believed that pictures were transmitted through the eyes to the pineal
gland where they entered the mind
- His theory has been rejected but the idea of pictures in the head remains
popular
Cognitive psychologist: updated the idea of picture in head: internal screens or
models & pictures
Dennett:
Calls the idea of pictures in the head “an almost irresistible model of the “end
product” of visual perceptions But a “ubiquitous malady of the imagination”
Risk requiring a whole “mind-within a mind” - homunculus: little person inside
your head
3 assumptions about visions (also figure in our intuitions about vision):
1) Visual experience is richly detailed
2) There are things that are in & out of our visual experience
3) Vision operates by representing the world in the mind or the brain
If we assume all 3 we have to explain how all the neural processing in all the
parallel pathways in human visual system results in rich, definite,
representation-based conscious experience
- The basic principle is simple. If you believe that some visual
representations in the brain are conscious and others are not, then you
should be able to take examples of each and study them in detail until you
discover the difference
Filling in the gaps:
William James:
When we look around we don’t and can’t take in everything at once & yet we are
unaware of any gaps.
Why don't we notice the gaps?
- The brain fills in the missing parts
- There’s no need to fill anything in because the gaps are just a lack of info
- An absence of info is not the same as information about an absence
Amodal perception/ conceptual filling-in:
Car is conceptually completed but not visually filled in
(We don’t literally ‘see’ the hidden parts of the car, yet the car seems whole)
Blind spot: Where the optic nerve leaves the back of the eye there are no
photoreceptors, creating a blind spot on the retina that subtends about 6
degrees of visual angle, roughly 15 degrees away from the fovea
- A small object can be made to disappear from sight by lining it up
precisely on the blind spot
- If the background is boring grey → then boring grey fills the space where
the object should have been
- Distinction between something being non-existent & being other than it
seems is difficult: bc
- Once you say something is not what it seems to be you may decide
you need a new word for it → you do end up replacing the old with
the new part, ( declare that the old thing doesn’t exist)
Visual illusions:
Competition between senses - vision wins
For people with little to no visions: hearing is more dominant
Vision has special status of being more closely associated with knowledge than
any other
- & language is full of metaphors
Possibility that our strong intuitions may be false
What is it like to see? What is it like to have conscious visual experience ?
You see it, you can reach out ot it
Seeming comes so naturally
Difficulty in answering questions led to conclusion that visual experience is all a
grand illusion:
- Emerged from research on change blindness & inattentional blindness to
convey the idea that our visual experience might not be as it first seems
Simple visual illusions (effects of illusory contours, brightness and colour
constancy or Müller- Lyer)
→ tricks that mislead you about what’s out there - create confusions between
appearance and reality
How vision seems?
3 themes of theories: James’s stream of visual consciousness (“the movie in the
brain” or the “vivid picture of the world we see in front of our eyes)
1) There’s rick array of conscious visual impressions to be explained
2) At any time there are definite contents of which we are aware, while
everything else remains outside of our conscious awareness.
a) Dennett rejects (when he claims that there is no show in the
Cartesian theatre)
3) Seeing means having internal mental pictures
For all: the richness of the experience is unquestioned & the in/out distinction
and underlying representation tend to be too
Idea that in seeing (& imaging) we represent the world in our minds
→ Ancient Greeks: thought about vision in terms of the world being reflected in
the pupil of the eye & imagination as picture viewing
- Conceiving of pictures inside the eye & head
Leonardo da Vinci:
- Compared the eye to a camera obscura (dark chamber) - in which an
image of the world is projected
Kepler
Optics of the eye - but said he would leave to others the job of explaining how
the image “is made to appear before the soul”
, Descartes:
(Studied actual images, thought the images are transmitted to the non-material
mind)
- Believed that pictures were transmitted through the eyes to the pineal
gland where they entered the mind
- His theory has been rejected but the idea of pictures in the head remains
popular
Cognitive psychologist: updated the idea of picture in head: internal screens or
models & pictures
Dennett:
Calls the idea of pictures in the head “an almost irresistible model of the “end
product” of visual perceptions But a “ubiquitous malady of the imagination”
Risk requiring a whole “mind-within a mind” - homunculus: little person inside
your head
3 assumptions about visions (also figure in our intuitions about vision):
1) Visual experience is richly detailed
2) There are things that are in & out of our visual experience
3) Vision operates by representing the world in the mind or the brain
If we assume all 3 we have to explain how all the neural processing in all the
parallel pathways in human visual system results in rich, definite,
representation-based conscious experience
- The basic principle is simple. If you believe that some visual
representations in the brain are conscious and others are not, then you
should be able to take examples of each and study them in detail until you
discover the difference
Filling in the gaps:
William James:
When we look around we don’t and can’t take in everything at once & yet we are
unaware of any gaps.
Why don't we notice the gaps?
- The brain fills in the missing parts
- There’s no need to fill anything in because the gaps are just a lack of info
- An absence of info is not the same as information about an absence
Amodal perception/ conceptual filling-in:
Car is conceptually completed but not visually filled in
(We don’t literally ‘see’ the hidden parts of the car, yet the car seems whole)
Blind spot: Where the optic nerve leaves the back of the eye there are no
photoreceptors, creating a blind spot on the retina that subtends about 6
degrees of visual angle, roughly 15 degrees away from the fovea
- A small object can be made to disappear from sight by lining it up
precisely on the blind spot
- If the background is boring grey → then boring grey fills the space where
the object should have been
