Notes towards a
Computational Theory
of Consciousness
William J. Rapaport
Department of Computer Science & Engineering,
Department of Philosophy, Department of Linguistics,
and Center for Cognitive Science
rapaport@cse.buffalo.edu
http://www.cse.buffalo.edu/~rapaport
2 (or 3) Questions for a
Computational Theory of Consciousness
1. Could a computational cognitive agent
“be conscious”?
•
I think so
– But it depends on what’s meant by “conscious”
1.5. If so, how would we build one?
– Answer depends on “psychological” theories
of consciousness
2. How would we know?
•
•
We wouldn’t…
…any more (or less) than we know about humans!
And What about Qualia?
• “What are qualia?”
≈
“What are numbers?”
≈?
“What is the base case of a recursion?”
• Problem of role of qualia in theories of
consciousness
≈
Problem of mathematical structuralism
What Is Consciousness?
• What is ‘consciousness’?
From the OED:
– L. con- together + sci- knowing;
knowing something with others,
knowing in oneself, privy to
– 1601 (Ben Jonson): Attributed to inanimate
things as privy to, sharing in, or witnesses
of human actions or secrets
– 1620: having the witness of one’s own judgment or
feelings, knowing within oneself
– 1651 (Hobbes): knowing, or sharing the knowledge of
anything, together with another
• Not overly helpful
• Perhaps slightly more helpful…?
Kinds of Consciousness
•
Chalmers:
1. “Psychological” consciousness
2. “Phenomenological” consciousness
•
Better:
1. Psychological problems of consciousness
2. Phenomenological problems of consciousness
“Psychological” Consciousness
• Chalmers:
– “awakeness, introspection, reportability,
self-consciousness, attention, voluntary control,
knowledge, awareness”
– The “easy” problems
• I.e., those explainable in principle in
functional / computational or neural terms, viz. …
“Psychological” Consciousness
“# the ability to discriminate, categorize, and react
to environmental stimuli;
# the integration of information by a cognitive system;
# the reportability of mental states;
# the ability of a system to access its own internal states;
# the focus of attention;
# the deliberate control of behavior;
# the difference between wakefulness and sleep.” [etc.]
(Chalmers 1995, “Facing Up to the Problem of Consciousness”)
– I.e., “awareness”
= Block’s “access” consciousness
“Psychological” Consciousness
•
Models:
X “Cartesian theater”
•
a big “no-no” for humans
 “global workspace”
•
•
Baars, Franklin, Dehaene, et al.
Anderson’s ACT-R buffers
 “multiple drafts”, “fame in the brain”
•
Dennett
On “Multiple Drafts”
• “On the critical question of which version of the
novel [Frankenstein] is truest or best, however,
[Charles E.] Robinson [editor of a scholarly
edition of the Frankenstein Notebooks] demurs:
‘These texts of Frankenstein are what we call
fluid texts,’ he says. ‘There is no single edition
we can judge to be the best.’ ”
– Howard, Jennifer (2008), “The Birth of ‘Frankenstein’,” Chronicle of Higher Education
55(11) (7 November): B12-B15; quote on p. B15.
– For “fluid texts”, read “multiple drafts”.
“Psychological” Consciousness
1.5. “Reflexive” consciousness (Block)
– special case of access consciousness
– HOT (Rosenthal)
– self-representational experiences (Kriegel)
• Any of these models:
– global workspace
– HOT
– multiple drafts, …
could be implemented…
– neurally
– computationally
“Phenomenological” Consciousness
• “experience”,
“what it’s like”,
“qualia”
• ?
– yes (Searle, Chalmers, Nagel, McGinn, Block, G.Strawson)
– no (Dennett)…
“Phenomenological” Consciousness
• “ ‘I can explain to you what love is until I
turn blue in the face. I can take two weeks
to explain everything to you….
‘But there is no way I can make you feel it
until you feel it.’ ” (p. 40)
– Schmidle, Nicholas (2008), “Faith & Ecstasy”,
Smithsonian 39(9) (December): 36-47.
• Cf. Jackson’s “Mary” the color-blind color scientist
• Dennett:
– Qualia can’t be described (in language)
–  Don’t have to/can’t explain them
“Phenomenological” Consciousness
• Dennett (cont’d):
–  qualia
•
 only reports of them
– Don’t have to explain why you experience green or pain
• Because you don’t!
– Only have to explain why you say that you do!
– cf.: How would your experience be different
if Earth revolved around Sun? (Wittgenstein)
– What we think are qualia are really just
states of psychological consciousness
“Phenomenological” Consciousness
• Could “phenomenological” consciousness (qualia) be
nothing but neuron firings?
– yes:
• Searle: It’s just biology (like digestion)
• WJR
– It’s biology for humans…
– but it could be implemented otherwise for computers
» (more later)
– no:
• Chalmers:  non-physical, phenomenological properties
• McGinn: It’s an unsolvable mystery (for us)
• Nagel: It can only be experienced…
– yes?:
• G.Strawson:
– Because everything is “experiential”, including neuron firings.
Nagel:
What Is It Like to Be a Bat?
What Is It Like to Be a Bat?
• Cf. “The Boy Who Sees through Sound”
– Discovery Health documentary
– People (14 July 2006)
• http://www.people.com/people/article/0,26334,1212568,00.html
Is “Consciousness” Univocal?
• Maybe there are lots of different kinds of,
or aspects to, consciousness
• Maybe more than one theory is correct
– Block, in Cognition 79 (2001): 217
The Hard Problem (Chalmers)
• Recall the distinction between:
– Psychological concept of mind/consciousness:
• as causal/explanatory basis of behavior
• functional characterization
• what mind does
– Phenomenal concept of mind/consciousness:
• experience, qualia, what it’s like
• how mind feels
The Hard Problem
• The “hard” problem:
–
–
–
–
“the problem of experience”
How are organisms subjects of experience?
Why do we experience sensations as we do?
Why & how does physical processing give rise
to our rich inner life?
(all quotes/paraphrases from Chalmers 1995)
A Brief Look Ahead
• Suggestion:
– Easy problem…
• i.e., the functional characterization
of psychological consciousness
• … is like a recurrence relation
or recursive clause of a recursive definition
or mathematical structuralism
– Hard problem…
• i.e., qualia, or phenomenal consciousness
• … is like the initial conditions
or base case
or objects that “play roles” in mathematical theories
Chalmers’s Zombie Argument
(simplified version)
1. A “zombie” is_def a creature that is
physically & behaviorally indistinguishable from us,
but that has no conscious experiences.
•
•
http://consc.net/zombies.html
http://plato.stanford.edu/entries/zombies/
2. Physicalism is_def the theory that mental states & processes
(logically) supervene on physical S&P
–
3.
4.
5.
6.
I.e., any physical duplicate of me
would also be a psychological duplicate
Physicalism  zombies are not conceivable
But zombies are “conceivable”
 Physicalism is false
 Psychological phenomena (e.g., qualia) are something
over and above physical phenomena
Ways to React to the Zombie Argument
1. That’s right! (Chalmers)
•
So we’d better devise a separate theory of
psychological consciousness
a)
take mental terms as primitive,
not characterizable in physical terms

cf. Newton & gravity
b) + some psychophysical laws
to tie them in with the physical world

mostly 1-1 correspondences
Ways to React to the Zombie Argument
2. There can’t be any zombies
•
Any sufficiently complex cognitive system
(including any duplicates of me)
will have just as much subjective mentality
as I do
a) Dennett: I.e., none
b) Or: Commander Data will really be just as
phenomenally conscious as I am
(and I really am so!) (*)
Ways to React to the Zombie Argument
• (*) How to give a zombie consciousness?
– A calculator has the ability to add
• but it does so unconsciously, zombie-like
– Give Cassie a theory of math cognition
• then she’d be aware of adding
• she’d be conscious of it in both the psychological
sense and in the phenomenal sense
– she’d have the experience of adding
– but what gives her that experience?
» perhaps Rosenthal-like HOT?
Ways to React to the Zombie Argument
3. There can be zombies:
a) There are plenty of unconscious cognitive processes:
•
“People who solved puzzles with insight activated a specific
subset of cortical areas. Although the answer seemed to
appear out of nowhere, the mind was carefully preparing
itself for the breakthrough. …The scientists refer to this as
the "preparatory phrase," since the brain is devoting its
considerable computational power to the problem. The
various sensory areas, like the visual cortex, go silent as the
brain suppresses possible distractions. "The cortex does this
for the same reason we close our eyes when we're trying to
think," Jung-Beeman said. "Focus is all about blocking stuff
out " ” (New Yorker, 28 July 2008, p. 43)
–
–
•
•
All of this is unconscious; so, zombies are possible
but they could become conscious if another part of the brain
were aware of it, or watching it, HOT-like
I.e., “absent” qualia
So why couldn’t all of them be unconscious?
There Can Be Zombies
b) This is the Really Hard Problem:
•
But then why do we experience some of them?
•
Other really hard problems in the vicinity:
– Why do we experience things as we do and not another way?
 cf. inverted qualia
– Why do we experience red as we do (however we do)
and not as the sound of a bell?
 cf. synaesthesia
Qualia
• A “quale” (plural: “qualia”) is:
– a “raw feel”,
– a “phenomenal experience”,
– “what it’s like”
• It’s what you experience when you…
– sense a color,
– or hear a sound,
– or taste, or smell, or touch.
• It’s what Chalmers says needs to be explained
Qualia: The Classic Problem
• Psychological consciousness can be characterized functionally
(i.e., computationally)
– I.e., in terms of causal and logical relations…
• between inputs and internal concepts,
• among internal concepts,
• & between internal concepts and outputs
• Qualia cannot be characterized functionally
– Because of the possibilities of:
• absent qualia
• inverted qualia
•  Qualia are not psychological
– or else:
Psychological consciousness can’t be characterized
functionally
Do Qualia Exist?—Wittgenstein’s Beetle in the Box
•
•
"Suppose everyone had a box with something
in it: we call it a ‘beetle’. No one can look into
anyone else's box, and everyone says he knows
what a beetle is only by looking at his beetle.
— Here it would be quite possible for everyone
to have something different in his box. One
might even imagine such a thing constantly
changing. — But suppose the word ‘beetle’ had
a use in these people's language? — If so it
would not be used as the name of a thing. The
thing in the box has no place in the language
game at all; not even as a something: for the
box might even be empty. No, one can ‘divide
through’ by the thing in the box; it cancels out,
whatever it is."
(Ludwig Wittgenstein, Philosophical
Investigations I, §293)
Qualia
• Are qualia beetles in boxes?
– Dennett: yes!
– Chalmers:
• maybe (?)
• but I do have a beetle in my box
– even if zombies don’t have beetles in theirs!
Are Qualia Beetles in Boxes?
– WJR:
• we do have qualia
– even if we may be misled by them or misremember them
• we are phenomenally conscious
– even if sometimes we may not remember it
» e.g., “blanking out” when driving or daydreaming
The Hard Problem…for me!
• No matter how detailed our theories of psychological
consciousness are,
I do experience qualia
• Castañeda:
– Philosophy must be done in the first person,
for the first person
• What is that which I experience?
What is experience itself?
• If I try to characterize it in terms of other aspects of my
“mental economy”,
it loses its “raw feel” nature
• But if it is “primitive”, how can I understand it?
• Want a theory of qualia that is consistent with
computational theory of consciousness
2 Main Questions about Qualia
1. Why (& how) do we experience anything
rather than nothing?
– the zombie question
– the really hard problem
2. Why are our qualia as they are
& not like something else?
– answer may depend on answer to #1
Why Do We Experience Anything
Rather than Nothing?
• Some plants are sensitive to light,
some to what we would call odors
– I.e., airborne chemicals
• Can they “see” or “smell”?
• Do we see or smell?
– Or are we, too, merely light- & chemical-sensitive?
• Does anything further happen in the brain?
– I.e., qualia?
– Or are qualia just our sensitivity to the light & chemicals?
– Or is there any sensitivity (or sensation) at all?
Why Do We Experience Anything Rather than Nothing?
• Cf. visual quale of seeing a red (traffic) light
with olfactory quale of an odor
• Cf. these with the lack of an olfactory quale:
– We are qualitatively insensitive to many odors
• We are certainly less sensitive than a dog
– Yet ly these odors do influence our behavior
• “blind smell”; cf. blindsight
– If so, then we are at least partial zombies
– How could that be?
• Why is there such a difference?
• Does the (visual or olfactory) quale do anything?
Why Do We Experience Anything Rather than Nothing?
• Cf. my visual quale of a red light
with my absence of a visual quale
for infrared light
• Suppose infrared light influenced my behavior but I
was not subjectively aware of the IR light
– I could be objectively aware of it:
• via an objective sensing device
• via monitoring my brain
– Would that feel like anything?
• Maybe like an intuition
– That’s a quale, but not necessarily a quale of the IR light
– 2nd-order quale? HOT?
• But probably not like a visual experience of red light
– It wouldn’t be a “deeper” red
Why Do We Experience Anything Rather than Nothing?
•
What’s the difference in my behavior between:
1. my reaction to the quale of red light
2. & my reaction to IR light w/o quale?
•
Case 1:
–
I can voluntarily react (or not react) to the quale of red light

doesn’t run afoul of problem of free will:
 whatever free will turns out to be will work here
•
Case 2:
–
I have no choice

especially if there is not even an intuition
Why Do We Experience Anything Rather than Nothing?
• So we can be partial zombies
– but not complete zombies
– because:
• a complete zombie would have no free will
• but we do
– If the complete zombie had free will,
it would then also have to have some
HOT/access/awareness of the impingement of
the external object(s)…
• chemicals for odor, photons for vision, etc.
…on its sensory apparatus
Why Do We Experience Anything Rather than Nothing?
• Knowing that the external object has so
impinged…
• being aware of its impingement
…from the 1st-person POV…
• i.e., subjective awareness
• not objective awareness
…is the experience of a quale
• but ly  “inverted” qualia
– i.e., what the quale feels like may  physical implementation
Why Are Some Stimuli Experienced as
Colors & Others as Sounds?
• ◊ly because of different sources?
– photons
– sound waves
– chemicals in air
• But could be all felt on a common spectrum
rather than by orthogonal experiences
– ◊ly they are: synaesthesia?
• Why are some things experienced at all,
& some things differently, but others not at all?
– ◊ly because of evolutionary usefulness
• voluntary ability to perform the “4 Fs”
• odors are not useful to us, but are to dogs
Qualia
• Chalmers:
– A mental state or process (MSP)
can be characterized functionally
•
•
•
•
“external” to the mental state or process
“behavioral”
in terms of the MSP’s I/O relations to other MSPs
its “role in the cognitive economy”
– A conscious MSP can also be characterized by
“what it’s like”—its quale
•
•
•
•
“internal”
“phenomenal”
by definition: without functional role
like Wittgenstein’s beetle in the box
Qualia
• Cf. the monetary economy:
– A dollar has the value it has
because of the role it plays
in the world monetary economy
– Does it have an intrinsic value? (a quale?)
• Dennett:
– Does a dollar have “something logically independent of its
functionalistic exchange powers”?
– no: there is no economic theory of such intrinsic value
• WJR:
– at best, $’s intrinsic value is…its role in the world economy.
– might play several roles at once
» cf. Hofstadter on value of Polish zloty
• Maybe: the value of the paper it’s printed on?
– But that value is a function of the world monetary economy!
Qualia
• Cf. axiom systems & intended interpretations:
– Can characterize the natural numbers only as:
• any sequence that satisfies Peano’s axioms
– But an  of sequences do that
– There’s no way to pick out “the” natural numbers
• trying to do that is like trying to characterize qualia
• “Arithmetic is, in this sense, all there is to number:
there is no saying absolutely what the numbers are;
there is only arithmetic”
– Quine 1969: 45
– I.e., numbers : qualia = arithmetic : cog. economy
• Maybe: a cog. agent’s internal mental representation
of numbers corresponds to the qualia?
Qualia
• Benacerraf 1965: “What Numbers Could Not Be”
– 3 is neither { Ø, {Ø}, {Ø,{Ø}} } nor {{{Ø}}}
(& it can’t be both);
– each has properties & relations that the other lacks
and that are irrelevant to numbers, e.g.:
• on both theories, numbers have set-theoretic cardinality
– on one theory, |3| = 3; on the other, |3| = 1;
• on one theory, 1  3; on the other, 1  3
• none of these are true of the natural number 3
– “Any object can play the role of 3”
– “Arithmetic is…the science that elaborates the abstract structure
that all progressions have in common….It is not…concerned with
particular objects—the numbers. The search for which
independently identifiable particular objects the numbers really
are…is…misguided….”
Qualia
• What is a graph?
– =def a structure consisting of:
• a set V of vertices
• & a set E of edges,
• with certain relationships among the members of V & E
– But what is a vertex? what is an edge?
• anything that satisfies the relationships among the members of V & E
– So, a telephone network really is a graph,
because we can take phones to be vertices
& phone connections to be edges
• It’s not merely that a phone network can be modeled
as (or “by”) a graph
• It really is one!
Qualia
• Logically speaking, vertices & edges are
(types of) variables that can take as values
certain phones & connections
– such talk of variables is just talk of roles that
can be played by certain (usually physical)
objects
– the objects implement those roles
(i.e., those abstractions)
Qualia
• Veblen (on his axiomatization of geometry):
– “The terms ‘point’ and ‘order’…differ from the other
terms of geometry in that they are undefined.” (p. 344)
– Because they are undefined,
we are not told what they are
– Therefore, they can be (implemented by)
anything that can play their roles
• Cf. Hilbert on geometry:
– "One must be able to say at all times—instead of points,
lines, and planes—tables, chairs, and beer mugs.”
Qualia
• But Veblen:
– “there is essentially only one class of which
the…axioms are valid” (346)
• I.e., one class “up to isomorphism”
– “In more exact language, any two classes K and
K of objects that satisfy the…axioms are
capable of a one-to-one correspondence”
between them
• i.e., they are isomorphic
Qualia
• Hilbert would agree
• But, in terms of qualia:
– a set of points and lines
(as Euclid thought of them)
that satisfy the axioms…
– …& a set of tables and chairs that satisfy
the axioms…
– …are like a spectrum and an inverted spectrum
Qualia
• White 1974, “What Numbers Are”
– allegedly rebuts Benacerraf
– but really consistent with it
• focuses on the role-filler rather than the role
• a certain set “is a 3 in a certain series”
– I.e., it plays the role of a three
– just as Richard Burton played the role of Hamlet in the
celebrated 1964 production
– “There are indeed numbers, and there are plenty
of them”
• Yes: and there are plenty of different qualia, too
– cf. inverted spectrum
Qualia
• Cf. Rapaport 1999 on implementation as
semantic interpretation:
– The number 3 is anything that implements the
3rd item in a sequence that satisfies the
abstraction described by Peano’s axioms.
– So, is a quale of a MSP anything that
implements it?
• where “it” is characterized functionally,
i.e., in terms of the cognitive economy?
Qualia
•
Gert, “What Colors Could Not Be”, JPhil 2008:
–
–
2 ways to answer “What is X?”
Better: 2 ways to interpret “X is Y”:
1. like “3 = { Ø, {Ø}, {Ø,{Ø}} }”
2. like “water = H2O”
• (1) is part of the answer given in terms of a relational
theory describing what any candidate for X must satisfy,
by giving the “script” for any actor playing the role of X
• (2) gives a particular thing that plays the role
Qualia
• But if there is a functional characterization of water…
– e.g., Chalmers’s “watery stuff”
– or my view of the narrow meaning of “water”
• …then H2O is just one “actor” that can play the role
– and Twin Earth’s XYZ is another
• It’s not that Hamlet is Richard Burton
– rather, Burton is one among many who have played the role
– in a particular production, Hamlet = Burton
Qualia
• Alternatively, compare:
– {{{}}} is (or: is a; or: plays the role of) 3
– Burton is (or: plays the role of) Hamlet
– 3 = S(2)
• which is a functional/structural definition
Mathematical Structuralism & Qualia
• The structural view of math doesn’t
{require / allow} us to specify what 3 is
– Only defines it in terms of its role
• Still:
– When I do arithmetic, I implement 3 somehow
• e.g., as {{{}}}
• or as “3” (most likely!)
• or as my internal mental numeron
Mathematical Structuralism & Qualia
• The functional view of cognition doesn’t
{require / allow} us to specify what qualia are
– Only defines them in terms of their role
• Still:
– They {have to / can} be implemented
– and thus I do experience red in a certain way
Qualia
• Block in Cognition 79(2001):203f
– Functionalism “identifies consciousness with a role”
• just like numbers
– Physicalism “identifies consciousness with a physical
or biological property that fills or implements or
realizes that role in humans”
• just like water = H2O
– “The big question…: How do you know that it is
broadcasting in the global workspace that makes a
representation conscious as opposed to something about
the human biological realization of that broadcasting
that makes it conscious?”
• My answer:
– You don’t!
– Hence the possibility of absent qualia (i.e., zombies).
Qualia
• Dehaene on physicalism (Cognition 79(2001):30):
– qualia might be “biological properties” of
consciousness’s “workspace”
– “each workspace state is ‘highly differentiated’ and of
‘high complexity’….thus the flux of neuronal
workspace states associated with a perceptual
experience is vastly beyond accurate verbal description
or LTM storage….Although the major organization of
this repertoire is shared by all members of the species,
its details result from a developmental process of
epigenesis & are  specific to each individual. Thus,
the contents of perceptual awareness are complex,
dynamic, multi-faceted neural states that cannot be
memorized or transmitted to others in their entirety.”
• This could account for inverted, if not absent, qualia
Qualia
• If MSPs are physically implemented,
then qualia are part of the big picture, after all
– they are values of variables
– those variables are part of the mental
(functional, computational) theory
– their values are part of the physical implementation of
that theory
• a side effect
• an implementation detail
• qualia-variables w/o values are “absent qualia”
– such MSPs would be unconscious
• qualia-variables with different values are “inverted qualia”
Qualia
• Consider a recurrence relation,
or recursively defined function:
– f(0)=q ; f(n+1)=g(f(n))
– the recursion is like the functional theory of consciousness
• Morbini & Schubert: It’s like access consciousness
– the base case is like the quale
• Morbini & Schubert (sort of): It’s like phenomenal consciousness
– if h(0) = r  q & h(n+1)=g(h(n)),
then we have 2 distinct functions with the same “functional”
theory but different “qualia”
• the recursion without the base case is like absent qualia.
– The base case is a particular implementation of the recurrence.
– OR: ◊ly g is what’s like the quale?
• models/implementations of Peano’s axioms can differ in what they take 0
to be (base case) as well as in what they take S to be (i.e., what “g” is).
Qualia
• The principal contrast is between:
– pattern (or function)
– thing (or matter, or shape)
• Hofstadter, Ton Beau de Marot: 307f
• Consider a semantic network representing a functional
characterization of the mind
– Dennett: that’s all that’s needed
– Chalmers: the nodes need identifiers
• identification independent of their connections
• if they do (if they are “filled in”),
then what they are filled in with are qualia
and if yours are filled with something different from mine,
then we have “inverted” qualia
else we have absent qualia
• qualia are dependent on the implementing medium M
– & can be absent or can vary with varying M
Qualia
• Could qualia be nothing but neuron firings?
– ◊ly:
• our phenomenological / qualitative experience
is just
our first-person acquaintance with the neuron firings
• i.e., it is just the way those neuron firings feel
• & this might depend on the implementation
Does It Matter
(for a Computational Theory)?
• When I look at a red box, it seems and looks red
• If you look at it,
could you really see it differently?
• We both can describe it in the same way
& react to it in the same way.
• We both can look at a painting
& discuss its colors, shapes, and emotional significance,
& agree (or agree to disagree) about its beauty
• How could that be if we are having very different
experiences?
Does It Matter?
• Simplest explanation:
– We are having the same or very similar experiences!
– Cf.: simplest explanation of why we see the world as we do:
• The world is as we see it…
• …modulo limitations of our sensory apparatus
– a bat or color-blind dog would see things very differently
– but I wouldn’t expect to be able to sympathize with its aesthetic judgments
as I do with yours
» cf.: “Winston’s problem” (Rapaport 2003, on negotiation)
& Wittgenstein: If a lion could talk, we wouldn’t understand it
» cf.: Dennett: if a lion could talk, not only would we understand it,
but other lions wouldn’t!
Does It Matter?
• Computers can be conscious
– either for Chalmers’s reasons
– or for Dennett’s
• But computers might not have to be conscious
in the way that humans are.
• Whether they are cannot be known (by us)
– from 3rd-person POV, we can’t know another’s qualia
• we can only know our own, from the 1st-person POV
– but there’s no good reason to think others are zombies
• If it cannot be known, then:
there’s no moral reason to treat even possible zombies
(who are behaviorally indistinguishable from us)
any differently from us