Counterfactual computational vehicles of consciousness

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Counterfactual computational vehicles of
consciousness

• Ron Chrisley
• COGS/Dept. of Informatics
• University of Sussex

Toward a Science of Consciousness, Tucson April
7th 2006
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Outline

• Bishop's argument against computational
  explanations of consciousness
• My response Acknowledge the counterfactual
  nature of physical states
• Segue Use emphasis on counterfactual properties
  as motivation for a specific form of
  computationalism/representationalism
• Provides a plausible yet non-trivial enactivist
  model of perceptual experience Imagination-Based
  Architecture

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Bishop "Dancing with Pixies"

• Poses a dilemma for computational explanations of
  consciousness
• Horns based on two notions of computation
• Non- or weakly- causal construal of computation
• Strong, counterfactual causal construal of
  computation

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Bishop's dilemma

• Either notion has problems
• Horn 1 Weak causality
• Implies every computation is realised in every
  physical system
• So any claim that a given computation is
  sufficient for consciousness implies panpsychism
• Phenomenal "pixies" everywhere!
• Horn 2 Strong causality
• Violates naturalism by appealing to non-physical
  aspects of a state

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Rejecting the first horn

• Yes, weakly causal construal of computation
  implies panpsychism
• But
• What's wrong with panpsychism anyway?
• Actually, a lot
• Better (cf Chalmers 94, 96 Chrisley 94)
• Weak construal not really a causal construal of
  computation at all
• Thus does not capture what is meant by
  computation

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Embracing the second horn

• Strong, counterfactual causal construal of
  computation
• Identity of a computational state depends not
  only on actual causal relations
• but also on causal effects (output, successor
  state) a state would have had were different
  input received
• Bishop Subject to variants of Chalmers' Fading
  Qualia and Suddenly Disappearing Qualia arguments

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Bishop's thought experiment

• Consider the operation of two robots
• R1 "controlled by a program replicating the
  fine-grained functional organisation of a system
  known to have phenomenal states"
• A particular run of R1 with input I results in an
  actual sequence of behaviours B
• R2 any open physical system that generates B,
  given the same input I

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More on R1 and R2

• For example, R1 might be controlled by an AI
  program that enables it to output classifications
  of objects presented to its cameras
• When given the input of a particular object, this
  results in a particular sequence of output
  classifications B
• "This colour of this triangle is a bit more red
  than the square I just saw"
• While R2 can just have a hard-wired circuit that
  happens to output B (regardless of input!)

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Branching FSA

• We can conceive of R1 and R2 as a finite-state
  automata with branching and non-branching states,
  respectively

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Non-branching FSA
(Diagrams from Bishop 2002)
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The computationalist's view

• Bishop "Hence, although the external behaviour
  of the two systems over the time interval is
  identical viz, B, for a computational theory
  of consciousness, only R1 would experience
  genuine phenomenal states."
• What's wrong with that?

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Transforming R1 into R2

• One by one, delete one of the N state transition
  sequences of R1 that are not actually used in the
  case under consideration, to transform R1 into
  R11, R11 to R12 to R1N
• R1N will be computationally formally identical
  with R2
• So for a computationalist, R1N, like R2, has no
  conscious experience

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R1, R2 another dilemma

• Bishop
• "What happens to the phenomenological experience
  of R1 as it incrementally undergoes the above
  transformation?"
• "Either its experience of phenomenal states must
  gradually fade (Fading Qualia) or it must switch
  abruptly at some point (Suddenly Disappearing
  Qualia)."
• Me
• Not necessarily There might be several, spaced,
  discrete transitions.
• But let that pass

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No SDQ?

• Bishop
• Rule out first horn Suddenly Disappearing
  Qualia
• It would "imply that the removal of one such
  privileged branching state transition instruction
  would result in the complete loss of the robots
  phenomenal experience"
• Me
• Not convinced this is a problem
• But agree to rule it out for the sake of argument

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A general argument?

• Bishop presents an argument not against the
  second horn (Fading Qualia), but against
  computationalism in general
• The computationalist's position implies the
  existence of "a system, whose phenomenal
  experience is contingent upon non-physical
  interactions with sections of its control program
  that are not executed a form of dualism."
• "Hence, if phenomenal states are purely physical
  phenomena, the phenomenal experience of the two
  robot systems, R1 and R2, must be the same."

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Warning sign Too strong

• An indication that Bishop's argument can't be
  right
• It proves too much
• If right, it would imply that there could never
  be a physicalist computational explanation of
  anything
• not even computers!

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Misunderstanding the physical

• Bishop's main mistake claiming that differences
  in counterfactual behaviour do not constitute
  physical differences
• Presumably, it is by virtue of some physical
  difference between a state of R1n and the
  corresponding state of R1n1 that gives the
  former a counterfactual property the latter lacks

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Misunderstanding the physical

• Note that to delete the nth transition, one would
  have to physically alter R1n-1
• So despite Bishop's claim, if R1 and R2 differ in
  their counterfactual formal properties, they must
  differ in their physical properties
• Causal properties (even counterfactual ones)
  supervene on physical properties

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Counterfactuals are key

• So much for Bishop's argument against
  computational accounts of consciousness
• But although Bishop has nothing on
  computationalism in theory, he inspires a
  relevant critique of the form it usually takes
• That is, standard computationalist theories of
  consciousness neglect the importance of
  counterfactual properties

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Segue
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"Actualist" computationalism

• Typically, computationalist (or functionalist)
  theories attempt to map
• A perceptual phenomenal content
• To a computational (functional) state
• By virtue of the latter's actual causal origins
  (and perhaps its actual causal effects)

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The Grand Illusion?

• For example, some argue
• Change blindness data show that only foveal
  information has an effect on our perceptual state
• Thus, our perceptual experience is only of the
  foveated world
• Any appearance that anything else is experienced
  is incorrect

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Being counterfactual

• But a computationalist theory that places
  explicit emphasis on the role of counterfactual
  states can avoid the Grand Illusion result
• E.g. The phenomenological state corresponding to
  a given computational state includes not just
  current foveal input
• But also the foveal input the computational
  system would expect to have if it were to engage
  in certain kinds of movement
• "Imagination-based architecture" (IBA)

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More on IBA

• These expectations can be realized in, e.g., a
  forward model, such as a feed-forward neural
  network
• The model is updated only in response to foveal
  information
• E.g., it learns "If I were to move my eyes back
  there, I would see that (the current foveal
  content)"

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The IBA explanation

• Thus, change blindness can be explained without
  denying peripheral experience
• Consider the system after an element of the scene
  has changed, but before the system foveates on
  that part of the scene
• The expectations of the forward model for what
  would be seen if one were to, say, foveate on
  that area, have not been updated

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No Grand Illusion

• According to IBA, the (outdated) expectation is a
  part of current experience
• Thus no change is detected or experienced
• So our experience is just what it seems

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Elaborations to IBA

• Only a simplistic version of IBA presented here
• Can be elaborated to include change not
  instigated by the system itself
• E.g., expectations of what foveal information one
  would receive if the world were to change in a
  particular way

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More elaborations to IBA

• Weighted contributions to experience
• Current foveal info strongest of all
• Expected foveal after a simple movement a little
  less
• Contribution of expected results of complex
  movements/sequences inversely proportional to
  their complexity

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Open questions for IBA

• E.g., what is the experience at a non-foveated
  part of the visual field if one has different
  expectations for what one would see depending on
  the motor "route" one takes to foveate there?
• Some "average" of the different expectations?
• Winner take all?
• Necker-like shift between top n winners?
• No experience at that part of field at all, as
  coherence (systematicity, agreement) at a time is
  a requirement for perceptual experience?

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Announcements

• For philosophers of Cognitive Science/AI
• My department, Informatics at the University of
  Sussex/COGS is hiring
• Tell your friends/colleagues!
• Those interested in Machine Consciouness
• Conference I am chairing, BICS 2006 in the Greek
  Islands, October, is still accepting submissions
  to the end of April
• Email me about either/both ronc_at_sussex.ac.uk

BICS
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Thank you!

• Thanks to Mark Bishop and Rob Clowes for helpful
  discussions