Counterfactual computational vehicles of consciousness

1. Counterfactual computational vehicles of consciousness Ron Chrisley COGS/Dept. of Informatics University of Sussex Toward a Science of Consciousness, Tucson April 7th 2006

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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!)

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

10. Non-branching FSA (Diagrams from Bishop 2002)

11. 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?

12. 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

13. 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…

14. 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 robot’s phenomenal experience" Me: • Not convinced this is a problem • But agree to rule it out for the sake of argument

15. 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."

16. 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!

17. 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 R1n+1 that gives the former a counterfactual property the latter lacks

18. 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

19. 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

20. Segue…

21. "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)

22. 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

23. 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)

24. 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)"

25. 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

26. 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

27. 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

28. 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

29. 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?

30. 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@sussex.ac.uk BICS

31. Thank you! • Thanks to Mark Bishop and Rob Clowes for helpful discussions