3 Global Workspace Architecture Parallel UnconsciousSpecialist ProcessesGlobal WorkspaceMultiple parallel specialist processes compete and co-operate for access to a global workspaceIf granted access to the global workspace, the information a process has to offer is broadcast back to the entire set of specialists
4 Conscious vs Non-Conscious Global workspace theory (Baars) hypothesises that the mammalian brain instantiates such an architectureIt also posits an empirical distinction between conscious and non-conscious information processingInformation processing in the parallel specialists is non-consciousOnly information that is broadcast is consciously processed
5 EmbodimentAccording to GWT, only something that instantiates a global workspace architecture is capable of conscious information processingBut this is a necessary not a sufficient conditionI have argued (Shanahan, 2005) that the architecture must direct the actions of a spatially localised body using a sensory apparatus fastened to that bodyThis allows the set of parallel specialists a shared viewpoint, from which they can be indexically directed to the world and fulfil a common remit
6 Empirical EvidenceContrastive analysis compares and contrasts closely matched conscious and unconscious brain processesDehaene, et al. (2001)Imaged subjects being presented with “masked” wordsMasked and visible conditions comparedSuch experiments suggest that conscious information processing recruits widespread brain resources while unconscious processing is more localised
7 Neural Parallelism An animal’s nervous system is massively parallel Masssive parallelism surely underpins human cognitive prowessSo how are the massively parallel computational resources of an animal’s central nervous system harnessed for the benefit of that animal?How can they orchestrate a coherent and flexible response to each novel situation?Nature has solved this problem. How?
8 Serial from Parallel / Unity from Multiplicity The global workspace architecture supplies a possible answerThe global workspace itself exhibits a serial procession of statesYet each state-to-state transition is the result of filtering and integrating the contributions of huge numbers of parallel computationsThe global workspace architecture thereby distils unity out of multiplicity( This is perhaps the essence of consciousness, of what it means to be a singular, unified subject )
10 The Frame Problem (1) The frame problem orginated in classical AI This is tricky, but was more-or-less solved in the mid 1990sOur concern is the wider interpretation given to the frame problem by philosophers, notably Dennett and FodorHow can we formalise the effects of actions in mathematical logic without having to explicitly enumerate all the trivial non-effects?
11 The Frame Problem (2) Fodor’s version: A cognitive process is informationally unencapsulated if it has the potential to draw on information from any domainAnalogical reasoning is the epitome of informational unencapsulationHow do informationally unencapsulated cognitive processes manage to select only the information that is relevant to them without having to explicitly consider everything an agent believes ?
12 Computational “Infeasibility” Fodor claims that informationally unencapsulated cognitive processes are computationally infeasibleFodor believes that this is a fatal blow for cognitive science as we know it because it entails we cannot find a computational explanation of the human mind’s “central systems”“ The totality of one’s epistemic commitments is vastly too large a space to have to search … whatever it is that one is trying to figure out. ”(Fodor, 2000)
13 Fodor’s Modularity of Mind The mind’s peripheral processes are special purpose, do things like parsing and low-level vision, and are computationalThe mind’s central processes are general purpose, do things like analogical reasoning, are informationally unencapsulated, and probably aren’t computational“… it probably isn’t true that [all] cognitive processes are computations. … [so] it’s a mystery, not just a problem, what model of the mind cognitive science ought to try next. ” (Fodor, 2000)
14 GWT and the Frame Problem (1) Both Fodor and Dennett seem to have a strictly serial architecture in mind when they characterise the frame problemPeripheral Processes (Modules)Central ProcessesBDAC“Is A relevant?”“Is B relevant?”“Is C relevant?Yes!”This certainly looks computationally infeasible
15 GWT and the Frame Problem (2) But global workspace architecture offers a parallel alternative (Shanahan & Baars, 2005)Parallel Unconscious SpecialistsGlobal WorkspaceBDAC“Am I relevant?”“Am I relevant?Yes!”In the context of an appropriate parallel architecture, the frame problem looks more manageable
16 Analogical Reasoning (1) Analogical reasoning is informational unencapsulation in its purest formComputational models of analogical reasoning distinguish betweenretrieval – the process of finding a potential analogue in long-term memory for a representation already in working memory – andmapping – the subsequent process of finding correspondences between the two“Analogical reasoning depends precisely upon the transfer of information among cognitive domains previously assumed to be irrelevant ” (Fodor)
17 Analogical Reasoning (2) Retrieval is the locus of the frame problem in analogical reasoningOne of the most psychologically plausible computational models is LISA (Hummel & Holyoak), which mixes serial and parallel computation, and also fits a global workspace architecture very closelyLISAGWTSerial presentation in working memoryActive proposition in WMParallel activation in long-term memoryDistributed propositions in LTMSerial presentation in global workspaceContents of GWBroadcast of GW contentsUnconscious parallel processes
19 The Simulation Hypothesis “Thought is internally simulatedinteraction with the environment” (Cotterill, 1998)Internal simulation is integral to our inner life and facilitates anticipation and planningThree assumptions (Hesslow, 2002)The brain’s motor centres can be active without producing overt actionThe brain’s perceptual apparatus can be active without the presence of external stimuliInternally generated motor activity can elicit internally generated perceptual activity through associative mechanisms
20 Combining a GW with Internal Simulation BroadcastSelection /competitionGWCorticalarea 1area 2area 3It’s possible to combine an internal sensorimotor loop with mechanisms for broadcast and competition, and thereby marry the simulation hypothesis with global workspace theory
21 A Biologically Non-implausible Implementation Column 2Column 1Column 3Global neuronalworkspaceBuilt out of spiking neurons with transmission delaysCortical columns comprise 32 32 fully connected netsWorkspace nodes comprise 16 16 topographically mapped regionsCortical columns trained to associate successively presented pairs of images using STDP
22 Controlling a RobotThe inner sensorimotor loop can be embedded in a larger system and used to control a robotThis results in a form of “cognitively-enhanced” action selectionThe implemented action selection architectureIs based on salience and winner-takes-allImposes a veto at final motor output stageModulates salience as a result of internal simulationReleases veto when salience exceeds a thresholdThe parallelism of the GW architecture enables the inner loop to explore alternatives
23 The “Core Circuit” VC / IT = visual cortex / inferior temporal cortex GW / BGAC1aAC2aAC3aAC1bAC2bAC3bVC / ITAmVC / IT = visual cortex /inferior temporal cortexAC = association cortexGW / BG = globalworkspace / basalgangliaAm = amygdala
24 A Proof-of-Concept Experiment NRMmodelWebotssimulatorMotorCortexCamerainputSaliencepopulationsKheperaAssociationCortexCameraviewReward &punishmentMotor vetoMotoroutputGlobalWorkspace
25 Concluding RemarksCombination of GW architecture and internal simulation is a promising non-classical-AI approach to cognitive roboticsShortcomings of current workUse of biologically non-plausible neuron modelUse of attractor net to model global workspaceDynamically uninteresting robotOngoing and future workNew model of core circuitry (partly achieved)Realistic spiking neuronsBroadcast through resonance and synchronyDynamically complex robot (eg: CRONOS)
26 ReferencesShanahan, M.P. & Baars, B.J. (2005). Applying Global Workspace Theory to the Frame Problem, Cognition 98 (2), 157–176.Shanahan, M.P. (2005). Global Access, Embodiment, and the Conscious Subject, Journal of Consciousness Studies 12 (12), 46–66.Shanahan, M.P. (2006). A Cognitive Architecture that Combines Inner Rehearsal with a Global Workspace, Consciousness and Cognition 15, 433–449.