Plenary speakers

Is It Conscious? A Question of Mechanism

By Igor Aleksander

Neither behavioral cues nor introspective insight into our own consciousness can provide a test for verifying or denying whether an object, which someone claims is conscious, is indeed conscious. I shall argue that a way of going about it is to discover the presence of some crucially necessary characteristics of the inner machinery found in the object under test. These are cellular mechanisms for an inner depiction and depictive memory (e.g. the equivalent of the extrastriate cortex in living organisms); mechanisms for attention both external and internal; mechanisms for running memory forward in planning mode and mechanisms for 'emotional' evaluation of plans. Examples will be given of an exploratory robot that has been built to test the nature and interaction of the above crucial mechanisms. While these can be seen as necessary mechanisms they are by no means sufficient. This takes the discussion to what is the nature of a sufficient set.

 

Recent brain evidence supports the basic Global Workspace

By Bernard J. Baars

Hypothesis: Global activation due to conscious contents.

A number of researchers have recently begun to voice support for Global Workspace theory (Dennett, 2001; Dehaene, 2002). This is because a large set of brain studies now show that conscious contents activate widespread regions of cortex, while matched unconscious events do not. That hypothesis was first developed based on cognitive evidence by Baars (1988, 1998, 2002).

Global Workspace theory suggests that the brain may be viewed, to a first approximation, as a highly distributed society of specialized processors or networks. A global workspace is a central information exchange that can broadcast messages to the entire society of networks, in order to recruit resources relevant to novel problems. The global message corresponds to conscious contents, which should therefore activate a very wide range of unconscious knowledge sources in the brain. In return, conscious contents are themselves constrained by unconscious coalitions of processors known as "contexts." A great deal of evidence exists for such contextual shaping. Goals and intentions may be viewed as hierarchies of contexts.

Franklin and coworkers have built large-scale computational models incorporating Global Workspace theory. They have shown that it can account for many well-known cognitive functions, including classical Working Memory (Baars & Franklin, unpublished). Thus evidence and theory are converging remarkably well. Consciousness may be the driving engine for all cognitive tasks.

 

Functionalism vs Physicalism in Neuroscientific Approaches to Consciousness

By Ned Block

This paper considers the dispute within philosophy between functionalist and physicalist approaches to the mind and how this dispute arises within neuro-scientific approaches to the nature of consciousness. Functionalists identify consciousness with a role whereas physicalists identify consciousness with a realizer of that role. (The Presidency is a role; G.H. W. Bush was its 41st realizer and G. W. Bush is its 43rd realizer.) It may seem that the dispute is empirically intractable since a functional state and a realizer always appear together. The paper argues that there is no good reason to think this dispute is empirically intractable. The relevance of some experimental findings to the dispute are discussed.

 

Cultivating Consciousness: Chimpanzees and the Impact of Enculturation

By Sarah T. Boysen

Attention plays a pivotal role in the information-processing mechanisms which must in part subserve consciousness. Recent definitions of consciousness (e.g., Donald, 2002) suggest that levels of consciousness are likely found among nonhuman species as well as humans. Two decades of studies with nonhuman primates (chimpanzees) at The Ohio State University Chimpanzee Center suggest that the enculturation process, that is, the immersion of chimps in an artifact-laden human culture with long-term, highly-social, stable human relationships, affects the animals' access to attentional resources in dramatic ways. Such changes, in turn, can facilitate acquisition of complex cognitive concepts, encourage emergent skills, and can also override behavioral predispositions which would preclude or diminish the chimpanzees' ability to grasp new concepts or comprehend task demands. The role of such capacities and its potential relationship to emerging consciousness and cognitive abilities in our own species over evolutionary history will be compared.

 

Why the question of animal consciousness might not matter very much

By Peter Carruthers

According to at least some of the higher-order accounts of phenomenal consciousness which have been proposed (e.g. Carruthers, 2000) it is unlikely that many non-human animals undergo phenomenally conscious experiences. It is commonly believed that any such result must have deep and far-reaching implications for our attitudes towards the rest of the animal kingdom. For example, many people assume that phenomenal consciousness is necessary for animals to have moral significance. They assume that, if it were to turn out that non-human animals lack phenomenally conscious pains and disappointments, then sympathy and concern for their sufferings could no longer be appropriate. In addition, many assume that the absence of phenomenal consciousness from the rest of the animal kingdom would mark a radical and theoretically significant divide between ourselves and other animals, with important implications for comparative psychology. I shall argue that these beliefs are mistaken. On the contrary, the most fundamental object of appropriate sympathy is the frustration of purely first-order desire (Carruthers, 1999) – hence desire which is lacking in phenomenal properties, on a higher-order account. And since phenomenal consciousness might be almost epiphenomenal in nature in its functioning within human cognition, its absence in animals may signify only relatively trivial differences in cognitive architecture. (In my view, it signifies only the absence of a higher-order thought faculty, or ToMM.) Our temptation to think otherwise arises partly as a side-effect of imaginative identification with animal experiences, and partly from failure to separate out which aspects of our common-sense psychology carry the main explanatory burden, whether applied to humans or to non-human animals.

References:

Carruthers, P. 1999. Sympathy and subjectivity. Australasian Journal of Philosophy 77, 465-482.
Carruthers, P. 2000. Phenomenal Consciousness: a naturalistic theory. Cambridge University Press.

 

The search for the computational correlates of consciousness

By Axel Cleeremans

Over the past few years numerous proposals have appeared that attempt to characterize consciousness in terms of what could be called its computational correlates: Principles of information processing with which to characterize the differences between conscious and unconscious processing. Proposed computational correlates include architectural specialization (such as the involvement of specific regions of the brain in conscious processing), properties of representations (such as their stability in time or their strength), and properties of specific processes (such as resonance, synchrony, interactivity or competition).

In exactly the same way that one can engage in a search for the neural correlates of consciousness, one can thus search for the computational correlates of consciousness. The most direct way of doing so consists of contrasting models of conscious vs. unconscious information processing.

In this talk I will review these developments and illustrate how computational modeling of specific cognitive processes can be useful in exploring and in formulating putative computational principles through which to capture the differences between implicit, explicit, and automatic cognition.

What can be gained from such approaches to the problem of consciousness is an understanding of the function it plays in information processing. Here, I suggest that the central function of consciousness is to make it possible for cognitive agents to exert flexible, adaptive control over behavior. Learning processes therefore play a central role in shaping conscious experience.

From this perspective, consciousness is best characterized as involving a continuum defined over quality of representation: Graded representational systems that can be adaptively modified by ongoing experience are thus viewed as a central feature of any successful model of the differences between conscious and unconscious cognition.

 

The fantasy of a first-person science of consciousness

By Daniel C. Dennett

Calls for a "first-person"--or "second-person"-- methodology for a science of consciousness have arisen in recent years. On examination, they turn out to be either elaborations of the third-person method that I have called heterophenomenology, or inadvisable relaxations of good experimental practice. Heterophenomenology is designed to take the first-person point of view seriously--as seriously as any properly neutral method of data-gathering could. To attempt to take it more seriously is to endow conscious subjects with mysterious or miraculous powers that could conceivably exist, but should be demonstrated to exist, not presupposed.

 

Two-way pathways in the brain: What are they for?

By Vince Di Lollo

It has been said that conscious awareness of a visual object emerges from activity in many brain regions, but that one central locus is primarily implicated (e.g., Crick & Koch, 1995; Solso, 2000). This view is predicated on the assumption that visual perceptions arise from a sequence of processing stages within the visual system. That sequence is regarded as being mainly feed-forward, with processing advancing from simple to increasingly complex attributes, along brain pathways that converge to a common area in which conscious perceptions occur. This conventional view is disconfirmed by recent advances in neuroscience which implicate reentrant signaling as the predominant form of communication between brain areas.

In agreement with the neuro-anatomical evidence, my colleagues and I hold to a scheme in which conscious perceptions emerge from iterative exchanges between brain regions linked by reentrant pathways. In this scheme, cortical feedback has two main functions: a) to test for specific patterns in the activity at the lower level, and b) to reconfigure the same neurons at the lower level so that they can perform very different operations at different stages of the processing cycle.

Reconfiguration is part of a comprehensive goal-directed process aimed at tuning the visual system to those attributes and characteristics of incoming stimuli that are likely to prove most useful for performing the task at hand. We believe that reconfiguration is a dynamic process that occurs from moment to moment in everyday viewing.

I will illustrate these principles with evidence from behavioral manifestations such as visual masking, and electrophysiological evidence from event-related potentials that provide converging evidence for a reentrant theory of visual perception and conscious awareness.

 

 

Bonobo Beliefs and Desires: An Inference for Non-Human Consciousness

By William Mintz Fields, Sue Savage-Rumbaugh, & Par Segerdahl

Amid the discussions of what is consciousness and how should it be studied, Ape Language Research continues to address, with recursion, whether the communicative abilities of apes is language, whether apes have a true Theory of Mind; and therefore, whether apes undergo phenomenally conscious experiences. While the history of science may be characterized as a retreat from human specialty, most modern scientists embrace the universal laws of biology as limited to blood and bone (Gardner, 1995). The debate over human uniqueness and the degree to which non-human primates share cognitive, emotional and behavioral similarities with humans vigorously continues. Despite the absence of empirical proof, the scientific community, via a form of consensus analysis, largely considers consciousness to be a property of humanness. This report seeks to inform the discussion of animal consciousness through an exploration of the ethical and moral communications of human enculturated great apes. The study is based upon a continuous investigation of a captive society of bonobos, living in Decatur, Georgia. It has been empirically demonstrated that these apes possess the capacity to comprehend spoken English, use symbols to express ideas, produce Oldowan quality rock tools, and to speak certain English words. We present data supporting the ideas that (1) Some of the apes at the Language Research Center make ethical choices based upon moral rules. And (2) Bonobo Kanzi and his sister Panbanisha have the capacity to autobiographically report "beliefs and desires about beliefs and desires" (Dennett 1987) regarding their Pan/Homo cultural world.

 

Testable Hypotheses from the IDA Model of Global Workspace Theory

By Stan Franklin

IDA (Intelligent Distribution Agent) is an intelligent, autonomous software agent developed for, and funded by, the US Navy over the past five years. At the end of each sailor's tour of duty, he or she is assigned to a new billet. The Navy employs some 280 people (detailers) to effect these new assignments. IDA completely automates the role of the human detailer. IDA has been designed, coded, tested, and is operational and approved by the Navy.

Implementing Global Workspace Theory, IDA computationally models a broad swath of human cognition. This includes perception, working memory (WM), long-term memory (LTM), "consciousness", action selection (decision making), constraint satisfaction, deliberation and volition, and negotiation. She conceptually models other cognitive faculties that have not yet been implemented including automization, novel problem solving, and the relationships between various human memory systems.

The IDA Model has produced a long list of hopefully testable hypotheses concerning human cognition and the role consciousness plays. Here are example hypotheses relating to memory:

  1. There is a content-addressable, associative, Transient Episodic Memory (TEM) with a decay time measured in hours or perhaps a day.
  2. The contents of Working Memory (WM) cue the retrieval of local associations from each of TEM and Long-term Associative Memory (LTM).
  3. An attention mechanism selects the next contents of consciousness from the contents present in WM and these two local associations.
  4. The contents of consciousness are stored in TEM.
  5. During sleep the contents of TEM are consolidated into LTM more quickly than during the waking state.
  6. A corollary to 4 and 5: Only consciousness contents are stored in LTM.

This talk will begin with an overview of the IDA Model and continue with a discussion of various hypotheses arising from it. Our primary goal will be to entice listeners to test some of these hypotheses.

 

High resolution EEG brings us another step closer to the NCC?

By Walter J. Freeman

Sensation and perception both require dendritic currents and axonal action potentials of enormous numbers of neurons that are widely distributed in the forebrain. The spatiotemporal neural activity patterns that support sensation differ dramatically from those that support perception. Sensation is mediated by action potentials of feature-detector neurons that are best observed with microelectrodes and best modeled with neural networks. Perception is supported by the formation of large scale patterns of coordinated action potentials from millions of neurons. Perceptual patterns are best modeled as densities in a continuous sheet, and they are best observed using electrode arrays to record the electrical potentials (electroencephalographic waves, EEG) caused by sums of the dendritic currents that control the action potentials.

A two-stage mechanism is proposed by which sensory cortical activity that is stimulus-driven by receptor input induces hemisphere-wide, self-organized patterns of perceptual neural activity within 300-500 ms of stimulus onset. In the 1st stage sensory input destabilizes the primary receiving areas, so that the random microscopic action potentials condense into a wave packet that constitutes an order parameter, like a rain drop that is formed from water vapor.

The 2nd stage occurs as wave packets from all sensory areas are carried by action potentials through the forebrain. The dendritic integration of activity destabilizes much or all of the hemisphere, and a global pattern emerges. Such patterns have been observed in animals by intracranial recording of EEG from multiple areas, and noninvasively in normal humans by multichannel recording of scalp EEG. Observation with common clinical equipment is facilitated by use of dense electrode arrays for high spatial resolution and the Hilbert transform for high temporal resolution. The patterns provide access by every clinic and psychology laboratory to the synchrony used by the brain in high level cognitive functions involving perceptual experience.

 

A Framework for Consciousness

By Christof Koch

In this talk, I will summarize Francis Crick's and mine present approach to the problem of consciousness. This framework proposes a coherent scheme for explaining the neural correlates of (visual) consciousness in terms of competing coalitions of forebrain neurons, based on explicit representations and the columnar properties of cortex. I will discuss the crucial role of feed-back pathways and the role of (pre)frontal cortex in conscious perception.

 

Why visual attention and awareness are different

By Victor A.F. Lamme

Now that the study of consciousness is warmly embraced by cognitive scientists, much confusion seems to arise between the concepts of visual attention and visual awareness. Often, visual awareness is equated to what is in the focus of attention. There are however two sets of arguments to separate attention from awareness: a psychological / theoretical one, and a neurobiological one. By combining these arguments I present definitions of visual attention and awareness that clearly distinguish between the two, yet explain why attention and awareness are so intricately related. Central to this thesis are, at the neural side, the distinction between feed-forward and recurrent processing, and, at the psychological side, the threefold distinction between unconscious processing, phenomenal experience and access awareness.

 

Binocular rivalry and the illusion of monocular vision

By David Leopold

In the psychophysical phenomenon of binocular rivalry, two dissimilar visual patterns presented independently to the two eyes give rise to a wavering percept. Despite constant sensory stimulation, vision during rivalry draws alternately from each eye's stimulus in a sequence of subjective reversals that continues as long as the interocular conflict is present. What is the nature of this phenomenon, and what might be its value in studying conscious visual perception? Many earlier observations suggested that rivalry is fundamentally a problem of binocular vision, and likely due to reciprocal circuitry at or before the primary visual cortex. For example, the relatively unselective suppression of all attributes of a pattern in the non-dominant eye might be explained if, at any point in time, only one eye's information penetrates beyond the earliest cortical processing stages. Such a mechanism might account well for the singleness of vision experienced during rivalry. However a growing body of psychophysical and physiological observations suggests that this simple view of rivalry cannot be correct. For example, neurons throughout the visual cortex are vigorously activated by sensory patterns, even when they are presented to the non-dominant eye (and are thus unperceived). Thus, in trying to understand how perception emerges during rivalry, it is imperative to reconcile the distinct monocular perception with the fact that both eye's patterns are extensively processed in the brain. In my talk, I will consider this problem as one appealing to active mechanisms of perceptual organization well beyond the site of binocular convergence in primary visual cortex. I will argue that a few residual monocular signals in higher visual areas might aide in shaping the percept during rivalry, but according to high-level principles derived from the constraints imposed on our normal binocular vision. I will conclude by discussing the lessons that might be offered by binocular rivalry with regard to the quest for the neural correlates of consciousness.

 

Conscious top-down modulation of some unconscious processes : Automaticity revisited in the light of the Global Workspace hypothesis

By Lionel Naccache

In current theories of human cognition, unconscious processes are often considered as automatic processes that do not require attention and which are impermeable to top-down influences. Recently, however, several studies have reported converging evidence against this view. In particular, I shall describe multiple subliminal priming studies revealing that top-down instructions and attention have a major impact on processing of subliminal masked primes. Taken together, these results require a revision of the psychological concept of automaticity, leading to a fundamental distinction between the source of top-down influences and their effects.

 

What does binocular rivalry teach us about consciousness?

By Alva Noe

Binocular rivalry is an important phenomenon, one that provides insight onto the the nature of perceptual phenomenology and its basis in the brain. But what does it teach us, exactly? In this paper, drawing on joint work with Evan Thompson, I explore this topic with special attention to the question: are there neural correlates of consciousness? I present the enactive/sensorimotor approach to perception and consciousness.

Background reading: (forthcoming papers and other related material are available at: http://people.ucsc.edu/~anoe/)

S. Hurley and A. Noe (forthcoming) Neural plasticity and consciousness. BIOLOGY AND PHILOSOPHY.
A. Noe (forthcoming) ACTION IN PERCEPTION. The MIT Press.
A. Noe and E. Thompson (forthcoming) Are there neural correlates of consciousness? JOURNAL OF CONSCIOUSNESS STUDIES.
J.K. O'Regan and A. Noe (2001) A sensorimotor approach to vision and visual consciousness. BEHAVIORAL AND BRAIN SCIENCES 24 (5): 883-975.

 

Bonobo Beliefs and Desires: An Inference for Non-Human Consciousness

By William Mintz Fields, Sue Savage-Rumbaugh, & Par Segerdahl

Amid the discussions of what is consciousness and how should it be studied, Ape Language Research continues to address, with recursion, whether the communicative abilities of apes is language, whether apes have a true Theory of Mind; and therefore, whether apes undergo phenomenally conscious experiences. While the history of science may be characterized as a retreat from human specialty, most modern scientists embrace the universal laws of biology as limited to blood and bone (Gardner, 1995). The debate over human uniqueness and the degree to which non-human primates share cognitive, emotional and behavioral similarities with humans vigorously continues. Despite the absence of empirical proof, the scientific community, via a form of consensus analysis, largely considers consciousness to be a property of humanness. This report seeks to inform the discussion of animal consciousness through an exploration of the ethical and moral communications of human enculturated great apes. The study is based upon a continuous investigation of a captive society of bonobos, living in Decatur, Georgia. It has been empirically demonstrated that these apes possess the capacity to comprehend spoken English, use symbols to express ideas, produce Oldowan quality rock tools, and to speak certain English words. We present data supporting the ideas that (1) Some of the apes at the Language Research Center make ethical choices based upon moral rules. And (2) Bonobo Kanzi and his sister Panbanisha have the capacity to autobiographically report "beliefs and desires about beliefs and desires" (Dennett 1987) regarding their Pan/Homo cultural world.

 

What kind of virtual machine is capable of human consciousness?

By Aaron Sloman

Most people think that because they experience and talk about consciousness they have a clear understanding of what they mean by the noun "consciousness". This is just one of many forms of self-deception to be expected in a sufficiently rich architecture with reflective capabilities that provide some access to internal states and processes, but which could not possibly have complete self-knowledge. This talk will approach the topic of understanding what a mind is from the standpoint of a philosophical information-engineer designing minds of various kinds.

A key idea is that besides physical machines that manipulate matter and energy there are virtual machines that manipulate information, including control information. A running virtual machine (for instance a running instance of the Java virtual machine) is not just a mathematical abstraction (like the generic Java virtual machine). A running virtual machine includes processes and events that can interact causally with one another, with the underlying physical machine, and with the environment. People rely on the causal powers of such virtual machines when they use the internet, use word processors or spelling checkers, or use aeroplanes with automatic landing systems. So they are not epiphenomenal.

Such a virtual machine may be only very indirectly related to the underlying physical machine and in particular there need not be any simple correlations between virtual machine structures and processes and physical structures and processes. This can explain some of the alleged mystery in the connections between mental entities and processes and brain entities and processes.

We'll see how some designs for sophisticated information-processing virtual machines are likely to produce systems that will discover in themselves the very phenomena that first led philosophers to talk about sensory qualia and other aspects of consciousness. This can serve to introduce a new form of conceptual analysis that builds important bridges between philosophy, psychology, neuroscience, biology, and engineering. For instance, qualia can be accounted for as internally referenced virtual machine entities, which are described using internally developed causally-indexical predicates that are inherently incommunicable between different individuals.

All this depends crucially on the concept of a virtual machine which despite being virtual has causal powers. A draft version of the presentation with some additional notes can be found here: http://www.cs.bham.ac.uk/research/cogaff/talks/#talk23

Papers and talks providing background to the presentation can be found here:

http://www.cs.bham.ac.uk/research/cogaff/
http://www.cs.bham.ac.uk/~axs/misc/talks/

 

Blindsight and Plasticity

By Petra Stoerig

In fields of absolute cortical blindness resulting from destruction or denervation of the primary visual cortex, a variety of non-reflexive visual functions can be demonstrated even though the patients are unaware of the stimuli they respond to. This phenomenon of Blindsight can help us to understand both what neuronal pathways are necessary for conscious vision and what can and cannot be done in its absence. To tackle these two questions, I have tested four patients in 2AFC-tasks including detection of luminance- or color-defined targets, and discrimination of stimuli differing in orientation or in color, giving feedback after each response. The results show that within the up to 14 series of 100 trials given all four patients, albeit to a different extent, mastered luminance detection and orientation discrimination, but only two performed significantly above chance in the other two tasks. In most cases, analysis by series of trials showed that performance improved over time, implying that perceptual learning is possible in the absence of conscious vision. This indicates that Blindsight does not emerge fully-fledged when conscious vision is lost, but that it may need to be learned. Similar conclusions can be drawn from an experiment of object discrimination done with another group of patients. In view of the evidence for learning, it is difficult to assess what functions cannot be learned - and therefore depend on conscious vision – because it is hard to decide when to stop. Evidence from functional magnetic imaging indicates that the strength of residual responses in higher ipsilesional visual cortical areas is also subject to change. Whether, when training is continued longterm, blindsight reaches ceiling, or whether some conscious vision returns once a critical level of responsivity is reached, remains to be seen. (Supported by the Deutsche Forschungsgemeinschaft, SFB 194-A15).

 

Binocular Rivalry and Perceptual Awareness in Human Primary Visual Cortex

By Frank Tong

To understand conscious vision, scientists must elucidate how the brain selects specific visual signals for awareness. During binocular rivalry, different monocular patterns presented to the two eyes compete conscious expression such that only one monocular image is perceived at a time. Controversy surrounds whether binocular rivalry arises from pattern competition in high-level extrastriate areas or early interocular competition in primary visual cortex (V1). I will describe recent fMRI studies showing that awareness-related activity during rivalry is clearly evident in human V1, and appears to be fully resolved in a monocular region of V1 corresponding to the blind-spot representation. We find that fMRI activity in monocular cortex entirely reflects the subject's perception state during rivalry rather than the physical stimulus. Our findings support the proposal that interocular competition mediates binocular rivalry, and further suggest that V1 may have an important role in the selection and maintenance of conscious visual information. The relationship between V1 and awareness for other types of perceptual phenomena will also be discussed.