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Summaries and reviews of books and papers on mainstream consciousness theories

Consciousness: Philosophical, Psychological and Neural Theories

David Rose, Oxford University Press

INTRODUCTION: This volume provides a good summary of mainstream theories of consciousness. The author admits on a number of occasions that these do not really explain qualia, but at the same time he does not seem willing to look beyond conventional theories. His treatment of quantum consciousness and other 'fundamental theories' is dismissively short, and fails to give an accurate impression of these concepts, or pay more than lip service to the relevance of any levels smaller than the neuron. The author's own idea is that consciousness can somehow be generated from adding together many units at a low level of brain activity, but without allowing the possibility that the study of such levels might discover the existence of processes or forces not immediately understandable on the larger scale. He insists that this is how reductionist science is done, although scientific history would suggest that much of the success of reductionism has come from it allowing the discovery of previously unknown processes and forces at more fundamental levels.

Functionalism is seen as the dominant theory in modern consciousness studies. The theory, which was first propounded in the 1970s, is sometime seen as a successor to the now largely discredited concepts of behaviourism that dominated thinking during much of the 20^th century. Like behaviourism, functionalism emphasises the output or behaviour that results from brain activity. In contrast to behaviourism, mental states are included in functionalism. The system is based on parts or modules of a complex system communicating with one another. The language of communication between the brain modules is sometimes referred to as 'mentalese'. Within this system 'representation' means information that represents things in the outside world, and has intentionality, in the sense of being about something, i.e. about an external object or bodily sensation. These representations can be combined to follow through an argument, or create a representation of something that does not exist in the external world.

The rules for such processing can be applied regardless of the particular mental symbols involved. Therefore, the physical matter in which the processing is instantiated is irrelevant to the system. Functionalism is the direct opposite of identity theory, which insists that brain states are exactly the same as mental states. For functionalism, the physical brain does not matter, except in so far as it allows the operation of rules, but these rules could equally well be implemented on some other structure. Thus the rule system that operates in the human brain could in principle operate in a silicon computer or in some other device, and would produce the same effect regardless of the actual physical basis. Connectionism, a theory that emerged in the late 20^th century provides a limited critique of functionalism. It proposed the idea of neural nets, in which concepts or representations are held as particular sets of neurons rather than the arbitrary symbols employed by functionalism. Connectionism criticised classical functionalism for having no general rule by which neurons could be governed.

It should be noted that functionalism makes what might be regarded as an ambitious assumption about neuroscience, given the rather tentative tone often adopted by neuroscience papers. Functionalism is dependent on the state of neuroscientific knowledge not changing too much from what it is at present. Any discovery that showed the brain processes could not be replicated by a computer, or that the specific nature of the brain's biology played some part in its processing would destroy the theory.

The existence of qualia has proved to be a challenge for functionalism. Qualia (single, quale) are the basic subjective experience of the world. The colour red has been the traditional example, but more complex experience such as seeing grandmother's red leather armchair can also be regarded as qualia. The problem for functionalism is that the rule-based symbol manipulation of the brain as described by this theory does not require subjective experience, and yet most people agree that qualia exist.

In chapter 4, the author makes the perhaps surprising claim that philosophy has progressed a lot since the early days of neuroscience and that modern philosophical developments relate better to the issues involved in consciousness studies. It is at this point that the author proposes the theory of 'homuncular functionalism'. The author's strategy is to break the operation of the brain down into smaller and smaller modules. At the first stage, the brain is divided into modules for vision, hearing etc. At the next stage, vision, for example, is broken down into modules for colour, motion, distance, direction etc. This sub-division into smaller and smaller modules can probably be repeated several times. Eventually, we are looking at small groups of neurons performing very simple sub-functions. The author's point in digging down to this level is that it is easy to comprehend these simple functions as physical processes. At this low level, it can in fact seem that something that is a part of a mental state is just a physical signal. Interaction between such low-level signals gives rise to activity at the next higher level. The author thinks that the problem of consciousness can be resolved in some way by building up from these small overtly physical levels. The expressions mental and conscious are slightly interchanged here, since non-conscious brain processing is reasonably viewed as a perfectly normal physical process. But the author's argument does not say whether consciousness is present at the neuron level, or is generated from it, and if so what it is that's causing this property to arise. He claims that this is the method of science, because of the success of reductionist science in breaking things down to the smallest possible level in order to understand how they work. He also argues that theories that look for an 'Answer' to the consciousness problem will fail, because they do not work up from this reductionist level. In this, he seems to have devised a narrowly restrictive rule system by which any theory that operates at more than one level gets penalty points for this reason. However, it is arguable that the author has not really comprehended the reductionist scientific method. It seems often that breaking things down to this level allows scientists to understand rules that apply at all levels. Thus a reductionist approach to matter gave rise to an understanding of electromagnetism as a force that bound matter together at all scales. The understanding of how matter was bound together did not arise from observing that fundamental particles had no features that were not generally obvious in large objects, but from the exact opposite, of determining the nature of a force as a result of reductionist examination. P. Ironically, another problem of this book is that it is not truly reductionist. Although it pays lip service to the idea of examining the quantum level and the interior of the neuron, in practise it sticks with the century-old convention that the neuron is the lowest level and fundamental unit. For practical purposes, the book seems to view the neuron as a simple switch or black box. Given the importance (arguably exaggerated) attached to levels here, it seems strange that this supposedly reductionist theory takes off from a mid-level structure.

The book does touch on the idea of emergent properties, with consciousness as a possible emergent property of the brain. It is not properly discussed, but fairly apparent, that any emergence is rather arbitrarily assumed to be from neurons rather than from any other level. The classic example of an emergent property is that liquidity is an emergent property of water. However, the comparison with the brain and consciousness is not very helpful. The idea of liquidity as an emergent property of water is only a useful scientific observation, because we understand how the electrical dipoles on water molecules bind the substance together, according to the principles of the electromagnetic force. What is needed in the author's theory is some corresponding principle or force by which small brain units act together to produce the property of consciousness. No suggestions are forthcoming as to what would produce this emergent property in the brain. In general, this book is rather science- light, tending to propound ambitious abstract theories, but having relatively little to say about how these might function physically.

The author touches on the concept of consciousness as a fundamental property of the universe. Most theories of quantum consciousness fall into this category. Fundamental property theories are classified as 'elementary property dualism' or 'elemental'. The author seems keen to elide such ideas with panpsychism, which most researchers would view as being outside the scientific paradigm. This is not really an accurate approach. Panpsychism suggests that consciousness, or spirits pervade all parts of the physical universe, so that a tree, a stream or even a stone has some kind of consciousness. Most forms of quantum consciousness theories bear little resemblance to this charming scenario, since in these theories, rather than pervading the universe, consciousness only arises in the very special conditions prevailing in brains.

The treatment of quantum consciousness in this book is characteristic of much of conventional consciousness studies, being both dismissively short but at the same time managing to pack in a good amount of misrepresentation and error. The author correctly states that Niels Bohr, the leading thinker in early quantum theory, proposed that consciousness, in the form of acts of observation, interacted with the physical world at the quantum level. But he then quite wrongly refers to Penrose as an exponent of the Bohr theory, whereas Penrose went to great lengths to explain his criticism of the Bohr orthodoxy. The description of the role of microtubules is more or less correct, but the author misses the real point of the Penrose/Hameroff theory which is that a certain type of wave function collapse accesses the geometry of spacetime, the fundamental level of the universe, from which mathematical understanding and in Hameroff's version subjective consciousness arises. This is Penrose's answer to the hard problem of consciousness. Rather than criticising this answer, the author oddly claims that Penrose has not provided an answer at all.

The author also wants to fault the theory for moving between levels, but Penrose is in fact consistent with the normal reductionist scientific approach of descending to the smallest possible level, in order to understand forces or properties that operate at all levels. The author claims that the theory does not explain intermediate level effects such as loss of consciousness due reduced blood supply to the brain. This is also probably not true as loss of consciousness is related to proteins in hydrophobic pockets that are unlikely to be completely detached from the indirect effects of greater or lesser blood supply. The old chestnut of the existence of microtubules is wheeled out here, the answer to which is that neurons have a much denser cytoskeleton than cells outside the brain. The supposed problem of whether thoughts collapse the wave function or vice versa also misses the point. In this theory, wave function collapse is a quantum process independent of cognition as such, but allowing, in Penrose's version, additional understanding, and in Hameroff's extended version subjective experience.