PSYchalmers1995

Lecturer's Précis - Chalmers (1995)

"The Puzzle of Conscious Experience"

Copyright Notice: This material was written and published in Wales by Derek J. Smith (Chartered Engineer). It forms part of a multifile e-learning resource, and subject only to acknowledging Derek J. Smith's rights under international copyright law to be identified as author may be freely downloaded and printed off in single complete copies solely for the purposes of private study and/or review. Commercial exploitation rights are reserved. The remote hyperlinks have been selected for the academic appropriacy of their contents; they were free of offensive and litigious content when selected, and will be periodically checked to have remained so. Copyright © 2004, Derek J. Smith (Chartered Engineer).

First published 12:30 BST 23rd September 2004

1 - Introduction

"The Puzzle of Conscious Experience" is rightly famous (a) for being the paper which introduced the term "the hard problem" into the lexicon of psychological enquiry, and (b) for helping to elevate consciousness studies to the status of objective science. It was written by the philosopher-psychologist David J. Chalmers [homepage], then with the Department of Philosophy at the University of California, Santa Cruz, and now at the Australian National University.

Chalmers began by stating what was for him the central problem: "Conscious experience," he pointed out, "is at once the most familiar thing in the world and the most mysterious" (p62). But although we know about it "directly" (that is to say, because consciousness is part of the process of knowing itself), we cannot on this occasion separate out the object to be studied. We are in there with it. The problem is, therefore, one of aspect - of where you are standing when you collect your data. If you are investigating the brain and wish to measure one or other of its physical dimensions or physiological variables, then you have all sorts of highly objective probes and recording devices available to you. This is consciousness from an "objective viewpoint"; you get a lot of data about the underlying machinery but those data do not tell you a lot about the phenomenon itself. You need instead to try to get to grips with consciousness from the "subjective aspect", and that, as it happens, is far from straightforward. For example, you may well be conscious of the page of print in front of you, Chalmers argues, but this consciousness is made up of many different types of experience, from the imagery re-awakened by the print, to the thoughts and emotions thereby evoked, and there are few physical variables then available to comment on the "binding" which holds it all together.

Not surprisingly, this conceptual ambiguity has resulted in different researchers using the word "consciousness" in different ways, so Chalmers concludes his introductory comments by summarising the issues for us .....

"..... we first have to separate the problems that are often clustered together under the name. For this purpose, I find it useful to distinguish between the 'easy problems' and the 'hard problem' of consciousness. The easy problems are by no means trivial - they are actually as challenging as most in psychology and biology - but it is with the hard problem that the central mystery lies. The easy problems of consciousness include the following: How can the human subject discriminate sensory stimuli and react to them appropriately? How does the brain integrate information from many different sources and use this information to control behaviour? How is it that subjects can verbalise their internal states? Although all these questions are associated with consciousness, they all concern the objective mechanisms of the cognitive system. Consequently, we have every reason to expect that continued work in cognitive psychology and neuroscience will answer them. The hard problem, in contrast, is the question of how physical processes in the brain give rise to subjective experience. This puzzle involves the inner aspect of thought and perception: the way things feel for the subject. When we see, for example, we experience visual sensations, such as that of vivid blue. Or think of the ineffable sound of a distant oboe, the agony of an intense pain, the sparkle of happiness, or the meditative quality of a moment lost in thought. All are part of what I am calling consciousness. It is these phenomena that pose the real mystery of the mind." (pp62-63; bold emphasis added.)

Note the clear statement of the hard problem in the above, which Chalmers then supports with the following thought experiment (itself from Jackson, 1982) .....

Exercise 1 - "Mary's Room" - The Case of the Isolated Neuroscientist

1 Imagine Mary, the 23rd century's leading expert on the neuroscience of colour vision. Imagine, too, that Mary (for the sake of the present argument) has lived all her life in a black-and-white room.

2 Mary knows everything there is to know about how colour naming as a brain-mediated perceptuo-motor task varies with different inputs from the spectrum of visible light. She is therefore perfectly placed to explain how a red wavelength, say, is correctly identified, even though she has never experienced that colour herself.

3 Chalmers concludes "that there are facts about conscious experience that cannot be deduced from physical facts about the functioning of the brain" (p64.)

4 Can you see any flaws in this argument?

NB: Brentano (1874/1995, p38) posed a similar problem, when he spoke of "a person who was born blind and another who was born without the sense of smell trying to explain to one another the colour and the scent of a violet".

2 - The Explanatory Gap

Chalmers then goes on to consider the gulf of explanation which exists between those who view consciousness (or, indeed, any complex phenomenon) as a collection of relatively easy-to-understand parts, and those who view it as an irreducible system. Typical of the former account - known as the "reductionist" position - is the philosopher Daniel C. Dennett, who likes to sketch out how individually simple brain processes can come together to produce "a coherent response to a perceived event" (p64). But in fact Dennett's parts have never yet demonstrably produced the desired whole, because "like other reductionist theories, Dennett's is a theory of the easy problems" (p64). The hard problem, on the other hand, "goes beyond problems about how functions are performed", and asks why that performance has to be accompanied by conscious experience in the first place. Chalmers does not deny that consciousness arises from the brain, but complains only that "it is the link itself that perplexes" (p64). The point is that even if a technically advanced theory [Chalmers mentions Hameroff and Penrose's "quantum-physical" theory of consciousness] could one day explain at the reductionist level how the brain makes decisions or solves problems, it would still be "silent about how these processes might give rise to conscious experience" (p64).

Chalmers then adopts the notion of "the explanatory gap", as originally put forward by Ohio State University's Joseph Levine .....

Key Concept - The Explanatory Gap: The explanatory gap is the popular name for the difficulties scientists have in explaining how wholes are so often greater than the sums of their parts. The term was coined by Levine (1983) to encapsulate any theoretical confrontation between a "reductionist" and a "holist" description of a complex phenomenon. <<REVIEWER'S NOTE: Our own views on the explanatory gap in consciousness studies were set down in Smith (1998b), where we drew the analogy with the world of computer programming. All computer programs are written in the first instance in what is known as "source code", and then "compiled" by the appropriate "compiler" [tutorial] into "object code" (a.k.a. "machine code"). The first type of code is meaningful to the programmer, whilst the other makes perfect and immediate sense only to the logic circuits at the heart of the host computer's central processing unit [if we listen to it executing, all we hear is crackle, just like neurons discharging]. There are in fact very precise rules relating object code to source code, but few computing practitioners need to know them - programmers write source code, electronics engineers see to it that the resulting object code gets safely processed, and only compiler writers need to know how the two fit together. The essence of the explanatory gap in consciousness studies is thus tantamount to a "compiler gap", that is to say, we can see the object code - the physiology - at work, but we have yet to unravel the logic behind it. We need a compiler writer's view of cognition. The philosopher Leibnitz also suffered from the explanatory gap. He liked to consider the brain magnified up so that interested investigators could take a tour inside it, like walking through a mill. But all you would ever find, he argued, would be components - never anything to explain the higher order purpose of the structure as a whole. He, too, would have understood a lot more if he had taken his tour accompanied by the mill's designer.>>

3 - Another Thought Experiment

Chalmers then treats us to a second thought experiment, which we have rephrased as the following exercise .....

Exercise 2 - "Dancing Qualia in a Synthetic Brain"

1 Imagine that some clever soul has built an electronic computer so that it exactly mimics the brain in terms of its functional elements and their interconnections. The question at issue would then be whether that machine would ever be "conscious in the same way that [we] are?" (p68). The working hypothesis is that it would not be.

2 Now imagine that you have volunteered to have every biological unit in your visual cortex replaced with an electronic double, one by one, while both you and the research team watch very carefully for any visual or other impairments which might result.

3 If we accept the working hypothesis, it follows that sooner or later one of the chip-for-neuron exchanges will turn out to be critical, and "the resulting brain, with an artificial visual cortex, will have a different conscious experience from the original" (p68). It might make you see purple, for example, when previously you had been seeing red.

4 If you then arranged for your real visual cortex and your machine visual cortex to be switched in and out of service at will, you would be able to flip this switch and have your experience change - "dance" - between the two states, seeing red when your real visual cortex was operating, and purple when your artificial visual cortex took over.

5 Since this state of affairs is potentially reducing to the absurd, there is a case for rejecting the working hypothesis, and suspecting instead that machines can be conscious in the same way we are after all.

6 Can you see any flaws in this argument?

4 - The Concept of Information

At this juncture, Chalmers invites his readers to consider what the purpose of a theory of consciousness should actually be. Its "ultimate goal", he suggests, should be to set down "a simple and elegant set of fundamental laws, analogous to the fundamental laws of physics" (p67). No one yet knows what these are, he argues, but his specific suggestion is "that the primary psychophysical laws may centrally involve the concept of information" (p67).

ASIDE: Chalmers is here using the term information in its technical sense, as popularised by MIT's Claude Shannon in the late 1940s. Readers unfamiliar with the history and technicalities may care to consult our e-paper on "The Relevance of Shannonian Communication Theory to Biological Communication".

Chalmers talks, for example, of a relationship between the "information states embedded in conscious experience" and those within the underlying physical processes. Thus .....

"The three-dimensional encoding of colour spaces, for example, suggests that the information state in a colour experience corresponds directly to an information state in the brain. We might even regard the two states as distinct aspects of a single information state, which is simultaneously embodied in both physical processing and conscious experience. A natural hypothesis ensues. Perhaps information, or at least some information, has two basic aspects: a physical one and an experiential one. This hypothesis has the status of a fundamental principle that might underlie the relation between physical processes and experience. Wherever we find conscious experience, it exists as one aspect of an information state, the other aspect of which is embedded in a physical process in the brain." (p67.)

He then closes with one of the questions which arises from the information hypothesis. This is the issue of the simple household thermostat. Thermostats, Chalmers notes, are in their own humble way information processing systems, so are they conscious? You can answer "no", because you believe that a conscious system has to have a certain minimum threshold of complexity before consciousness can be supported, or you can answer "yes" because you are willing to abandon that threshold .....

"[We might] allow that all information has an experiential aspect - where there is complex information processing, there is complex experience, and where there is simple information processing, there is simple experience. If this is so, then even a thermostat might have experiences, although there would certainly be no accompanying emotions or thoughts. This seems odd at first, but if experience is truly fundamental, we might expect it to be widespread." (p68.)

5 - Evaluation

This paper is important on several counts. Firstly, it did much to promote the scientific study of consciousness, after that topic had been shunned for a century by the behaviourists precisely on the grounds that it was inherently unscientific. Secondly, it placed philosophers front and centre within cognitive science, creating for the first time in history a single integrated approach. And thirdly, it places the concept of information directly in the explanatory gap and shows us how to generate empirically testable hypotheses from the resulting theory. Here is Chalmers' key argument, in revision point format .....

The author distinguishes between the easy problems of consciousness and the hard problem.

The easy problems include matters of physiology and objectively quantifiable neural performance.

The hard problem is the question of how physical processes in the brain give rise to subjective experience. This is arguably philosophy's most important instance of the "explanatory gap", the theoretical gulf between the physical and the psychological explanations of the mind.

The secret of consciousness may ultimately be found to have something to do with the flow of information through the brain. A "natural hypothesis" then suggests itself, namely that information has both a physical and experiential aspect.

There are only two possibilities for conscious mechanisms, one in which a certain minimum amount of systems complexity is needed for a given mechanism to be described as conscious, and the other in which there is no such minimum. However, in accepting the latter option you would then have to permit even rudimentary electric circuits (such as thermostats) to be credited with a primitive form of consciousness.

6 - References

See the Master References List

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