Dennett, Daniel Clement; Paul Weiner (ill.);
Consciousness Explained
Little, Brown and Co., 1991, 528 pages
ISBN 0316180661, 9780316180665
topics: | philoosphy | cognitive | brain | mind-body | ai | consciousness
Suppose evil scientists removed your brain from your body while you slept, and set it up in a life-support system in a vat. Suppose they then set out to trick you into believing that you were not just a brain in a vat, but still up and about, engaging in a normally embodied round of activities in the real world. This old saw, the brain in the vat, is a favorite thought experiment in the toolkit of many philosophers. It is a modern-day version of Descartes's (1641)1 evil demon, an imagined illusionist bent on tricking Descartes about absolutely everything, including his own existence. But as Descartes observed, even an infinitely powerful evil demon couldn't trick him into thinking he himself existed if he didn't exist: cogito ergo sum, "I think, therefore I am." philosophers have assumed for the sake of argument that however technically difficult the task might be, it is "possible in principle." One should be leery of these possibilities in principle. It is also possible in principle to build a stainless-steel ladder to the moon, and to write out, in alphabetical order, all intelligible English conversations consisting of less than a thousand words. But neither of these are remotely possible in fact and sometimes an impossibility in fact is theoretically more interesting than a possibility in principle, We are — and should be — skeptical of reports of very strong hallucinations... (It was primarily the telltale strength of the hallucinations reported by Carlos Castaneda in The Teachings of Don Juan: A Yaqui Way of Knowledge [19681 that first suggested to scientists that the book, in spite of having been a successful Ph.D. thesis in anthropology at UCLA, was fiction, not fact.)
Theme running through the book: Consciousness is treated by us much like
magic is.
a card magician has many standard ways of giving the victim the illusion
that he is exercising his free choice in what cards on the table he
examines, when in fact there is only one card that may be turned
over. p.10
[consciousness is like hallucinations that may be be produced in a brain], a
way that harnesses the very freewheeling curiosity of the victim. 10
from On Baars, “The double life of B.F. Skinner. . . “, by Daniel Dennett, 2002
Is consciousness real? Of course it is – as long as you don’t understand it as
magic, but for some people, consciousness is magic or it is nothing at all.
Are there really such people? Yes, many. Speaking for them, for instance, is
Robert Wright:
[from Robert Wright, 2000, Nonzero: the Logic of Human Destiny, Pantheon, p.425]
"I'm writing a book on magic." I explain, and I'm asked, "Real magic?" By
real magic people mean miracles, thaumaturgical acts, and supernatural
powers. "No." I answer: "Conjuring tricks, not real magic." ~ Lee Siegel,
in his fascinating history of Indian street magic, Net of Magic: Wonders
and Deceptions in India, (Univ. of Chicago Press, 1991)
Real magic in other words, refers to the magic that is not real, while the
magic that is real, that can actually be done, is /not real magic/. "
In our brains there is a cobbled-together collection of specialist
brain circuits, which, thanks to a faniily of habits inculcated partly by
culture and partly by individual self-exploration, conspire together to
produce a more or less orderly, more r less effective, more or less welldesigned
virtual machine, the Joyce:in machine. By yoking these independently
evolved specialist organs together in common cause, and
thereby giving their union vastly erhanced powers, this virtual machine,
this software of the brain, performs a sort of internal political
miracle: It creates a virtual captain of the crew, without elevating any
one of them to long-term dictatorial power. Who's in charge? First one
coalition and then another... p. 228
It looks magical, but as every stage magician knows, the appearance of magic
is heightened by the fact that an audience can generally be counted on to
exaggerate the phenomenon in need of explanation.
Stage magicians know that a collection of cheap tricks will often suffice to
produce "magic," and so does Mother the ultimate gadgeteer.
[Thus the brain too, is a set of cobbled together cheap tricks.
the fact that we find them difficult to see is because of an illusion we have
created for ourselves, the illusion of consciousness itself, which fills in
the huge gaps and creates this magical, coherent whole. This seems to be the
thrust of Dennett's arguments.
But perhaps the tricks aren't that cheap, after all! ]
In this game one person, the dupe, is told that while he is out of the room,
one member of the assembled party will be called upon to relate a recent
dream. This will give everybody else in the room the story line of that dream
so that when the dupe returns to the room and begins questioning the assembled
party, the dreamer's identity will be hidden in the crowd of responders. The
dupe's job is to ask yes/no questions of the assembled group until he has
figured out the dream narrative to a suitable degree of detail, at which point
the dupe is to psychoanalyze the dreamer, and use the analysis to identify him
or her.
Once the dupe is out of the room, the host explains to the rest of the party
that no one is to relate a dream, that the party is to answer the dupe's
questions according to the following simple rule: if the last letter of the
last word of the question is in the first half of the alphabet. the questions
is to be answered in the affirmative, and all other questions are to be
answered in the negative, with one proviso: a noncontradiction override rule
to the effect that later questions are not to be given answers that contradict
earlier answers. For example:
Q: Is the dream about a girl?
A: Yes.
but if later our forgetful dupe asks
Q: Are there any female characters in it?
A: Yes [in spite of the final t, applying the noncontradiction override]
When the dupe eventually relates the dream to a dreamer, the assembled party
gleefully retorts that the dupe himself is the author of the "dream." ... but
in one sense, the dream simply has no author, and that is the whole
point. Here we see a process of narrative production, of detail accumulation,
with no authorial intentions or plans at all — an illusion with no
illusionist.
[Argues that perception is similar in that it incorporates] a few
"expectation-driven" rounds of hypothesis testing. Theories of perception in
the 1980s (e.g., Neisser, 1967):
after a certain amount of "preprocessing" has occurred in the early or
peripheral layers of the perceptual system, objects are identified,
recognized, categorized — by generate-and-test cycles.
---
What distinguishes any old piece of matter from those
that we call "animate"? Why are some physical
patterns in the universe privileged of feeling sensations and having
experiences? Presents a strongly non-dualist view of consciousness. Much of
the first third of the book is an attack on cartesian duality. The middle
part deals with work (from 80s) in neuropsychology and AI and at artificial models that
Chapter 3: How are animals different from robots?
E.g. Descartes believed that animals were just elaborate machines. Human
bodies, and even human brains, were machines. It was only our nonmechanical,
nonphysical minds that make human beings [and only humans] intelligent and
conscious. p.43, footnote
Phenomenology: An umbrella term to cover all the items of conscious
experience: thoughts, smells, itches, imagined purple cows.
History of the term:
Kant: distinguishes "phenomena" - things as they appear, from "noumena",
things as they are. In the 19th c. Phenomenology = descriptive study of any
subject matter, in a neutral or pre-theoretical manner. The philosophical
school of Phenomenology dev 20th c around work by Edmund Husserl, aimed at
finding new foundation for all knowledge / philosophy. p.44-5
covers the fascinating work of Benjamin Libet: stimulations given to left hand, and to corresp part of the right somatosensory cortex. Both stimulations take about 500ms to reach "neuronal adequacy" - a conscious experience of a tingle. However, when stimulations are given to the hand, these are "automatically "referred backwards in time". More strikingly, Libet reported instances in which a patient's left cortex (right hand area) was stimulated before his left hand was ==> this should give rise to two tingles - first right hand (cortically induced) and then left hand. However, patients reported the opposite, "first left, then right". p.154-5]
It has long been known that stimulation of locations on the somatosensory cortex (a strip conveniently located across the top of the brain) produces the experience in the patient of sensations on corresponding parts of the body. For instance, stimulation of a point on the left somatosensory cortex can produce the sensation of a brief tingle in the subject's right hand. 154 Libet compared the time course of such cortically induced tingles to similar sensations produced in the more usual way, by applying a brief electrical pulse to the hand itself (Libet, 1965, 1981, 1982, 1985b; Libet et al., 1979; see also Popper and Ecclos, 1977; Dennett, 1979b; Churchland, 1981a, 1981b; Honderich, 1984:1. Libet asked his patients which came first, the hand-tingle that started in the cortex or the hand-tingle sent from the hand. From the data he gathered, he argued that while in each case it took considerable time (approximately 500 msec) from onset of stimulation to "neuronal adequacy" (the point at which he claims that cortical processes culminate to yield a conscious experience of a tingle), when the hand itself was stimulated, the experience was "automatically" "referred backwards in time," and was felt to happen before the tingle produced by brain stimulation itself. Most strikingly, Libet reported instances in which a patient's left cortex was stimulated before his left hand was stimulated, which one would tend to think would surely give rise to two felt tingles: first right hand (cortically induced) and then left hand. In fact, however, the subjective report was reversed: "first left, then right." Libet has interpreted his results as raising a serious challenge to materialism:". . . a dissociation between the timings of the corresponding and events would seem to raise serious though not insurmountable difficulties for the.. . theory of psychoneural identity" (Libet et al., 1979, p. 222). According to Sir John Eccies, a Nobel laureate in medicine for his research in neurophysiology, this challenge cannot be met: p.155 This antedating procedure does not seem to be explicable by any neurophysiological process. Presumably it is a strategy that has been learnt by the self-conscious mind. . . the antedating sensory experience is attributable to the ability of the self-conscious mind to make slight temporal adjustments, i.e., to play tricks with time. [Popper and Eccles, 1977, p. 3641 More recently, the mathematician and physicist Roger Penrose (1989) has suggested that a materialistic explanation of Libet's phenomena would require a revolution in fundamental physics. [lengthy discussion of proposals for how the paradox arises - the signal is back-referred to the hand, and then travels back etc....]
He asked normal subjects (not neurosurgery patients) to make "spontaneous" decisions to flex one hand at the wrist while noting the position of a spot on a revolving disk (the "second hand" on a clock, in effect) at the precise time they formed the intention (Libet, 1985a, 1987, 1989). Afterwards (a few seconds later), subjects reported where the spot was at the moment they decided to flex their wrist. ... found evidence that these "conscious decisions" lagged between 350 and 400msec behind the onset of "readiness potentials" he was able to record from scalp electrodes, concludes that "cerebral initiation of a spontaneous voluntary act begins unconsciously" (1 985a, p. 529). conscious intentions to act [at least in the Libet-an tasks] are put into registration with the brain events that actually initiate the acts, there is an offset in the 300-500msec range.
Owen Flannagan, Consciousness Reconsidered, chapter 3, section 3: [In reference to Daniel Dennett's Consciousness Explained, 1991), : The theory of "neural Darwinism" or "neuronal group selection" helps bring together and extend some of the insights about brain composition, structure, function, and evolution discussed so far (Edelman 1987, 1989; also see Changeux 1985). Five ideas are especially important. First, it is mathematically inconceivable that the human genome specifies the entire wiring diagram of the brain. The genome, powerful as it is, contains too few instructions by several orders of magnitiude to build a fully funcitonal brain. The synaptic connections that evolve in the brain over time are the complex causal outcome of genotypic instructions, endogenous biochemical processes, plus vast amounts of individually unique interactions between organism and environment (Edelman 1989, 30 Hundert 1989, 237). It follows that talk of the brain as hard-wired is misleading. To be sure, the overall structure of the brain is fixed by our genes and certain neuronal paths, and certain specific areas are designed to serve certain dedicated functions. But the "wires" in the brain are soft, even those built during fetal development and those serving specific functions. Furthermore, all the wires are capable of being drawn into novel and complex connections with indefinitely many other segments of the neural network. The key to our magnificent abilities as anticipation machines involves fixing gross architecture while leaving the development of connections at the microstructural level undedicated and adaptable. Second and relatedly, individual brains are extraordinarily diverse in terms of structure ond connectivity. Identity theory has some credibility in the domain of sensory experience. Certain characteristic neural patterns subserve similar cross-personal sensory experiences. But by and large most mental states probably do no involve strict identites between types of mental and neural states. Thus one and the same conscious mental state, for example, believing that a speeding fire engine is coming from behind, is almost certainly subserved by compositionally distinct neural states in all the different drivers who have that thought. Once massive connectivity is added in, it is no surprise that this thought kicks off a series of other, different thoughts for each of us. Once person worries about the victims and their property, and another that he will be delayed. A third is thrown into a Proustian reminiscence of summer nights in his childhood spent with grandfather, the fire chief, at the station. He feels the humid summer breeze on his face as he rides to a fire, and the smells of burning embers and pictures of lonely stone chimneys well up in him. Neural connectivity is the mother of "meaning holism" and the "drift of thought" the way the meaning of each term connects idiosyncratically with the meaning of many others. We are good at keeping attention focused, but certain events send thought reeling to unanticipated places, some welcome, others not. Neural connectivity helps explain why this happens so easily. The third, fourth, and fifth theses of neural Darwinism further clarify the prospect for a complex form of mind-brain identity theory and indicate some of the problems such a theory will face. The third thesis is that neuronal ensembles projecting through many levels are selected during experiences to map and thereby to represent certain saliencies. Which ensembles represent what is jointly determined by the genetically specified receptivities of different neural locaitons (so visual processing takes place in areas dedicated to vision and not to audition) and by the neuronal groups available for selection and strengthening at the time a stimulus is presented. But the jobs of all ensembles are not assigned in advance, as they are, for example, on the view that the mind contains all concepts innately. On such a view, experience merely acts to trigger what is there (Fodor 1975, 1981). On the neural-selctionist view, the brain is a vast territory with contours roughed out by nature and more than enough room for all comers. Experiences come looking for squatter's rights, for room to make a life. The brain makes room in various ways. Sometimes it simply gives over unclaimed terrain; other times it sets up time-sharing and multiple-tenancy arrangements. Selection is involved in that the world plays an important part in determining which neuronal groups are activated for what roles. It does not simply trigger neuronal groups preset to work for a particular boss, should he turn up, and give the marching orders they passively await. Nonetheless, once a neuronal group is assigned to a task, that group shows up regularly for the job. Fourth and relatedly, the neuronal network retains representations, but not in permanently coded files. It retains representations as dispositions to reactivate distributed activation patterns selected during previous experience. Once a particular distributed activation pattern has reached an equilibrial state so that it is activated by a certain type of stimulus pattern, it frames novel occurent stimulation with that activation pattern. This leads to quick and easy identification of the stimulation and, depending on its connections to other neuronal groups, to the right motor repsponse. The neuronal groups are selected to detect certain constellations of features. The groups are extremely sensitive but not overly fussy. This explains why we are so quick to identify degraded stimuli, for example, letters written in new and obscure handwriting. The right pattern of activation is turned on by any stimulus that possesses a sufficient number, or some adquately patterned configuration, of the relevant features. The stimuli need not be exactly the same as the stimuli that the neuronal group was initially trained to detect. Indeed, a system that could only recognize duplicates of previous stimuli would be of no use at all in our fluid ecological surround. Recognition and recall do not involve permanent storage, and thus lost space each time a particular pattern becomes recognizable. Rather, neuronal groups play multiple roles. My red detectors are activated whenever red is before me. But when red things are not before me, my red detectors are available for other recongitional labor- purple and orange detection, for example. Fifth, a neuronal system functioning according to principles of ontogenic (lifespan) selection, as opposed to phylogenic (species-level) selection, is fluid in several repects: (1) It can gain, retain, revise, and abandon all sorts of thoughts, ideas, desires, and intentions in the course of a life. (2) The system can lose certain neurons to death, or in a labor dispute, one function can lose neurons to some other function, without any loss in functional capacity. If the capacity to recognize a banana as edible is subserved by parallel activity in numerous recurrent layers of neuronal groups, then all manner of degradation and loss of members is compatible with continuous high performance. Neuronal destruction can, of course, reach a point where the amount of neuronal degradation is great enough to lead to functional incapacitation in certain domains, as it does, for example, in Alzheimer's patients. (3) Neuronal dedication to a task is not fixed for all time once the neuronal group subserving the recognitional or motor task in question is well honed. For example, the neuronal group responsible for pressure detection on two adjacent fingers wil "segregate into groups that at any one time are nonoverlapping and have sharp boundaries" (Edelman 1989, 52). But these dedicated groups can shift boundaries over time because of differential experience, or possibly even randomly. Imagine the boundary between the United States and Canada shifting several miles one way or the other each day along its entire expanse (Calvin 1990, 175).