Philosophy E156: Philosophy of Mind

Week 12: Dennett’s Multiple Drafts Model and

the Case Against Filling In

Cartesian Materalism• Descartes believed not only in dualism, that we are

made up of both brain and soul, but that there was a point in the brain where everything came together before it was sent across a psychophysical bridge into the soul

• He located that point in the pineal gland, located between the two hemispheres

• Dennett ridicules the non-dualist vestige of such a view as “Cartesian materialism” (CE, p. 107):– “the view you arrive at when you discard Descartes’s

dualism but fail to discard the imagery of a central (but material) Theater where ‘it all comes together’”

The Cartesian Theater• “The Cartesian Theater is a metaphorical picture

of how conscious experience must sit in the brain.

• “It seems at first to be an innocuous extrapolation of the familiar and undeniable fact that for everyday, macroscopic time intervals, we can indeed order events into the two categories ‘not yet observed’ and ‘already observed.’

• “We do this by locating the observer at a point and plotting the motions of the vehicles of information relative to that point.”

Problem with the Cartesian Theater Metaphor

• “But when we try to extend this method to explain phenomena involving very short time intervals, we encounter a logical difficulty:

• If the ‘point’ of view of the observer must be smeared over a rather large volume in the observer’s brain, the observer’s own subjective sense of sequence and simultaneity must be determined by something other than ‘order of arrival,’ since order of arrival is incompletely defined until the relevant destination is specified.”

Three Puzzle Cases

• Nelson Goodman’s & Paul Kolers’ “color phi” experiment

• Geldard & Sherrick’s “cutaneous rabbit” experiment

• Benjamin Libet’s “backward referral in time” cases

Phi Phenomenon

• http://upload.wikimedia.org/wikipedia/commons/6/6e/Lilac-Chaser.gif

Color Phi Demonstration

• http://www.philosophy.uncc.edu/faculty/phi/Phi_Color2.html

Color Phi Demonstration

• http://highered.mcgraw-hill.com/sites/0070579431/student_view0/chapter8/phi_phenomenon_activity.html

Color Phi Penomenon

The Cutaneous Rabbit Illusion

• http://video.search.yahoo.com/search/video;_ylt=A0geuqHVbYJSFmoAWkpXNyoA?p=Cutaneous+rabbit+illusion&fr=yfp-t-600&fr2=piv-web

Dennett’s Question

• “Now, at first one feels like asking how did the brain know that after the five taps on the wrist, there were going to be some taps near the elbow?” (CE, p. 143)

Libet’s Experimental Results

• Benjamin Libet ran experiments on willing subjects during brain surgery

• He discovered a 500-millisec delay between the physical prodding of a part of the brain and the conscious awareness associated with that brain part

• Normal stimulation of the brain by stimulation of the skin is faster – as required if anything is achievable in a timely way

• Libet explained the discrepancy by positing “backward referral in time” – mental causation begins in unconsciousness & consciousness backdates experience to seem as if it was conscious from the start

Eccles Claims Libet’s Results Are Inconsistent with Physicalism

• Eccles: “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.”

Penrose Claims Libet’s Results Are Inconsistent with Ordinary Physicalism• Penrose: “[W]e seem to be driven to the conclusion that in

any action in which an external stimulus leads to a consciously controlled response, a time delay of some one and one-half seconds would seem to be needed before that response can occur. For awareness would not even take place until half a second has passed; and if that awareness is to be put to use, then the apparently sluggish machinery of free will would then have to be brought into play, with perhaps another second's delay.... [I]f, in some manifestation of consciousness, classical reasoning about the temporal ordering of events leads us to a contradictory conclusion, then this is a strong indication that quantum actions are indeed at work!”

The Multiple Drafts Model

• Dennett tries to explain these effects by positing parallel processing in the brain of sensory inputs that involves constant interpretation and revision, but only a single detection and discrimination, and no re-presentation.

Julesz Random-Dot Stereogram

To construct a random-dot stereogram, you first place a bunch of dots randomly in an image. Then make two copies of it. In one copy shift a central square region to the left and in the other copy shift the same central square region to the right. This leaves holes in each of the images (left over from where the square shifted from). Fill the holes with new random dots. Why do you see it in 3D? The shift mimics differences which ordinarily exist between the views of genuine 3D objects. The extra dots (X and Y above) correspond to those parts of the background that one eye can see, but which are occluded from the view of the other eye by the foreground square.

(http://www.cns.nyu.edu/~david/courses/perception/lecturenotes/depth/depth-size.html)

Orwellian & Stalinesque Falsifications of Experience

• On reflection, we should – and often do – recognize possibility of falsification in constructing experience

• Dennett takes this lesson from Descartes, although I say Descartes himself recognizes this possibility

• Two kinds of falsification are possible– pre-experiential– post-experiential

• Pre-experiential falsification Dennett calls “Stalinesque,” because of Stalin’s show trials

• Post-experiential falsification Dennett calls “Orwellian,” because of Orwell’s Ministry of Truth

Orwellian Revisions

Orwellian Revisions

• The paradigm Orwellian device is the construction of false memories

Orwellian Revisions

• The paradigm Orwellian device is the construction of false memories

• Dennett tells a story about your seeing a long-haired woman but one second later having the experience contaminated by a memory of a short-haired woman with glasses

Orwellian Revisions

• The paradigm Orwellian device is the construction of false memories

• Dennett tells a story about your seeing a long-haired woman but one second later having the experience contaminated by a memory of a short-haired woman with glasses

Orwellian Revisions

• The paradigm Orwellian device is the construction of false memories

• Dennett tells a story about your seeing a long-haired woman but one second later having the experience contaminated by a memory of a short-haired woman with glasses

• This causes you to falsely report having seen a long-haired woman with glasses

Orwellian Revisions

• The paradigm Orwellian device is the construction of false memories

• Dennett tells a story about your seeing a long-haired woman but one second later having the experience contaminated by a memory of a short-haired woman with glasses

• This causes you to falsely report having seen a long-haired woman with glasses

• An “Orwellian revision” of your experience

Stalinesque Falsifications

Stalinesque Falsifications

• The paradigm Stalinesque device is hallucination

Stalinesque Falsifications

• The paradigm Stalinesque device is hallucination

• Imagine that your having the memory of the short-haired woman with glasses causes you to hallucinate the eyeglasses onto the long-haired woman

Stalinesque Falsifications

• The paradigm Stalinesque device is hallucination

• Imagine that your having the memory of the short-haired woman with glasses causes you to hallucinate the eyeglasses onto the long-haired woman

Stalinesque Falsifications

• The paradigm Stalinesque device is hallucination

• Imagine that your having the memory of the short-haired woman with glasses causes you to hallucinate the eyeglasses onto the long-haired woman

• Unlike the first case, it is this hallucination which causes you to falsely report having seen a long-haired woman with glasses

Stalinesque Falsifications

• The paradigm Stalinesque device is hallucination• Imagine that your having the memory of the

short-haired woman with glasses causes you to hallucinate the eyeglasses onto the long-haired woman

• Unlike the first case, it is this hallucination which causes you to falsely report having seen a long-haired woman with glasses

• “Stalinesque falsification” of your experience

No Distinction

• In some cases, Dennett argues, there might be no distinction between the Orwellian and the Stalinesque falsification

• We have the idea that there must be, he argues, because we have the idea that there must be an “actual conscious experience” even if we are unable to report it

• This is just the idea of the Cartesian Theater• There is “no privileged finish line,” he says

Orwellian & Stalinesque Interpretations of Color Phi

Orwellian & Stalinesque Interpretations of Color Phi

• Hypothesis of a Stalinesque mechanism:

Orwellian & Stalinesque Interpretations of Color Phi

• Hypothesis of a Stalinesque mechanism:– “In the brain’s editing room, located before consciousness, there is a

delay, a loop of slack like the tape delay used in broadcasts of ‘live’ programs, which gives the censors in the control room a few seconds to bleep out obscenities before broadcasting the signal” (CE, p. 120)

Orwellian & Stalinesque Interpretations of Color Phi

• Hypothesis of a Stalinesque mechanism:– “In the brain’s editing room, located before consciousness, there is a

delay, a loop of slack like the tape delay used in broadcasts of ‘live’ programs, which gives the censors in the control room a few seconds to bleep out obscenities before broadcasting the signal” (CE, p. 120)

• Hypothesis of an Orwellian mechanism:

Orwellian & Stalinesque Interpretations of Color Phi

• Hypothesis of a Stalinesque mechanism:– “In the brain’s editing room, located before consciousness, there is a

delay, a loop of slack like the tape delay used in broadcasts of ‘live’ programs, which gives the censors in the control room a few seconds to bleep out obscenities before broadcasting the signal” (CE, p. 120)

• Hypothesis of an Orwellian mechanism:– “shortly after the consciousness of the first spot and the second spot

(with no illusion of apparent motion at all), a revisionist historian of sorts, in the brain’s memory-library receiving station, notices that the unvarnished history in this instance doesn’t make enough sense, so he interprets the brute events, red-followed-by-green, by making up a narrative about the intervening passage, complete with mid-course color change, and installs this history….” (CE, pp. 120-1)

Filling In: Pigment & Figment

• The Stalinesque story requires “filling in” experience with different content – in a hallucination-like way

• Thus, the Stalinesque account can say that the subject before responding to it was conscious of the red spot

• Thus, it is thought that there is a fact of the matter about the content of consciousness

• Dennett is suspicious of appeals to “filling in”• Paint uses pigment – filling in, he says, uses

“figment”

“Filling in” the Blind Spot

• The blind spot is the hole in the visual field corresponding to the place the optic nerve connects with the retina

• According to one standard account, it is “roughly 7.5° high and 5.5° wide”

• It is not ordinarily noticed• It is often thought to be “filled in” with characteristics of what

surrounds it – that this is why it’s not noticed– Hardin claims that “the eye-brain fills in with whatever is seen in

the adjoining regions. If that is blue, it fills in blue; if it is plaid, we are aware of no discontinuity in the expanse of plaid.”

“Filling in” with Neon Color Spreading

Dennett’s Grid from the Back Cover of Consciousness Explained

The Neon Color Spreading Illusion

• Dennett, CE, p. 351: “The pink you see filling in the ring defined by the red lines is not the result of pink smudging on the page, or light scattering. There is no pink on your retinal image, in other words, in addition to the red lines. Now how might this illusion be explained?”

• Two hypotheses:– The “misled brain” hypothesis– The “filling in” hypothesis

The “misled brain” hypothesis

• “One brain circuit, specializing in shape, is misled to distinguish a particular bounded region: the ring with its ‘subjective contours.’… Another brain circuit, specializing in color but rather poor on shape and location, comes up with a color discrimination (pink #97, let’s say) with which to ‘label’ something in the vicinity, and the label gets attached (or ‘bound’) to the whole region. Why these particular discriminations should occur under these conditions is still controversial, but the controversy concerns the causal mechanisms that lead to mislabeling the region, not the further ‘products’ (if any) of the visual system.”

The “misled brain” hypothesis: Mislabeling “Pink #97”

The “filling in” hypothesis

• “But isn’t there something missing? I have stopped short at an explanation that provides a labeled color-by-numbers region: Doesn’t that recipe for a colored image have to be executed somewhere? Doesn’t pink #97 have to be ‘filled in’? After all, you may be tempted to insist, you see the pink! You certainly don’t see an outlined region with a number written in it. The pink you see is not in the outside world (it isn’t pigment or dye or ‘colored light’), so it must be ‘in here’ – pink figment, in other words.”

The Representationalist Position

• “The question of whether the brain ‘fills in’ in one way or another is not a question on which introspection by itself can bear…. [I]ntrospection provides us – the subject as well as the ‘outside’ experimenter – only with the content of representation, not with the features of the representational medium itself. For evidence about the medium, we need to conduct further experiments. But for some phenomena, we can already be quite sure that the medium of representation is a version of something efficient, like color-by-numbers, not roughly continuous, like bit-mapping.”

“Filling in” Marilyns

• Dennett’s Marilyns example (CE, p. 354):• “Suppose you – a walk into a room and notice

that the wallpaper is a regular array of hundreds of … – let’s pay homage to Andy Warhol – identical photographic portraits of Marilyn Monroe….”

Dennett’s

• “In order to identify a picture as a portrait of Marilyn Monroe, you have to foveate the picture: the image has to fall on the high resolution foveae of your eyes. . .Yet we know that if you were to enter a room whose walls were papered with identical photos of Marilyn Monroe, you would “instantly” see that this was the case. You would see in a fraction of a second that there were “lots and lots of identical, detailed, focused portraits of Marilyn Monroe.” Since your eyes saccade four or five times a second at most, you could foveate only one or two Marilyns in the time it takes you to jump to the conclusion and thereupon to see hundreds of identical Marilyns.”

Denett’s Representationalist Account of What’s Going On

• “Your brain just somehow represents that there are hundreds of identical Marilyns, and no matter how vivid your impression is that you see all that detail, the detail is in the world, not in your head.”

Dennett Rejects the “Photocopying” Hypothesis, a Version of “Filling In”

• “Now, is it possible that the brain takes one of its high-resolution foveal views of Marilyn and reproduces it, as if by photocopying, across an internal mapping of the expanse of wall? That is the only way the high-resolution details you used to identify Marilyn could ‘get into the background’ at all, since parafoveal vision is not sharp enough to provide it by itself. I suppose it is possible in principle, but the brain almost certainly does not go to the trouble of doing that filling in!”

Dennett: the Brain Is Not “Providing” but “Ignoring”

• At the end of the section on “filling in” (CE, p. 356), Dennett argues the “filling in” hypothesis “suggests that the brain is providing something when in fact the brain is ignoring something.”

• He rejects Edelman’s assertion: “One of the most striking features of consciousness is its continuity.”

• Dennett responds:– “This is utterly wrong. One of the most strking features of consciousness is

its discontinuity – as revealed in the blind spot, and saccadic gaps, to take the simplest examples. The discontinuity of consciousness is striking because of the apparent continuity of consciousness.”

• Let me make the fairly obvious point that what Edelman writes of – consciousness’s continuity – is completely compatible with what Dennett writes of – the discontinuity of consciousness

Is Dennett’s Argument Strong Enough?

• Notice Dennett’s language: “I suppose it is possible in principle, but the brain almost certainly….”

• If it is possible in principle, then it is not clear what the issue is• Is the issue only that often there is no “filling in” even though there seems to be?• After all, he is rejecting what he takes to be a Cartesian idea of privileged access• And he has argued that we have access to the content, not to the medium• But both the case against the Cartesian theater and the case for

representationalism would seem to require a strong argument• It would seem to seem to require that there is never “filling in” because

– (1) there is nothing to fill in with (i.e., figment), and – (2) there is nothing to “fill in” (the theater)

• He does not seem to provide evidence for a stronger argument