America and when of consciousness in the brain

s We compare the way two models of consciousness treat subjective timing. According to the standard "Cartesian Theater" model, there is a place in the brain where "it all comes together," and the discriminations in all modalities are somehow put into registration and "presented" for subjective judgment. The timing of the events in this theater determines subjective order. According to the alternative "Multiple Drafts" model, discriminations are distributed in both space and time in the brain. These events do have temporal properties, but those properties do not determine subjective order because there is no single, definitive "stream of consciousness," only a parallel stream of conflicting and continuously revised contents. Four puzzling phenomena that resist explanation by the Cartesian model are analyzed: (1) a gradual apparent motion phenomenon involving abrupt color change (Kolers & von Griinau 1976), (2) an illusion of an evenly spaced series of "hops" produced by two or more widely spaced series of taps delivered to the skin (Geldard & Sherrick's "cutaneous rabbit" [1972]), (3) backwards referral in time, and (4) subjective delay of consciousness of intention (both reported in this journal by LIbet 1985a; 1987; 1989a). The unexamined assumptions that have always made the Cartesian Theater so attractive are exposed and dismantled. The Multiple Drafts model provides a better account of the puzzling phenomena, avoiding the scientific and metaphysical extravagances of the Cartesian Theater: The temporal order of subjective events is a product of the brain's interpretational processes, not a direct reflection of events making up those processes. Keywords? consciousness; discrimination; illusion; localization; memory; mental timing; perception; subjective experience I'm really not sure if others fail to perceive me or if, one fraction of a second after my face interferes with their horizon, a millionth of a second after they have cast their gaze on me, they already begin to wash me from their memory: forgotten before arriving at the scant, sad archangel of a remembrance. Ariel Dorfman, Mascara, 1988 When scientific advances contradict "common sense" Intuitions, the familiar Ideas often linger on, not just outliving their usefulness but even confusing the scientists whose discoveries ought to have overthrown them. Diagnosed here is a ubiquitous error of thinking that arises from just such a misplaced allegiance to familiar images, Illustrated with examples drawn from recent work in psychology and neuroscience. Although this Is a "theoretical" paper, It is addressed especially to those who think, mistakenly, that they have no theories and no need for theories. We show how uncontroversial facts about the spatial and temporal properties of informationbearing events In the brain require us to abandon a family of entrenched intuitions about "the stream of consciousness" and its relation to events occurring in the brain. In Section 1, we Introduce two models of consciousness, the standard Cartesian Theater and our alternative, the Multiple Drafts model, briefly describing four phenomena of temporal Interpretation that raise problems for the standard model. Two of these, drawn from the research of Libet, have been extensively debated on methodological grounds, but concealed In the controversy surrounding them are the mistaken assumptions we expose. In Section 2, we diagnose these Intuitive but erroneous Ideas and exhibit their power to create confusion in relatively simple contexts. We demonstrate the superiority of the Multiple Drafts model of consciousness by showing how it avoids the Insoluble problems faced by versions of the Cartesian Theater. In Section 3, we show how covert allegiance to the Cartesian Theater has misled Interpreters of Libet's phenomena and how the Multiple Drafts model avoids these confusions. 1. Two models of consciousness 1.1. Cartesian materialism: Is there a "central obserwer" in the brain? Wherever there is a conscious mind, there is a point of view. A conscious mind is an observer who takes in the information that Is available at a particular (roughly) continuous sequence of times and places In the universe. A mind is thus a locus of subjectivity, a thing it is like something to be (Farrell 1950; Nagel 1974). What it Is like to be that thing is partly determined by what Is available to be observed or experienced along the trajectory through space-time of that moving point of view, which for most practical purposes Is just that: a point. For instance, the startling dissociation of the sound and appearance of distant fireworks Is explained by the different 1992 Cambridge University Press 0140-525X192 $5.00+.00 183 Dennett & Kinsbourne: Time and the observer transmission speeds of sound and light, arriving at the observer (at that point) at different times, even though they left the source simultaneously. But if we ask where precisely in the brain that point of view is located, the simple assumptions that work so well on larger scales of space and time break down. It is now quite clear that there is no single point in the brain where all information funnels In, and this fact has some far from obvious consequences. Light travels much faster than sound, as the fireworks example reminds us, but it takes longer for the brain to process visual stimuli than to process auditory stimuli. As Poppel (1985/1988) has pointed out, thanks to these counterbalancing differences, the "horizon of simultaneity" Is about 10 meters: Light and sound that leave the same point about 10 meters from the observer's sense organs produce neural responses that are "centrally available" at the same time. Can we make this figure more precise? There is a problem. The problem is not just measuring the distances from the external event to the sense organs, or the transmission speeds in the various media, or allowing for individual differences. The more fundamental problem Is deciding what to count as the "finish line" In the brain. Poppel obtained his result by comparing behavioral measures: mean reaction times (button-pushing) to auditory and visual stimuli. The difference ranges between 30 and 40 msec, the time It takes sound to travel approximately 10 meters (the time It takes light to travel 10 meters is only infinitesimally different from zero). Poppel used a peripheral finish line external behavior but our natural Intuition is that the experience of the light and sound happens between the time the vibrations strike our sense organs and the time we manage to push the button to signal that experience. And It happens somewhere centrally, somewhere In the brain on the excited paths between the sense organ and muscles that move the finger. It seems that If we could say exactly where the experience happened, we could infer exactly when It happened. And vice versa: If we could say exactly when it happened, we could infer where In the brain conscious experience was located. This picture of how conscious experience must sit In the brain Is a natural extrapolation of the familiar and undeniable fact that for macroscopic time intervals, we can Indeed order events into the categories "not yet observed" and "already observed" by locating the observer and plotting the motions of the vehicles of information relative to that point. But when we aspire to extend this method to explain phenomena involving very short intervals, we encounter a logical difficulty: If the "point" of view of the observer is spread 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 a unique "order of arrival" because order of arrival Is Incompletely defined until we specify the relevant destination. If A beats B to one finish line but B beats A to another, which result fixes subjective sequence In consciousness (cf. Minsky 1985, p. 61)? Which point or points of "central availability" would "count" as a determiner of experienced order, and why? Consider the time course of normal visual information processing. Visual stimuli evoke trains of events In the cortex that gradually yield content of greater and greater specificity. At different times and different places, various "decisions" or "judgments" are made: More literally, parts of the brain are caused to go into states that differentially respond to different features, for example, first mere onset of stimulus, then shape, later color (In a different pathway), motion, and eventually object recognition. It Is tempting to suppose that there must be some place in the brain where "It all comes together" in a multimodal representation or display that is definitive of the content of conscious experience in at least this sense: The temporal properties of the events that occur in that particular locus of representation determine the temporal properties of sequence, simultaneity, and real-time onset, for instance — of the subjective "stream of consciousness." This is the error of thinking we intend to expose. Where does it all "come together?" The answer, we propose, is nowhere. Some of the contentful states distributed around in the brain soon die out, leaving no traces. Others do leave traces,, on subsequent verbal reports of experience and memory, on "semantic readiness" and other varieties of perceptual set, on emotional state, behavioral proclivities, and so forth. Some of these effects for instance, influences on subsequent verbal reports are at least symptomatic of consciousness. But there Is no one place In the brain through which all these causal trains must pass to deposit their contents "In consciousness" (see also Damasio 1989a). The brain must be able to "bind" or "correlate" and "compare" various separately discriminated contents, but the processes that accomplish these unifications are themselves distributed, not gathered at some central decision point, and as a result, the "point of view of the observer" Is spatially smeared. If brains computed at near the speed of light, as computers do, this spatial smear would be negligible. But given the relatively slow transmission and computation speeds of neurons, the spatial distribution of processes creates significant temporal smear ranging, as we shall see, up to several hundred milliseconds within which range the normal commonsense assumptions about timing and arrival at the observer need to be replaced. For many tasks, the human capacity to-make conscious discriminations of temporal order drops to chance when the difference in onset Is on the order of 50 msec (depending on stimulus conditions), but this variable threshold Is the result of complex Interactions, not a basic limit on the brain's capacity to make the specialized order judgments required in the Interpretation and coordination of perceptual and motor phenomena. We need other principles to explain the ways subjective temporal order is composed, especially in cases in which the brain must cope with rapid sequences occurring at the limits of its powers of temporal resolution. As usual, the performance of the brain when put under strain provides valuable clues about Its general modes of operation. Descartes, early (1664) to think seriously about what must happen Inside the body of the observer, elaborated an Idea that Is superficially so natural and appealing that it has permeated our thinking about consciousness ever since and permitted us to defer considering the perplexities until now. Descartes decided that the brain did have a center: the pineal gland, which served as the gateway to the conscious mind. This was the only organ In the brain that was in the midline, rather than paired, with left and right versions. The pineal looked different, and because its function was then quite inscrutable (and still 184 BEHAVIORAL AND BRAIN SCIENCES (1992) 15:2 Dennett & Kinsbourne: Time and the observer is), Descartes posited a role for it: For a person to be conscious of something, traffic from the senses had to arrive at this station, where it thereupon caused a special indeed magical transaction to occur between the person's material brain and immaterial mind. When the conscious mind then decided on a course of bodily action, it sent a message back "down" to the body via the pineal gland. The pineal gland, then, is like a theater in which information is displayed for perusal by the mind. Descartes' vision of the pineal's role as the turnstile of consciousness (we might call it the Cartesian bottleneck) is hopelessly wrong. The problems that face Descartes' interactionistic dualism, with its systematically inexplicable traffic between the realm of the material and the postulated realm of the immaterial, were already well appreciated in Descartes' own day, and centuries of reconsideration have only hardened the verdict: The idea of the Ghost in the Machine, as Ryle (1949) aptly pilloried it, is a nonsolution to the problems of mind. But whereas materialism of one sort or another is now a received opinion approaching unanimity, even the most sophisticated materialists today often forget that once Descartes' ghostly res cogitans is discarded, there is no longer a role for a centralized gateway, or indeed for any functional center to the brain. The brain itself is Headquarters, the place where the ultimate observer is, but it is a mistake to believe that the brain has any deeper headquarters, any inner sanctum, arrival at which is the necessary or sufficient condition for conscious experience. Let us call the idea of such a centered locus in the brain Cartesian materialism, because it is the view one arrives at when one discards Descartes' dualism but fails to discard the associated imagery of a central (but material) theater where "it all comes together." Once made explicit, it is obvious that this is a bad idea, not only because, as a matter of empirical fact, nothing in the functional neuroanatomy of the brain suggests such a general meeting place, but also because positing such a center would apparently be the first step in an infinite regress of toopowerful homunculi. If all the tasks Descartes assigned to the immaterial mind have to be taken over by a "conscious" subsystem, its own activity will either be systematically mysterious or decomposed into the activity of further subsystems that begin to duplicate the tasks of the "nonconscious" parts of the whole brain. Whether or not anyone explicitly endorses Cartesian materialism, some ubiquitous assumptions of current theorizing presuppose this dubious view. We show that the persuasive imagery of the Cartesian Theater, in its materialistic form, keeps reasserting itself, in diverse guises, and for a variety of ostensibly compelling reasons. Thinking in its terms is not an innocuous shortcut; it is a bad habit. One of its most seductive implications is the assumption that a distinction can always be drawn between "not yet observed" and "already observed." But, as we have just argued, this distinction cannot be drawn once we descend to the scale that places us within the boundaries of the spatiotemporal volume in which the various discriminations are accomplished. Inside this expanded "point of view," spatial and temporal distinctions lose the meanings they have in broader contexts. The crucial features of the Cartesian Theater model can best be seen by contrasting it with the alternative we propose, the Multiple Drafts model: All perceptual operations, and indeed all operations of thought and action, are accomplished by multitrack processes of interpretation and elaboration that occur over hundreds of milliseconds, during which time various additions, incorporations, emendations, and overwritings of content can occur, in various orders. Featuredetections or discriminations have to be made only once. That is, once a localized, specialized "observation" has been made, the information content thus fixed does not have to be sent somewhere else to be ^discriminated by some "master" discriminator. In other words, it does not lead to a re-presentation of the already discriminated feature for the benefit of the audience in the Cartesian Theater. How a localized discrimination contributes to, and what effect it has on the prevailing brain state (and thus awareness) can change from moment to moment, depending on what else is going on in the brain. Drafts of experience can be revised at a great rate, and no one is more correct than another. Each reflects the situation at the time it is generated. These spatially and temporally distributed content-fixations are themselves precisely locatable in both space and time, but their onsets do not mark the onset of awareness of their content. It is always an open question whether any particular content thus discriminated will eventually appear as an element in conscious experience. These distributed contentdiscriminations yield, over the course of time, something rather like a narrative stream or sequence, subject to continual editing by many processes distributed around in the brain, and continuing indefinitely into the future (cf. Calvin's [1990] model of consciousness as "scenariospinning"). This stream of contents is only rather like a narrative because of its multiplicity; at any point in time there are multiple "drafts" of narrative fragments at various stages of "editing" in various places in the brain. Probing this stream at different intervals produces different effects, elicits different narrative accounts from the subject. If one delays the probe too long (overnight, say) the result is apt to be no narrative left at all or else a narrative that has been digested or "rationally reconstructed" to the point that it has minimal integrity. If one probes "too early," one may gather data on how early a particular discrimination is achieved in the stream, but at the cost of disrupting the normal progression of the stream. Most important, the Multiple Drafts model avoids the tempting mistake of supposing that there must be a single narrative (the "final" or "published" draft) that is canonical that represents the actual stream of consciousness of the subject, whether or not the experimenter (or even the subject) can gain access to it. The main points at which this model disagrees with the competing tacit model of the Cartesian Theater, may be summarized: 1. Localized discriminations are not precursors of re-presentations of the discriminated content for consideration by a more central discriminator. 2. The objective temporal properties of discriminatory states may be determined, but they do not determine temporal properties of subjective experience. 3. The "stream of consciousness" is not a single,, definitive narrative. It is a parallel stream of conflicting and continuously revised contents, no one narrative thread of which can be singled out as canonical as the true version of conscious experience. BEHAVIORAL AND BRAIN SCIENCES (1992) 15:2 185 Dennett & Kinsbourne: Time and the observer The different implications of these two models will be exhibited by considering several puzzling phenomena that seem at first to indicate that the mind "plays tricks with time." (Other implications of the Multiple Drafts model are examined at length in Dennett 1991b.) 1.2. Some "temporal anomalies" of consciousness. Under various conditions people report experiences in which the temporal ordering of the elements in their consciousness, or the temporal relation of those elements to concurrent activity in their brains, seems to be anomalous or even paradoxical. Some theorists (Libet 1982; 1985a; Popper & Eccles 1977) have argued that these temporal anomalies are proof of the existence of an immaterial mind that interacts with the brain in physically inexplicable fashion. Others (Goodman 1978; Libet 1985b), although eschewing any commitment to dualism, have offered interpretations of the phenomena that seem to defy the accepted temporal sequence of cause and effect. Most recently, another theorist (Penrose 1989 see also multiple book review in BBS 13 (4) 1990) has suggested that a materialistic explanation of these phenomena would require a revolution in fundamental physics. These radical views have been vigorously criticized, but the criticisms have overlooked the possibility that the appearance of anomaly in these cases results from conceptual errors that are so deeply anchored in everyday thinking that even many of the critics have fallen into the same traps. We agree with Libet and others that these temporal anomalies are significant, but we hold a different opinion about what they signify. We focus on four examples, summarized below. Two, drawn from the work of Libet, have received the most attention and provoked the most radical speculation, but because technical criticisms of his experiments and their interpretation raise doubts about the existence of the phenomena he claims to have discovered, we begin with a discussion of two simpler phenomena whose existence has not been questioned but whose interpretation raises the same fundamental problems. We use these simpler cases to illustrate the superiority of the Multiple Drafts model to the traditional Cartesian Theater model, and then apply the conclusions drawn in the more complicated setting of the controversies surrounding Libet's work. Our argument is that even if Libet's phenomena were not known to exist, theory can readily account for the possibility of phenomena of this pseudo-anomalous sort, and even predict them. hie Many experiments have demonstrated the existence of apparent motion, or the phi phenomenon (Kolers & von Griinau 1976; see also Kolers 1972; van der Waals & Roelofs 1930; and the discussion in Goodman 1978). If two or more small spots separated by as much as 4 degrees of visual angle are briefly lit in rapid succession, a single spot will seem to move. This is the basis of our experience of motion in motion pictures and television. First studied systematically by Wertheimer (1912; for a historical account, see Kolers 1972; Sarris 1989), phi has been subjected to many variations; one of the most striking is reported in Kolers and von Griinau (1976). The philosopher Nelson Goodman had asked Kolers whether the phi phenomenon would persist if the two illuminated spots were different in color, and if so, what would happen to the color of "the" spot as "it" moved? Would the illusion of motion disappear, to be replaced by two separately flashing spots? Would the illusory "moving" spot gradually change from one color to another, tracing a trajectory around the color wheel? The answer, when Kolers and von Griinau performed the experiments, was striking: The spot seems to begin moving and then to change color abruptly in the middle of its illusory passage toward the second location. Goodman wondered: "How are we able . . . to fill in the spot at the intervening placetimes along a path running from the first to the second flash before that second flash occurs?" (1978, p. 73; the same question can be raised about any phi, but the colorswitch in midpassage vividly brings out the problem.) Unless there is p recognition, the illusory content cannot be created until after some identification of the second spot occurs in the brain. But if this identification of the second spot is already "in conscious experience" would it not be too late to interpose the illusory color-switchingwhile-moving scene between the conscious experience of spot 1 and the conscious experience of spot 2? How does the brain accomplish this sleight-of-hand? Van der Waals and Roelofs (1930) proposed that the intervening motion is produced retrospectively, built only after the second flash occurs, and "projected backwards in time" (Goodman 1978, p. 74), a form of words reminiscent of Libet's "backwards referral in time." But what does it mean that this experienced motion is "projected backwards in time"? cutaneous "rabbit" The subject's arm rests cushioned on a table, and mechanical square-wave tappers are placed at two or three locations along the arm, up to afoot apart (Geldard & Sherrick 1972; see also Geldard 1977; Geldard & Sherrick 1983; 1986). A series of rhythmical taps is delivered, for example, 5 at the wrist followed by 2 near the elbow and then 3 more on the upper arm. These taps are delivered with interstimulus intervals of between 50 and 200 msec. So a train of taps might last less than a second, or as long as two or three seconds. The astonishing effect is that the taps seem to the subjects to travel in regular sequence over equidistant points up the arm as if a little animal were hopping along the arm. Now how did the brain know that after the 5 taps on the wrist there were going to be some taps near the elbow? The experienced "departure" of the taps from the wrist begins with the second one, yet in catch trials in which the later elbow taps are never delivered, all five wrist taps are felt at the wrist in the expected manner. The brain obviously cannot "know" about a tap at the elbow until after it happens. Perhaps, one might speculate, the brain delays the conscious experience until after all the taps have been "received" and then, somewhere upstream of the seat of consciousness (whatever that is), revises the data to fit a theory of motion, and sends the edited version on to consciousness. But would the brain always delay response to one tap in case more came? If not, how does it "know" when to delay? Ce "Referral backwards in time." Since Penfield and Jasper (1954) it has been known that direct electrical stimulation of locations on the somatosensory cortex can induce sensations on corresponding parts of the body. For instance, stimulation of a point on the left somatosensory 186 BEHAVIORAL AND BRAIN SCIENCES (1992) 15:2 Dennett & Kinsbourne: Time and the observer cortex, can produce the sensation of a brief tingle in the subject's right hand. Libet compared the time course of such cortically induced tingles to similar sensations proTM duced in the more usual way, by applying a brief electrical pulse to the hand itself (Libet 1965; 1981; 1982; 1985a; Libet et al. 1979; see also Churchland 1981a; 1981b; Dennett 1979; Honderich 1984; Popper & Eccles 1977). He argued that although in each case it took considerable time (approximately 500 msec) to achieve "neuronal adequacy" (the stage at which 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." Most strikingly, Libet reported instances in which a subject's left cortex was stimulated before his left hand was stimulated, something one would tend to expect to 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." Even in cases of simultaneous stimulation, one might have thought, the left-hand tingle should be felt second, because of the additional distance (close to a meter) nerve impulses from the left hand must travel to the brain. Libet interprets his results as raising a serious challenge to materialism: "A dissociation between the timings of the corresponding 'mental' and 'physical' events would seem to raise serious though not insurmountable difficulties for the . . . theory ofpsychoneural identity" (1979, p. 222). According to Eccles, this challenge cannot be met: 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 & Eccles 1977, p. 364) BB Subjecfiwe delay of consciousness of intention* In other experiments, Libet asked subjects to make "spontaneous" decisions to flex one hand at the wrist while noting the position of a revolving spot (the "second hand" on a clock, in effect) at the precise time they formed the intention (Libet 1985a; 1987; 1989a; see also the accompanying commentaries). Subjects' reports of these subjective simultaneities were then plotted against the timing of relevant electrophysiological events in their brains. Libet found evidence that these "conscious decisions" lagged between 350 and 400 msec behind the onset of "readiness potentials" he was able to record from scalp electrodes, which, he claims, tap the neural events that determine the voluntary actions performed. He concludes that "cerebral initiation of a spontaneous voluntary act begins unconsciously" (1985a, p. 529). That one's consciousness might lag behind the brain processes that control one's body seems to some an unsettling and even depressing prospect, ruling out a real (as opposed to illusory) "executive role" for "the conscious self." (See the discussions by many commentators in BBS: Eccles 1985; Mortenson 1985; Van Gulick 1985; and in Pagels 1988, pp. 233ff; and Calvin 1990, pp. 80-81. But see, for a view close to ours, Hamad 1982.) In none of these cases would there be prima facie evidence of any anomaly were we to forego the opportunity to record the subjects' verbal reports of their experiences and subject them to semantic analysis. No sounds appear to issue from heads before lips move, nor do hands move before the brain events that purportedly cause them, nor do events occur in the cortex in advance of the stimuli that are held to be their source. Viewed strictly as the internal and external behavior of a biologically implemented control system for a body, the events observed and clocked in the experiments mentioned exhibit no apparent violations of everyday mechanical causation — of the sort to which Galilean/Newtonian physics provides the standard approximate model. Libet said it first: "It is important to realize that these subjective referrals and corrections are apparently taking place at the level of the mental 'sphere'; they are not apparent, as such, in the activities at neural levels" (1982, p. 241). Put more neutrally (pending clarification of what Libet means by the "mental 'sphere'"), only through the subjects' verbalizations about their subjective experiences do we gain access to a perspective from which the anomalies can appear. Once their verbalizations (including communicative button-pushes, etc.; Dennett 1982), are interpreted as a sequence of speech acts, their content yields a time series, the subjective sequence of the stream of consciousness. One can then attempt to put this series into registration with another time series, the objective sequence of observed events in the environment and in the nervous system. It is the apparent failures of registration, holding constant the assumption that causes precede their effects, that constitute the supposed anomalies (cf. Hoy 1982). One could, then, "make the problems disappear" by simply refusing to take introspective reports seriously. Although some hearty behaviorists may cling comfortably to the abstemious principle, "Eschew content!" (Dennett 1978), the rest of us prefer to^accept the challenge to make sense of what Libet calls "a primary phenomenological aspect of our human existence in relation to brain function" (1985a, p. 534). The reports by subjects about their different experiences . . . were not theoretical constructs but empirical observations. . . . The method of introspection may have its limitations, but it can be used appropriately within the framework of natural science, and it is absolutely essential if one is trying to get some experimental data on the mind-brain problem. (Libet 1987, p. 785) In each example an apparent dislocation in time threatens the prima facie plausible thesis that our conscious perceptions are caused by events in our nervous systems, and our conscious acts, in turn, cause events in our nervous systems that control our bodily acts. To first appearances, the anomalous phenomena show that these two standard causal links cannot be sustained unless we abandon a foundational some would say a logically necessary principle: Causes precede their effects. It seems that in one case (subjective delay of awareness of intention), our conscious intentions occur too late to be the causes of their bodily expressions or implementations, and in the other cases, percepts occur too early to have been caused by their stimuli. The vertiginous alternative, that something in the brain (or "conscious self") can "play tricks with time" by "projecting" mental events backwards in time, would require us to abandon the foundational principle that causes precede their effects. BEHAVIORAL AND BRAIN SCIENCES (1992) 15:2 187 Dennett & Kinsbourne: Time and the observer There is a widespread conviction that no such revolutionary consequence follows from any of these phenomena, a conviction we share. But some of the influential arguments that have been offered in support of this conviction persist in a commitment to the erroneous presuppositions that made the phenomena appear anomalous in the first place. These presuppositions are all the more insidious because although in their overt, blatant forms they are roundly disowned by one and all, they creep unnoticed back into place, distorting analysis and blinding theory-builders to other explanations. action: Diagnosing the tempting 2.1 • Th® representation of temporal properties wersus the temporal properties of representations. The brain, as the control system responsible for solving a body's real-time problems of interaction with the environment, is under significant time pressure. It must often arrange to modulate its output in light of its input within a time window that leaves no slack for delays. In fact, many acts can be only ballistically initiated; there is no time for feedback to adjust the control signals. Other tasks, such as speech perception, would be beyond the physical limits of the brain's machinery if they did not use ingenious anticipatory strategies that feed on redundancies in the input (Libermann 1970). How, then, does the brain keep track of the temporal information it manifestly needs? Consider the following problem: Because the toe-brain distance is much greater than the hip-brain distance, or the shoulder-brain distance or the forehead-brain distance, stimuli delivered simultaneously at these different sites will arrive at Headquarters in staggered succession, if travel-speed is constant along all paths. How (one might be tempted to ask) does the brain "ensure central simultaneity of representation for distally simultaneous stimuli"? This encourages one to hypothesize some "delay loop" mechanism that could store the early arrivers until they could be put "in synch" with the latecomers, but this is a mistake. The brain should not solve this problem, for an obvious engineering reason: It squanders precious time by committing the full range of operations to a "worst case" schedule. Why should important signals from the forehead (for instance) dawdle in the anteroom just because there might someday be an occasion when concurrent signals from the toes need to be compared to (or "bound to") them? The brain sometimes uses "buffer memories" to cushion the interface between its internal processes and the asynchronous outside world (Neisser 1967; Newell et al. 1989; Sperling 1960), but there are also ways for the brain to use the temporal information it needs without the delays required for imposing a master synchrony. The basic design principle is well illustrated in an example in which a comparable problem is confronted and (largely) solved, though on a vastly different temporal and spatial scale. Consider the communication difficulties faced by the far-flung British Empire before the advent of radio and telegraph, as illustrated by the Battle of New Orleans. On January 8, 1815, 15 days after the truce was signed in Belgium, more than a thousand British soldiers were killed in this needless battle. We can use this debacle to see how the system worked. Suppose on Day 1 the treaty is signed in Belgium, with the news sent by land and sea to America, India, Africa. On Day 15 the battle is fought in New Orleans, and news of the defeat is sent by land and sea to England, India, and so on. On Day 20, too late, the news of the treaty (and the order to surrender) arrives in New Orleans. On Day 35, let's suppose, the news of the defeat arrives in Calcutta, but the news of the treaty doesn't arrive there until Day 40 (via a slow overland route). To the commander-in-chief in Calcutta, the battle would "seem" to have been fought before the treaty was signed were it not for the practice of dating letters, which permits him to make the necessary correction. These communicators solved their problems of communicating information about time by embedding representations of the relevant time information in the content of their signals, so that the arrival time of the signals themselves was strictly irrelevant to the information they carried. A date written at the head of a letter (or a dated postmark on the envelope) gives the recipient information about when it was sent, information that survives any delay in arrival. This distinction between time represented (by the postmark) and time of representing (the day the letter arrives) is an instance of a familiar distinction between content and vehicle, and although the details of this particular solution are not available to the brain's communicators (because they don't "know the date" when they send their messages), the general principle of the content/vehicle distinction is relevant to information-processing models of the brain in ways that have not been well appreciated. In general, we must distinguish features of representings from the features of representeds (Neumann 1990); someone can shout "softly, on tiptoe" at the top of his lungs, there are gigantic pictures of microscopic objects and oil paintings of artists making charcoal sketches. The top sentence of a written description of a standing man need not describe his head, nor the bottom sentence his feet. To suppose otherwise is confusedly to superimpose two different spaces: The representing space and the represented space. The same applies to time. Consider the spoken phrase, "a bright, brief flash of red light." The beginning of if is "a bright" and the end of it is "red light." Those portions of that speech event are not themselves representations of onsets or terminations of a brief red flash (c£ Efron 1967, p. 714). No informing event in the nervous system can have zero duration (any more than it can have zero spatial extent), so it has an onset and termination separated by some amount of time. If it represents an event in experience, then the event it represents must itself have nonzero duration, an onset, a middle, and a termination. But there is no reason to suppose that the beginning of the representing represents the beginning of the represented. Similarly, the representing by the brain of "A before B" does not have to be accomplished by first: a representing of A,