REVIEW OF ANTONIO R. DAMASIO, Descartes' Error: Emotion, Reason, and the Human Brain, 1994
in the Times Literary Supplement, August 25, 1995, pp. 3-4.
Daniel C. Dennett
The legacy of René Descartes' notorious dualism of mind and body extends far beyond academia into everyday thinking: "These athletes are prepared both mentally and physically," and "There's nothing wrong with your body--it's all in your mind." Even among those of us who have battled Descartes' vision, there has been a powerful tendency to treat the mind (that is to say, the brain) as the body's boss, the pilot of the ship. Falling in with this standard way of thinking, we ignore an important alternative: viewing the brain (and hence the mind) as one organ among many, a relatively recent usurper of control, whose functions cannot properly be understood until we see it not as the boss, but as just one more somewhat fractious servant, working to further the interests of the body that shelters and fuels it, and gives its activities meaning. This historical or evolutionary perspective reminds me of the change that has come over Oxford in the thirty years since I was a student there. It used to be that the dons were in charge, while the bursars and other bureaucrats, right up to the Vice Chancellor, acted under their guidance and at their behest. Nowadays the dons, like their counterparts on American university faculties, are more clearly in the role of employees hired by a central Administration, but from where, finally, does the University get its meaning? In evolutionary history, a similar change has crept over the administration of our bodies. Where resides the "I" who is in charge of my body? In his wonderfully written book, Antonio Damasio seeks to restore our appreciation for the perspective of the body, and the shared balance of powers from which we emerge as conscious persons.
There has been something of a flood of books about the mind and consciousness by neuroscientists and psychologists in the last three or four years, often informative and clearly written, but seldom offering much beyond textbook fare. Damasio, one of the world's leading researchers in neuroscience and head of the department of neurology at the University of Iowa College of Medicine, in Iowa City, has produced one of the exceptions. There are not many factual novelties here for those who have been staying abreast of this literature, but Damasio has woven some familiar if undervalued facts together into a vision of the brain and its parts that really makes sense, biologically, psychologically, and philosophically. Damasio's vision is in itself not entirely novel--its major elements can be discerned in Aristotle, in Nietzsche, and most recently in Nicholas Humphrey's A History of the Mind--but under Damasio's boldly constructed umbrella of neuroanatomical details, these elements join to become not just compelling, but retrospectively obvious, provoking the theorist's ultimate accolade: "Now why didn't I think of that?"
Long before there were telephones and radios, there was the postal service, reliably if rather slowly transporting physical packages of valuable information around the world. And long before there were nervous systems in organisms, bodies relied on a low-tech postal system of sorts, the bloodstream, reliably if rather slowly transporting hormones and other valuable packages of information around to where they were needed for control and self-maintenance. The bloodstream carries goods and waste, but it has also been, since the early days, an information highway. Next came simple nervous systems--ancestors of the autonomic nervous system--capable of swifter and more efficient information transmission, but still devoted, in the main, to internal affairs. An autonomic nervous system is not a "mind" at all, but a control system more along the lines of the organization of a plant, preserving the basic integrity of the living system. Aristotle called such an organization a "vegetative soul." Damasio points out that in evolutionary history, organisms must have begun with a concern only for their internal problems and prospects, eventually graduating to a concern for proximal problems and prospects at their boundaries, before advancing to the concern for, and cognitive appreciation of, ever more distal problems or prospects.
All this is "obvious" but its major implication is under-appreciated: "Nature appears to have built the apparatus of rationality not just on top of the apparatus of biological regulation, but also from it and with it." (p.128.) Failure to see this, Damasio says, is Descartes' error. Far from there being a separation, sharp or ragged, between mind and body, mind cannot exist or operate at all without body. The idea that the body's needs set the pace and indirectly drive the brain's decisions is not new. When Damasio says that the older, blood-based systems intertwine with the "more modern and plastic ones" in the nervous system, via a host of feedback loops, and that thereby "the goodness and badness of situations is regularly signaled" to the nervous system, this idea occupies much the same explanatory niche as Skinner's ideas about how innate mechanisms reinforced appropriate stimulus-response pairings, for instance, but Damasio makes a more interesting proposal out of it. In particular, he shows how this intimate body-involvement plays important roles in explaining some of the juicier and more mysterious facts of "phenomenology."
As organisms acquired greater complexity, 'brain-caused' actions require more intermediate processing. Other neurons were interpolated between the stimulus neuron and the response neuron, and varied parallel circuits were thus set up, but it did not follow that the organisms with that more complicated brain necessarily had a mind. Brains can have many intervening steps in the circuits mediating between stimulus and response, and still have no mind, if they do not meet an essential condition: the ability to display images internally and to order those images in a process called thought. (p89).
Who or what is the audience for this "display" of "images"? Not a Cartesian ego or self, isolated in some central module--the dread Cartesian Theater--and overburdened with powers and responsibilities, but a self distributed throughout the body, a clear descendant of the Aristotelian vegetative soul.
Of what are these "images" composed? "Images are based directly on those neural representations, and only on those, which are organized topographically and which occur in early sensory cortices."[italics in original p.98.] These are, in vision, the "retinotopic maps" that preserve features of the geometry of the retinal image, and more generally the "body image" patterns of stimulation that similarly preserve a map of the whole body. These neural representations exploit the geometry of the map (to some extent) to encourage the evocation of the patterns that matter, when they matter, and because they matter to the body. This is a strong claim, which might have to be watered down later, but let's understand it in the strong sense first. One of its implications is that "imageless thought," a perennially discussed possibility-in-principle is impossible in fact, for us. In us, Damasio claims, all thought is grounded in these body-representing neural structures, and from this they gain the power to move us in ways that "pure thought" could not. Descartes imagined that pure rational thought had its own dynamic, divorced from the body; once decisions had been made, thought somehow reached out of the mind to grab the body's controls and make things happen. In Damasio's vastly improved vision, even the highest flights of reason are set in motion, and kept in appropriate motion, by interactions with the rest of the body. Another implication is that human reasoning is never a matter of rule-governed manipulation of "pure" propositions (the logic-class model of reasoning), but rather is always imagistic--even in those rare cases of sophisticated deduction in which the images are of logical formulae being manipulated. This is not a new idea--Philip Johnson-Laird and others have combatted logicist models of reasoning for years--but it is a new source of support and explanation.
Moreover, according to Damasio, not all exploitation of such map-like representations amounts to thought: "In other words, if our brains would simply generate fine topographically organized representations and do nothing else with those representations, I doubt we would ever be conscious of them as images." [p99] What would be missing is "the neural basis for the self" with which these images must be "correlated."
And how is that fine trick accomplished? In addition to the basic images (which Damasio carefully distinguishes from "facsimile" images--literal pictures in the head), there are "dispositional representations," specialist agencies that set off chains of reaction that reach deep down into the body's accumulated experience, thereby calling to mind (you might say) not only further images of reliably appropriate content, but "somatic markers," emotional states that color everything with specific varieties of urgency and calm, rendering various further thoughts relatively unthinkable, while driving others into attention--after all, "The allocation and maintenance of attention and working memory do not happen by miracle." [p.198]The all-too-wise Cartesian homunculus is thus relieved of the burden of comprehending the full import of every image, and the task of directing attention where it is needed is distributed around the body, creating what Douglas Hofstadter calls "active symbols" that can compete for attention with each other, needing no boss or traffic cop to determine the marching order. Consider, Damasio notes, the "sheer will power" with which I sometimes set aside one inviting topic of thought in order to concentrate on something "I" deem more pressing--what on earth could that be? It could be the net effect of somatic markers, modulated by prefrontal (ventromedial) and limbic structures, influencing this allocation "within the dorsolateral sector" of the frontal cortices. (Again, this claim might be too strong, but let's give it a workout.)
None of these anatomically identifiable "convergence zones" is a Cartesian Theater because none does more than just a fraction of the cognitive work.
Convergence zones located in the prefrontal cortices are thus the repository of dispositional representations for the appropriately categorized and unique contingencies of our life experience. . . . . (Remember that, neurally speaking, the reconstructions do not occur in prefrontal cortices, but rather in varied early sensory cortices where topographically organized representations can be formed.) [p182]
The frontal cortex has long been recognized to play a marked role in motivation and control, but too often it looms up through the mists of theory as the seat of the ego itself, the ultimate arbiter, the fons et origo of value (e.g., in Gerald Edelman's work), instead of as an important mediating agent between ancient bases of selfhood and their more modern components. The frontal region adds editorial commentary, applause or warning labels, and thereby calls up other ideas, not comprehending them all, but only semi-comprehending them. The comprehension of the whole agent is the emergent product of all the activity.
Some of the decision-making in us is not so heavily worked over, but swiftly accomplished by "covert mechanisms" [p185] directly responding to somatic markers. In these cases, we make relatively unthinking and "instinctive" decisions, and this is the sole means of decision-making in non-human animals, Damasio claims. It is our capacity for ever higher levels of meta-reflection that distinguish our selves from the more rudimentary biological selves (or vegetative souls) of other species. To come up with any model of the human self is a tall order, and Damasio's model is both psychologically plausible and complex and detailed enough to be testable. This is wonderful bold theorizing, a tour de force of sheer reflective imagination, generous-minded reading of ideas from other research traditions, and self-criticism. Many of its details will survive intact, in my opinion, but it may go off the rails just a bit at one point, in Damasio's discussion of what he calls the "meta-self." We don't need to posit a separate (or autonomous) meta-self, I think. Let me attempt a friendly amendment: The reactivity cascade Damasio describes either satisfies all the "epistemic hunger" of all the active agencies, or creates new hungry agencies--ad lib (but not ad infinitum), whose hunger is either satisfied, or not, and so forth. If all the hunger is satisfied, no alarms ring through the system and life goes on. Otherwise, the cascade continues, indefinitely. As Damasio himself says, "The dispositional representation I have in mind is neither created nor perceived by a homunculus." [p242]
Taking a woebegone precept from Bill Clinton and putting it to a better use, we might call this the Don't ask; don't tell model of reflective consciousness. That is, unless the organization is provoked into a further inquiry by some unsatisfied agency, it swiftly proceeds on its current control tasks, not bothering to create, for the nonce, any more meta-levels than are required to deal with the current problems. This theme, by the way, is also developed in Artificial Intelligence by Allen Newell in his Unified Theories of Cognition. Newell and his colleagues designed a cognitive architecture called SOAR, which builds "problem spaces" only when it can't solve its current problem with current resources. The "productions" of SOAR (or production systems more generally) are close kin to Damasio's "dispositional representations," but even closer kin can be found in the models developed by Douglas Hofstadter and his group at Indiana (see, e.g. Douglas Hofstadter, Fluid Concepts and Creative Analogies). Damasio's emphasis on the distinction between imagistic and dispositional representations finds its parallels in the "scratchpad" and "workspace" and "slipnet" and other purely functional (that is, entirely non-anatomical) categories postulated by this family of models. As usual, it is reassuring to find thinkers arriving, from such different precincts, using such different tools, at much the same ideas (with a little friendly amendment from me). We may be seeing some of the first bridges thrown across the huge chasm of ignorance between psychology and neuroanatomy.
No doubt the bulwark of skepticism will remain unshaken in the minds of many. How could any such model of neural activity add up to a theory of conscious thought? What about "qualia"? Damasio does address the issue, eschewing that ill-favored term, I am happy to say, and speaking instead of subjectivity.
Think of viewing a favorite landscape. . . . As knowledge pertinent to the landscape is activated internally from dispositional representations in those various brain areas, the rest of the body participates in the process. Sooner or later, the viscera are made to react to the images you are seeing, and to the images your memory is generating internally, relative to what you see . . . The organism actively modifies itself so that the interfacing can take place as well as possible. [p.224-25].
Damasio compares his view to that of Francis Crick: "Crick has not overlooked the problem of subjectivity altogether. Rather, he has decided not to consider it at this time since he doubts it can be approached experimentally." [p.243] But by postponing indefinitely the hard question ("And then what happens?"), Crick, like most neuroscientists, leaves subjectivity--"qualia"--utterly mysterious. Damasio sees that the only way to explain the presumptive qualia is, once again, to distribute their effects and powers through the body, instead of concentrating them in some imaginary dazzle in the eyes of the Cartesian homunculus. His good idea of "representing the outside world in terms of modifications it causes in the body proper" (p.230) is also the central proposal of Nicholas Humphrey's recent account of subjectivity (which Damasio encountered after drafting his book, and cites as an anticipation). Damasio's version, by going into more anatomical detail, removes some of the air of speculative guess-work that fueled skepticism about Humphrey's claims. Much the same remark could be made, I readily grant, about Damasio's model in relation to my own model of consciousness. Damasio says he is "fairly certain" that his "device for generating subjectivity" is not "Dennett's virtual machine" (in Consciousness Explained), but it also does not contradict it. With a variety of minor amendments to both models, I see no reason not to join forces. In my book I deliberately eschewed anatomical speculation that wasn't absolutely required to set out my theory, but I've always been eager to add details whenever they get properly motivated.
This is a time for bold attempts, not worrying overmuch about proving each conjecture along the way, but rather getting enough of a story clearly out on the table to suggest tests, and the inevitable further refinements. It is time for tentative model-building, in other words, without undue anxiety about overstating the case at the outset. There are hundreds (or thousands) of bits lying around that need to be incorporated into a "working model" of a whole human agent, and just finding one plausible (and ultimately testable) model of a whole agent is an extremely demanding task. It requires a mixture of global vision and detailed knowledge, and lots of imagination. Damasio has bravely provided a pretty good--maybe a very good--model, and some of the most fascinating parts of the book are his accounts of the recent experiments conducted in his lab, involving patients with damage to the frontal regions that figure so prominently in his theory. When such patients are presented with a slide show that includes graphic pictures of sex or violence, for instance, they can identify them and describe their horrible details normally, but they show none of the emotional responses that are irresistible in normal people. Far from being demented, these patients can be acutely aware of this missing ingredient in their mental lives, and yet its absence is not just an upsetting gap or blank--like losing all feeling in a limb, or losing one's sense of smell--but a huge disability, preventing them from leading safe and successful lives. As Damasio slyly points out, these patients are the very epitome of the cool-headed, passionless thinkers philosophy has typically encouraged as the ideal, and yet that very lack of emotional coloring renders them pathetically ill-equipped for the rough-and-tumble of real world time-pressured decision-making.
That acknowledged, it is important to add that Damasio is not "reducing" human reason, human judgment, human art and genius and moral insight, to the ebb and flow of hormones and neuromodulators. He is providing a model of the mechanisms--and barring miracles, there have to be mechanisms--that subserve and implement those precious human activities and propensities. There is still as much room as ever (perhaps more, now that the mists have parted a little) for praise and blame, for desert and self-criticism and wonder. These gifts never could be made to reside in some precious pearl of Cartesian mind-stuff, so the sooner we find out how our bodies make room for them, the better.
As Nicholas Humphrey has pointed out (in letters to me and Damasio), Friedrich Nietzsche saw all this long ago, and put the case with characteristic brio, in Thus Spake Zarathustra (in the section aptly entitled "On the Despisers of the Body"):
"Body am I, and soul"--thus speaks the child. And why should one not speak like children? But the awakened and knowing say: body am I entirely, and nothing else; and soul is only a word for something about the body. The body is a great reason, a plurality with one sense, a war and a peace, a herd and a shepherd. An instrument of your body is also your little reason, my brother, which you call "spirit"--a little instrument and toy of your great reason. . . . Behind your thoughts and feelings, my brother, there stands a mighty ruler, an unknown sage--whose name is self. In your body he dwells; he is your body. There is more reason in your body than in your best wisdom. [Kauffman translation, 1954, p.146][3300 words]