Buskell, Andrew

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  Andrew Buskell Book review: Andy Clark // surfing uncertainty: prediction, action, and the embodied brain  Article (Published version) (Non-refereed)     Original citation: Buskell, Andrew (2017) Book review: Andy Clark // surfing uncertainty: prediction, action, and the embodied brain. British Journal for the Philosophy of Science - Review of Books . ISSN 0007-0882  © 2017 The Author  This version available at: http://eprints.lse.ac.uk/73659/   Available in LSE Research Online: April 2017  LSE has developed LSE Research Online so that users may access research output of the School. Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Users may download and/or print one copy of any article(s) in LSE Research Online to facilitate their private study or for non-commercial research. You may not engage in further distribution of the material or use it for any profit-making activities or any commercial gain. You may freely distribute the URL (http://eprints.lse.ac.uk) of the LSE Research Online website.  Andy Clark // Surfing Uncertainty: Prediction, Action, andthe Embodied Brain bjpsbooks.wordpress.com /2017/01/31/andy-clark-surfing-uncertainty-prediction-action-and-the-embodied-brain/View all posts by bjpsbooksReviewed by Andrew BuskellSurfing Uncertainty: Prediction, Action, and the Embodied BrainAndy ClarkOxford: Oxford University Press, 2016, £20 (hardback)ISBN 9780190217013I have a vivid memory from my undergraduate degree in psychology: a short video, no longer than five secondslong, showing the characteristic ‘pinwheel’ activation of orientation-sensitive cells in the primary visual cortex.These cells (clumped into ‘columns’) respond differentially to the orientation of light in the visual field. In the videoI watched, this responsiveness was rendered in dramatic fashion: responding to a clock-wise rotating stimuli, theactivation pattern of the cells rotated in near perfect synchrony.I suspect this video is typical of those shown to undergraduates. Typical too, I would wager, is the philosophicalpicture wedded to it: perception involves the detection of external stimuli and the successive processing andenrichment of that stimuli in service of producing a rich internal representation of the outside world.According to Andy Clark, this philosophical picture is misleading. In Surfing Uncertainty: Prediction, Action, andthe Embodied Brain, Clark aims to replace this picture of detection, enrichment, and rich internal representation.His alternative picture is one based upon generative models, precision-weighting, and the detection ofprediction-error. While the traditional picture is bottom-up and employs a strategy of building a model of the worldthat lags just behind the world in the here-and-now, Clark’s alternative is almost the complete inverse; it holdsthat cognition involves top-down models that make guesses as to how the states of the world are likely to unfold,and these predictions guide the (generally, sub-personal) selection of percept, sensory orientation, and action.I think Clark is right to identify the picture presented in the book as a ‘mid-level organizational sketch’ (p. 2). Itprovides a general and abstract mechanistic characterisation of the function and organization of the nervoussystem. The broad contours of this sketch hold that the brain is in the business of acquiring and tuning a modelthat generates predictions about the temporally fluctuating distal causes of sensory stimulation. Filling in thisorganizational sketch is the work of the first third of the book—applying it to the wide range of psychological andphilosophical issues in psychology, philosophy of mind, and beyond occupies the latter two thirds.Part one provides the reader with more detail on Clark’s ‘organizational sketch’; what he comes to callhierarchical action-oriented predictive processing (hereafter, PP). As stated above, PP is a characterization ofthe organization and function of the nervous system. It holds that cognitive systems can be organized intohierarchical levels, and that higher levels of the hierarchy are in the business of predicting the incoming stimulifrom lower levels. Errors resulting from mismatches between stimuli and prediction are fed back to the higherlevels to revise future guesses. This view, with roots in the work of Karl Friston, Geoffrey Hinton, David Knill, andAlexandre Pouget, turns the traditional picture on its head. Instead of a rich internal representation of the worldthat must be continually updated, Clark’s picture posits that the nervous system realizes a ‘generative model’,one that produces hypotheses about the spatiotemporal structure of sensory input. This generative model in turnis the result of an extended process of Bayesian inference, where initial guesses as to how the world isorganized are inferred on-the-go as individuals develop, and which are tuned and tweaked as individuals engagein the dynamic flow of the world.If I understand Clark’s account correctly, what agents actually experience are the hypotheses produced by the1/4generative model. Yet despite the fact that experiences result or are realized by inner structures, one should notthink of this generative model in terms of representations that ‘mirror’ the world. This would miss the inherentstrangeness of the generative model as compared to traditional, folky characterizations of representationalcontent. To give something of a caricature, a folky characterization holds that early perceptual processes areinvolved in something like feature placing, with representational content increasing in detail and richness untilsomething like a representational duplicate of the world has been achieved, replete with facsimiles of the entitiesand properties out there in the world. On Clark’s account, however, movement up the representational hierarchybrings with it increasing temporal and spatial scope over sensory stimuli. At the higher levels of this hierarchy,representations consist in probability distributions over temporally extended trajectories of sensory stimulation.This is a radical departure from a picture of representational content that corresponds to or mirrors states ofaffairs of the world.Chapter two adds in a crucial component of Clark’s project: precision-weighting. For Clark, ‘we are constantlyengaged in attempts to predict precision, that is, to predict the context-varying reliability of our own sensoryprediction error’ (p. 58). Developed with increasing precision throughout the book (notably in Chapters 4, 5, and7) the account of precision-weighting the reader is given is one where variable uncertainty leads to savvysampling of information-rich patches of the world, particularly those that can help to determine the context thatone is in, or the right action to take. In Clark’s terminology, precision-weighting modulates the influence of top-down priors relative to bottom-up stimuli. Normal (that is, non-pathological) cognitive and behaviouralengagement with the world comes to rest on precision-weighting achieving the right kind of ‘balance’ betweenpredictions and stimuli.Despite Clark grouping Chapter 3 in with the first part of the book, I think it sits more easily with the second,thematic part of the book that extends to Chapter 7. In part two, Clark interrogates clumps (there might be nobetter word here) of psychological, neuroscientific, psychopathological, and cognitive phenomena. Theseclumps are often broad, involving surveys over a huge range of material and subject matters. In discussing eachof these clumps, Clark argues cogently and forcefully that the PP framework provides a powerful means ofgetting at the empirical facts of the matter.Because of the large and disparate amount of material covered in Chapters 3 through to 7, it would be foolish totry give a full description of what is covered therein, let alone a satisfactory analysis. Instead, I here summarizethe general phenomena discussed in each chapter, which should give the reader some idea of what is in storewhen they pick up the book. Chapter 3 discusses a ‘cognitive package deal’, with PP taken to give a neat andtidy account as to how episodic memory, imagination, and dreaming could emerge together. Chapter 4 looks atthe integration of PP with action, planning, and the control of behaviour. Chapter 5 examines the nature of mirrorneurons, proprioceptive information, off-line rehearsal of action, and the role of context and context-detection.Chapter 6 is an examination of the debate between empiricist and nativists about cognitive architecture, andlooks at the way in which a PP architecture qua an empirical Bayes approach can illuminate these debates, aswell as the nature and selection of environmental affordances. Finally, Chapter 7 reflects on the nature ofneuropathologies such a schizophrenia, autism, and depersonalization disorder. As stated above, in each ofthese chapters, Clark labours to show that the PP framework not only captures the phenomena discussed in theliterature, but makes new predictions, solves old problems, and ultimately provides a more empirically fruitfulmeans of getting at cognitive phenomena.Looking at the wide range of material discussed, and the kind of argument that Clark is attempting, it shouldcome as no surprise to note that the most frequently used phrase in the book is ‘The upshot is…’. Indeed, to mymind, Chapters 3 through to 7 can be seen as providing an extended inference to the best explanation, withClark articulating the empirical benefits that come along when one adopts the PP framework. Key among thesebenefits is the way in which the PP framework can provide a unifying and synthesizing framework forunderstanding the nervous system and cognitive phenomena.The last two chapters make up the final part of the book. While there is a great deal of empirical contentdiscussed in these chapters, it seems to me that they are more accurately characterized as providing a pictureof human cognition and behaviour in all its richness—what Peter Godfrey-Smith has called a ‘philosophy ofnature’. In Chapter 8, Clark considers the ‘dynamic instability’ of human hierarchical PP as a means of capturing2/4phenomena such as curiosity and neophilia, as well as dissolving worries that the PP will lead one to hide in a‘darkened room’. The last chapter of the book, Chapter 9, situates the cognitive agent in the richness of the widersociocultural milieu, bringing in concepts of self-organization, creativity, scaffolding, niche-construction,language, and joint-organization to show how PP can be integrated with contemporary work in cultural evolution,enactivism, and embodied cognition.What I hope comes through from the reflections above is a recognition of the argumentative strategy of the book.The argument is cumulative: part one introduces the pieces of machinery that are deployed in part two andthree. In these later parts, similar arguments and strategies are deployed again and again to erode support forthe ‘enrichment’, or ‘bottom-up’ conception of mentality and cognition, and to cement the empirical merits of thePP picture. By the end of part three, we have been provided with a comprehensive and holistic picture, one thatcan accommodate, relate, and explain a wealth of cognitive, neuroscientific, and social phenomena.As is always the case with scholarly monographs, individuals will have wished that some issues were discussedin more detail, or analysed in greater depth. For what it is worth, I would have like to have further discussion ofthe ‘hierarchy’ in ‘hierarchical action-oriented predictive processing’, as we seem to have been given verydifferent characterisations of what this hierarchy consists in.Above, I characterized cognitive processing—‘ascending the representational hierarchy’—in terms ofrepresentations or predictions of increasing spatiotemporal scope. This is a characterization endorsed severaltimes throughout the book (pp. 111, 158, 184). But as the book progresses, Clark introduces alternativecharacterizations that bring in distinct elements. Notably, in Chapter 5, Clark puts the emphasis on context, andsuggests that as representations move up in the representational hierarchy, they represent increasingly sketchy,but high-level, ‘gists’ of scenarios. This hierarchy tops-off when one reaches a background ‘mindset’, whichprovides the ‘baseline sets of expectations that are themselves already active when we process even theroughest, coarsest sets of sensory cues from the external (or indeed the internal) environment’ (p. 166). Further,in later chapters of the book, we are introduced to the intriguing notion of a ‘hyperprior’ (pp. 174–5, 188), whichthe reader is told embodies ‘systemic expectations concerning very abstract (at times almost “Kantian”) featuresof the world’ (p. 174). Clark uses this characterization (at least) to make sense of the way in which, despite theprobabilistic nature of our generative model, we always see the world as being in one determinate state oranother.To my mind, these three characterizations describe very distinct kinds of models, and different pictures as towhat it means to ‘move up’ the representational hierarchy. Spatiotemporal scope is not (necessarily) the same asgist or context, nor are these (necessarily) the same as invariant features of experience or behaviour. Perhapsthese features of high-level representations are compatible, or maybe even partially overlapping—but this neednot be the case.I suspect this represents a small if non-trivial conceptual worry for the PP account Clark develops. A morepressing issue concerns those that will deny at the outset the kind of picture that Clark attempts to put forward.Those who are committed to something like ‘bottom-up’ approaches to cognition will no doubt be able to craftclever hypotheses in order to save the phenomena. Clark even considers several means by which such craftyhypotheses have already been deployed to explain tricky aspects of action control (notably, efference-copyaccounts, covered in Chapter 4).One useful means of organizing some of the arguments of Clark’s book, then, might be to bring in what GeraldHolton ([1975], p. 330) called ‘themata’. For Holton, such themata represent ‘early, unshakable commitments’ toalternate conceptual frameworks. Despite the fact that such frameworks appeal to antithetical ‘thematic concepts’(Holton’s examples, from physics, include dyads like ‘continuum’ and ‘discreteness’), there is plenty of scope forempirical disagreement. As a matter of fact, as Holton notes, it is often the case that in ‘the scientists’ own publicpresentation of their work, and during any ensuing scientific controversy, these [thematic] elements are usuallynot explicitly at issue’. Indeed, lest scientists risk being called philosophers, the focus remains on the adequacyof theories to accommodate and explain empirical phenomena.It is useful to have Holton’s themata in the back of one’s mind when reading Clark’s book. For while the3/4overarching message is that it is helpful to switch one’s early, unshakeable commitments—from a ‘bottom-up’picture of enrichment to a ‘top-down’ picture of hierarchical predictive processing—much of the substance of thebook is an engagement with cutting-edge empirical research from a huge variety of sources. And this makessense.  Themata, as Holton characterizes them, are not hypotheses that can be falsified. They are somethingmuch more fundamental, representing perspectives or frames as to how the world is organized. Nonetheless, forClark, this ‘top-down’ picture seems to provide a greater and more fruitful empirical grasp on cognitive andneuroscientific phenomena, one that brings with it a comprehensive and unifying perspective on what the brainis doing.The focus on empirical details is effective in showing the wide-ranging scope and predictive power of Clark’saccount—but it is likely to leave as many questions unanswered as answered. Proponents of various positionswithin experimental psychology, neuroscience, and embodied cognition (to name just a few) are likely to feel thatissues around mirror neurons, context, skills, and imitation are treated far too hastily, and that this might bereason enough to reject Clark’s picture. Philosophers might also think that important issues are not adequatelydiscussed. Mentions of folk psychology, disjunctivism, realism, and the nature of representation are brief, andoften find their most interesting arguments hidden away in the book’s many footnotes. As a result, philosopherstoo might question whether we’ve really been given a ‘knock-down’ argument in favour of PP.Such knee-jerk reactions would be unfortunate. Clark’s book should not be taken as a definitive account of allthe phenomena he discusses, and it will always be the case in a book like this that researchers will feel that theirparticular research topics could have been given more space and more comprehensive discussion.Let me conclude with two final remarks. The first is that it is important to recognize the scope and audacity ofClark’s book. It synthesizes an absolutely massive amount of material—both empirical and philosophical—andmanages to present this material in an illuminating, coherent, and compelling manner. Of course, individuals willdisagree on the extent to which this synthesizing vision is successful, as well as on the details of the picture.This brings me to my second point. Like some of his other books (notably, the classic Microcognition ([1989]) andthe well-known Being There ([1996])), this is an agenda-setter. It sets the stage for debates to come. The all-too-brief discussion of topics with massive primary and secondary literatures should be seen as promissory notes. Isuspect that Clark, and other philosophers and empirical researchers, will be busy making good on thesepromissory notes for the foreseeable future.The upshot of all of this is, to my mind, that this is a truly important book. It is evocatively written and reflects atruly gargantuan amount of work. It sets the stage for future debates not only about the empirical merits ofBayesian characterizations of human cognition, but also the broader philosophical picture in which suchBayesian characterizations are embedded. I predict that many of us will be reading, discussing, and analysingthis book in the months and years to come.Andrew BuskellDepartment of History and Philosophy of ScienceUniversity of Cambridgeab2086@cam.ac.ukAcknowledgementsI am exceptionally grateful to both Andy Clark and Dan Williams for their helpful comments on earlier drafts ofthis review.ReferencesClark, A. [1989]: Microcognition: Philosophy, Cognitive Science, and Parallel Distributed Processing, Cambridge,MA: MIT PressClark, A. [1996]: Being There: Putting Brain, Body, and World Together Again , Cambridge, MA: MIT Press.Holton, G. [1975]: ‘On the Role of Themata in Scientific Thought’, Science, 188, pp. 328–34.4/4

Book review: Andy Clark // surfing uncertainty: prediction, action, and the embodied brain

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