Understanding ‘sensorimotor understanding’

Tom Roberts

Published online: 11 March 2009# Springer Science + Business Media B.V. 2009

Abstract Sensorimotor theories understand perception to be a process of active,exploratory engagement with the environment, mediated by the possession andexercise of a certain body of knowledge concerning sensorimotor dependencies. Thispaper aims to characterise that exercise, and to show that it places constraints uponthe content of sensorimotor knowledge itself. Sensorimotor mastery is exercisedwhen it is put to use in the service of intentional action-planning and selection, andthis rules out certain standard readings of sensorimotor contingency knowledge.Rather than holding between movements and sensory inputs or appearances,sensorimotor contingencies concern the suite of ways in which an object can berevealed through exploration. Sensorimotor knowledge is thus directed throughexperience to the world itself.

Keywords Sensorimotor understanding . Perception . Enactivism

Sensorimotor understanding

Perceptual content, according to sensorimotor theories, is brought forth through aprocess of active, exploratory engagement with the world. Experiences are theoutcome of more than a simple reception of sensory information: they depend upon asensitive and dynamic relationship between perceiver and object, an ongoing give-and-take that enables the coupling of one with the other over time (Noë 2002, 2004,2009a, b; O'Regan and Noë 2001; Hurley & Noë 2005; Myin & O’Regan 2009).Tactile perception, and the bodily contact it involves, is thus to be understood as theparadigm sensory modality, in contrast to the vision-centric tradition in philosophyand cognitive science. The perceiver must employ a battery of embodied skillswhichever modality she puts into operation.

Phenom Cogn Sci (2010) 9:101–111DOI 10.1007/s11097-009-9125-7

T. Roberts (*)University of Edinburgh, Philosophy Subject Area, Dugald Stewart Building,Edinburgh EH8 9 AD, UKe-mail: tom.roberts@ed.ac.uk

Exploratory manoeuvres through and around an environment engender systematicprofiles of sensory change that are contingent upon both the movements involvedand the manner in which features of the environment are located and arranged.Standard versions of enactivism require perceivers to possess and exercise a masteryor understanding of these suites of sensorimotor dependence. In order to undergoworld-directed perceptual episodes, the agent must in some way grasp the sensoryconsequences of her actions.

How this understanding ought to be specified, what it is for it to be exercised on agiven occasion, and the role it plays within enactivism are matters of somecontroversy1. My concern is to show that there are particular constraints set on whatcounts as the exercise of sensorimotor understanding, and that these in turn affecthow sensorimotor contingencies themselves are to be interpreted. A number ofalternative analyses of the structure of sensorimotor dependencies exist in theliterature, and the success of this approach relies upon their accurate characterisation.I argue that the exercise of sensorimotor knowledge should be understood in termsof its being put into the service of goal-directed activity, and that this entails thatsensorimotor contingencies do not concern the consequences of movement forsensory input or appearance, but the ways in which objects and their features can berevealed through exploration. This, in turn, limits the potential contribution toperceptual content made by sensorimotor factors.

The need for active perceivers to exhibit an understanding of sensorimotorcontingencies has been motivated by appeal to two central kinds of case: those inwhich the content of an experience is underspecified by sensory input, and those inwhich there is a perceptual deficit.

In the first instance, the exercise of sensorimotor understanding is said to providea sense of the perceptual presence of spatially-located physical objects withboundaries that extend beyond what is currently in view (Noë 2004, 2009a). InNoë's favoured example, a visual experience of the facing side of a tomato is givensubstance, as it were, by the perceiver's knowledge of the visually-relevantsensorimotor dependencies that apply to spheroid objects. The full content of theexperience is said to be underdetermined by current stimulation, while sensorimotorunderstanding provides the requisite extra. The perceiver receives information onlyabout the facing, unoccluded features accessible from her current perspective, andthe exercise of sensorimotor understanding is responsible for a sense of theirperspective-independent properties. Options exist concerning how best to specifywhat it is to be in sensory contact with the facing side of the object in cases likethese, and these will be considered below.

Examples of the second type involve individuals who undergo patterns of sensoryinput with a predictable and specifiable structure but who nonetheless fail to haveexperiences with the full content that characterises those of the modality in question.The post-operative cataract patient (Noë 2004) has an experience of patches ofcolour but (the story goes) cannot yet make sense of the ways in which they alter inresponse to his movements, and so the perceptual scene is not yet fully resolved into

1 Compare O'Regan and Noë's (2001) treatment to Noë (2004). Daniel Hutto (2005), furthermore, arguesthat sensorimotor understanding is superfluous, and that what determines the content of perception is theinstantiation of sensorimotor contingencies themselves

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individual objects and features but remains a sensory confusion. Similarly, a noviceuser of the tactile visual sensory substitution apparatus (Mandik 2005; Noë 2004)lacks the expertise to modulate sensory input through controlling the system with herbody, and so her experience lacks the genuinely perceptual nature of that of theproficient user. By hypothesis, the sensory stimulation undergone by the perceiverand non-perceiver respectively is relevantly similar in each case, and so thedifference is diagnosed as a deficit in the understanding of sensorimotorcontingencies, rather than as the failure of some sensory mechanism.

These examples are intended to indicate that there must be some perceptualknowledge on the part of the experiencer that is brought to bear during a perceptualepisode, and that it isn't sufficient for there merely to be a pattern of regularly-changing sensory stimulation. The perceiver must, in some sense, appreciate thesignificance of the input that she receives. The contribution of the exercise ofsensorimotor understanding, furthermore, is a constitutive one: the content added toexperience is constituted by the relevant body of knowledge being brought to bear,not caused or generated by it.

It is easy to see that sensorimotor understanding is more than simply a skilful,bodily mastery of certain action routines, even those that are appropriately sensitiveto the shape of the perceiver's environment. For sensorimotor knowledge must becapable of being exercised even where no large-scale bodily exploration occurs atall, and hence where input stimulation is for the most part static. This is obviousfrom visual cases, for example, in which one keeps one's eyes and head steady whileenjoying an experience without difficulty, or where the perceiver is paralysed orotherwise incapacitated2. Here, the bringing to bear of sensorimotor knowledgecannot be an exercise of embodied skills, for none are exhibited. Similarly, it will notsuffice for the agent to simply have the capacity to act out certain bodily routines, forshe is in possession of all sorts of unexercised abilities at a time, and it isn't clear thatthese can contribute to what she perceives.

The sensorimotor theorist must acknowledge, furthermore, that there are few ifany cases of perception3 whose content can be fully understood in terms of anagent's carrying out some skilful bodily exploration, for it will be rare for theperceiver to inspect every single facet of an item. Tomatoes can be seen as beingsolid, three-dimensional approximate-spheres without being exhaustively examinedfrom all angles. It is precisely this additional, perceptually-present or virtual contentthat sensorimotor understanding putatively contributes, and the concern about theunderdetermination of content by sensory input is most pressing in those instanceswith the least physical activity.

Not only is it the case that too few movements are actually performed (and hencetoo few sensory changes generated) to account for the richness of perceptualcontents, it is also true that bodily activity is too coarsely-grained to be a candidatefor the exercise of sensorimotor skill. The shapes of objects, for instance, are notvisually encountered by way of signature actions. There is no particular suite of

2 See Schellenberg's (2007) "sentient-statue" objection for more on these possibilities3 The exception being, perhaps, hypothetical cases in which an object is entirely enveloped by part of acreature's body

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head, neck and eye movements that characterises the perception of a cube, say4, anynumber of possible actions will do.

These considerations suggest that possessing sensorimotor knowledge does notamount merely to having or exercising the ability to move around (as a naive readingof the emphasis on skillful activity might have it); instead, it must be a kind ofunderstanding that concerns movement-induced changes, both actual and possible. Itis what regulates and makes sense of the perceptual information received by anactive perceiver, and allows her to predict that which would arrive were she toengage in particular activities, enabling her to experience objects as spatiallyextended and located, and as having properties with which she can make contact.

By restricting the role of the body in the exercise of sensorimotor understanding,we run contrary to the anti-representationalist spirit of enactivism. It is likely thatrejecting a skill-based or knowing—how understanding of sensorimotor activity willrelocate the bulk of the explanatory work back inside the head, with features ofembodiment relegated to a developmental rather than constitutive function inperception. What we need—and what I propose in what follows—is an interpretationof sensorimotor understanding and its exercise that is sufficiently cognitive to reflectits non-bodily emphasis, but sufficiently non-intellectual to accommodate infant,animal and unreflective perception.

The exercise of perceptual knowledge

If we construe sensorimotor understanding as concerning the possible and actualsensory consequences of movements, then we must attend to the difference betweena perceiver's possessing and exercising this knowledge. Only the latter is capable ofproviding the perceptual contribution to which the enactivist subscribes, for the merepassive storage of sensorimotor knowledge cannot plausibly determine the contentsof a given experience. It is a defining feature of enactivism that a particular, relevantbody of knowledge must be brought to bear during a perceptual encounter—abringing to bear which, recall, must be achievable without bodily movement. Anyaccount whose vocabulary sets this knowledge in terms of sensorimotor expectationor prediction is obliged to articulate what it is for these to be actuated.

A promisingway to interpret the bringing to bear of sensorimotor knowledge (variantsof which are present in O'Regan and Noë 2001; Clark and Kiverstein 2009; Hurley1998; although this emphasis is not present in Noë's more recent work) is to tie it to theongoing intentional behaviour of the perceiver, and understand it as being exercised(only) when it is put to use, somehow, in the selection and planning of action.

"For a creature (or a machine for that matter) to possess visual awareness, whatis required is that, in addition to exercising the mastery of the relevantsensorimotor contingencies, it must make use of this exercise for the purposesof thought and planning." (O'Regan and Noë 2001, section 2.6).

4 Although there may be a suite of movements of the hands and fingers that is characteristic of the tactileperception of a cube; an activity that enables the agent to keep her fingertips in contact with the surface ofthe object, for example. This feature seems to be peculiar to the tactile modality, though, and renders it anunhelpful model for the others

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Actions must not only be sensitive to sensorimotor details (for this can happenwithout perceptual awareness in cases where behaviour is not attended to by theagent), they must be chosen or selected at least partly on the basis of thesensorimotor profiles of relevant objects. It is possible, on this model, to see what itwould be for a creature to possess sensorimotor knowledge but to fail to deploy it—where it is not acknowledged as relevant to her decision-making—and to understandwhat it would take for sensorimotor contingencies to bear significance for the agent,a significance that shows up in how, where, and when she acts. By focusing onaction-oriented capabilities, this interpretation yields a kind of knowledge-exercisethat is available to individuals with limited conceptual and cognitive sophistication.It is not that sensorimotor understanding need be reflective or intellectual in nature,nor verbally reportable, nor fully conceptualised, but simply that its content be madeavailable to inform possible activities and interactions. Sensorimotor knowledgeneed not involve contents that are open-endedly recombinable with others; instead itmay be domain and task-specific, featuring only in a circumscribed range ofactivities with which the perceiver is familiar (Hurley 1998).

On the other hand, the selection of appropriate action-types and targets (Clark2001, 2007; Goodale 1998, 2001) involves sufficient offline intelligence to deflectthe charges of behaviourism to which sensorimotor stories are potentially vulnerable.Again, it is not that perception is to be reduced to a form of acting—as abehaviourist slant would have it—but that it is to be understood as involvingknowledge that enables successful, deliberate interaction, as and when it isappropriate. This emphasis fits well, too, with empirical evidence (e.g. Milner andGoodale 1995; Westwood and Goodale 2003) indicating that the role of perceptualprocessing is to deliver contents that are apt to inform action-planning, and higher-level classification and categorisation, while the details of finely-tuned action-guidance are left to non-perceptual processing streams.

While this reading of what it takes for sensorimotor understanding to be exercisedis not overly demanding—it does not require perceivers to be fully rational,reasoning agents—it does place constraints on candidate analyses of sensorimotorunderstanding itself: the content of sensorimotor knowledge must, at bottom, be thekind of thing that can figure in practical reasoning and deliberate action selection.This is not compatible with the details of certain existing sensorimotor approaches.

It is a source of difficulty, first of all, for the treatment offered by O'Regan andNoë (2001), who take sensorimotor dependencies to hold between movements andpatterns of subpersonal sensory stimulation (for example, constancies embodied inchanging activity in the mechanisms immediately downstream of the retina). Actionselection is a personal level affair, and hence not obviously sensitive to facts aboutbrain-level activity: choices concerning when, where, and how to act do not dependupon how each option will affect sensory input at the eye, for instance. While thebrain is no doubt 'tuned to' dependencies of movement and input in the ways thatO'Regan and Noë suggest, it isn't clear that the perceiver herself is able to exercisean understanding of these, especially if we are right to draw the connection betweenunderstanding and intentional behaviour.

The next option asserts that sensorimotor knowledge tracks changes to non-representational properties of an experience. This alternative—which is explicitlyrejected by Noë (2002, p60)—maintains that there are sensational properties (such as

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size and shape in a two-dimensional visual-field) of experiences, and that these alteras one moves around the environment. The region of the visual-field that is filled bythe profile of a distant object, for example, expands as one approaches it and detractsupon retreat. Even if this description of the structure of experiences is correct,however, knowledge concerning such non-representational features is, again, not thesort of thing that contributes to the selection of intentional actions. It is a species ofknowledge which, if it exists at all, is about states of oneself and not about the targetsor objects of one's world-engaging activity. Whichever way the perceptually-informed selection of actions is to be construed, we should expect it to be sensitiveto the properties (shape, size, location and spatial arrangement and so on) ofavailable entities, rather than of sensational properties of one's experience of thoseentities. This reading of sensorimotor understanding, then, is incompatible with theaction-selection interpretation of its exercise, and is not sufficient to secureperceptual content.

A third way to understand sensorimotor dependencies is to take them to holdbetween movements and the contents of perceptual experiences construed at thepersonal level5. On this view the content of an experience has a two-tier structure,with an initial level that depicts the scene from the perceiver's current perspectiveand a further level that fills out the experience by specifying perspective-independentproperties. For example, the first level of visual content may present the facing sideof the tomato, while the second (brought about by exercising one's mastery of howmovements affect one's experience of the facing side) depicts the whole tomato as anextended, space-filling entity. Here, the contribution to perceptual content made bythe exercise of sensorimotor understanding pertains only to a subset of the fullcontent available to the perceiver, that which corresponds to the completion ororganisation of the perceptual scene. It is what enables the post-operative cataractpatient to experience the world as being populated by objects and features once shehas gained an understanding of how contents specifying patches of colour vary asshe moves; and what expands the TVSS-user's experience beyond the limitedcontents delivered to her by the equipment at an instant.

Of course, this way of setting up the sensorimotor account brings with it theobligation to explain what is specified in the 'first level' of content and, crucially,how this is determined. Andy Clark has suggested that this kind of proposal "courtscircularity" (Clark, 2006, p3) by aiming to explain those contents that are broughtabout by sensorimotor activity in terms of further perceptual contents. I propose,

5 Noë (2002, 2004, 2009a) can be read as adopting this view, as when the content of experience isdescribed as 'two dimensional' (2009a, p2), and through the use of examples, like that of the post-operativecataract patient, that appear to fit this model naturally. However, Noë's account of the two-dimensionalityof experience is given an importantly nuanced treatment in his response to Campbell, Martin, and Kelly(Noë 2008), where both 'levels' of content are understood as direct encounters with parts of theenvironment, and neither is given precedence over the other.

The two-tier construal should be distanced, too, from subpersonal, computational treatments of vision(e.g. Marr 1982), on which multiple levels of content are iterated into an overall perceptual representation.Intermediate levels of content, on views of that sort, do not come about through the exercise of theperceiver's sensorimotor skills, but through subpersonal processing

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instead, that this structure simply limits the work performed by sensorimotorconsiderations to second-tier contents, and leaves the question of how the first tier'scontents are determined open, and consistent with a number of theories of perception(for instance, a direct-realist or a representationalist approach).

This brand of enactivism permits that there can be perceptual content that isnot contributed by the exercise of sensorimotor understanding, and that it ismovement-induced changes to this content that count as sensorimotor contingen-cies. Knowledge of these is appropriately world-directed, in contrast to the otherpossible options we have considered so far, as it concerns what is described inexperience, not how it is described. Once we correctly specify what it is that getsdepicted in the first level of content, we can see that sensorimotor knowledge isamenable to integration into the ongoing action-planning and selection of theperceiver.

Noë (2004, 2009a) claims that we experience suites of appearances,understood as objective properties of the external environment. Physical objectsare said to present a characteristic profile of appearance properties to surroundingpoints in space; properties that are determined by the size, shape, and spatialorientation of the object and its neighbours, and the relation that each point bearsto these. A plate viewed from its side presents an elliptical apparent shape, whilethe same object viewed from above presents a circular apparent shape; distantobjects present smaller apparent sizes than more proximate ones, and so on. Whena suitably receptive individual moves, she navigates a particular path from whichshe can perceive an evolving pattern of apparent properties. Sensorimotorknowledge is exhibited when she understands which appearances will (or would)be revealed by her activity, and this exercise is constitutive of her having aperceptual sense of the invariant, non-perspective-dependent properties thatunderpin those appearances.

Sensorimotor knowledge thus fills out the experience, taking it beyond the limitedsurface properties and appearances with which the agent is more superficially incontact, and it serves to resolve perceptual ambiguity: even though both an ellipticaland a circular object may present the same apparent shape, the perceiver can bring tobear her understanding of how each bears a signature sensorimotor profile in order tosee the perspective-independent shape of each.

Is this way of characterising sensorimotor knowledge compatible with its beingexercised through integration with action-planning and selection? I suggest not.Viewers rarely notice that they perceive apparent properties in addition toinvariances, and nor do they treat objects as though they possessed the apparentshapes and sizes to which Noë makes reference. It is therefore implausible thatknowledge of these properties—and knowledge that they will change in particularways in response to movements—is typically apt to figure in the planning andselection of the perceiver's behaviour. It simply doesn't matter to the agent's ongoingengagement with the plate that it will present an elliptical apparent-shape whenviewed from a tangent. Clark & Toribio (2001) point out that the sensorimotorproject is chauvinistic in placing too much weight upon finely-grained details ofsensorimotor contingencies that are immaterial to the agent. My point here isdifferent: that sensorimotor contingencies construed in this way make littledifference to the agent because they specify properties that have no bearing upon

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the selection of action in ordinary circumstances. Indeed, selecting one's actions onthe basis of the thinly-elliptical profile of the plate, rather than its actual circularshape, will result in treating it in inappropriate and unsuccessful ways6.

It can be sensibly denied (as Sean Kelly (2007), for example, does) that the first-level contents to which Noë makes reference standardly show up in experience. Analternative for the sensorimotor theorist involves eradicating appearance propertiesof this sort from first-tier perceptual contents, and considering them to depict simplythose parts of the constituents of a scene that are accessible to the perceiver from hercurrent location. Prior to the exercise of sensorimotor understanding, that is, what theperceiver visually encounters are the facing sides of unoccluded objects, someaspects of which may be hidden from view. While there may be a mathematically-specifiable array of 'apparent' shape and size profiles projected to each perspectivethat surrounds a scene, it is not these (nor how they alter as a consequence of theperceiver's motion) that are specified by the contents of experience. The plate doesnot look elliptical and round, on this story, it looks round and spatially located andoriented in a particular way.

On this view of first-tier contents, the role of sensorimotor understanding is, asbefore, to provide a sense of the perceptual presence of extended, space-fillingentities whose faces and edges continue out of view, and beyond the boundariesplaced by occluding obstacles. Sensorimotor contingencies thus hold betweenmovements and what is perceptually available; not between movements and'apparent properties' or between movements and patterns of subpersonal stimulation.Knowledge of sensorimotor contingencies involves knowing that one's activity willreveal hitherto-unseen parts of objects in regular and predictable ways, and althoughsuch revelation will be perceptually mediated, this doesn't mean that one'ssensorimotor knowledge is about one's own experiences—it looks throughexperience to the world itself.

Noë's most recent, explicitly naive-realist version of the enactive view (Noë 2008,2009b) adopts an interpretation that is similar to this, where sensorimotorunderstanding is said to be a precondition on making unmediated perceptual contactwith the world. The exercise of exploratory skills makes objects more fully availableto the agent in the same way that linguistic understanding makes available thesemantic content of an utterance, for example. Perceptual contact with an object'sinvariant, perspective-independent properties involves an 'encounter' with its merelyapparent features, an encounter that, according to Noë, does not need an explanationthat is autonomous of the general account (Noë, 2008, p701). Whilst this apparentcircularity is described as a "healthy" one (Noë, 2008, p700), it remains unclear howthe exercise of sensorimotor knowledge is to be understood here, as any emphasis ofthe role of knowledge concerning sensory changes appears to be in tension with the

6 In certain cases, knowledge of appearances does seem to figure in intentional behaviour, as when asniper gauges the aim of his rifle according to the apparent size and shape of a distant target viewedthrough a telescope, or when an artist judges the proportions of his painting according to apparent sizes inthe visual field (thanks to an anonymous reviewer for pressing this point, and for these examples). These, Isuggest, involve expertise concerning a specialised domain, and do not show that such knowledge forms apart of everyday experience

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denial of the primacy of the sensory encounter with appearances, and with the claimthat nothing is given in perception (Noë, 2008, p697)7.

On my view, the properties grasped by the perceiver are a species of affordance,where what is afforded by a particular object includes a certain exploratory profile—a suite of ways in which the object can be revealed to the perceiver. Furthermore, theagent understands this revelation: she knows that the back of the object, for instance,is present and available for contact and interaction. The perceptual presence of thewhole object is achieved through knowing that it is there to be explored and engagedwith, not that it is the locus of a particular profile of experiences. Now, finally, wehave a brand of knowledge that is potentially apt to make contact with the practicalreasoning and action-selecting capacities of the perceiver; a kind of sensorimotorunderstanding whose exercise we can make sense of in terms of its featuring indecision making. The skilled perceiver, when faced with a familiar object, has agrasp of how to engage with that item in order to explore and make use of itspossibilities; she knows both how to move and what her movements will reveal. Herexpectations do not concern possible experiences—and so she need not be able tothink about her own perceptual states—but rather the parts of objects that arecurrently inaccessible, and how to access them.

The enactive perceiver has a practical understanding of the objects around her:not only an embodied mastery of how to navigate and explore them, but of howthese movements and the possibilities they afford fit in with her goals and plans.Perceptual exercise of this understanding involves a recognition of when and wherea particular suite of affordances is present. Perceiving the solid, 3-dimensionalcharacter of the tomato is a matter of recognising that the whole object is there to beacted upon, that its extended shape has a significance for action. This does not implythat the perceiver's awareness of the far side of the tomato involves being able todraw rational inferences about it, or to think about it in general terms; its significancemay be limited to a circumscribed range of familiar activities. The skilled perceiveris akin to the individual who not only possesses the abilities necessary to ride abicycle, but who can recognise the kinds of object that afford bicycle-riding, and sois capable of performing the right actions at a time that is appropriate both to what isavailable before her, and to her own wants and needs. In bringing to bearsensorimotor mastery, the perceiver understands that the items in front of her areimmediately available for the purposes of bodily interaction, where this is interactionis constrained by the items' physical makeup.

This reading is beneficial for it provides consistency between sensorimotorknowledge and other forms of perceptual understanding that are capable of influencingthe contents of an experience, and that concern objects and events. Sensorimotorknowledge is on a continuum with, for example, the linguistic comprehension thatenables an individual to perceive the meanings of written and spoken words, and theunderstanding of event-types that helps to determine the perception of temporal andmusical properties in auditory experience (Noë 2006, 2008). To this scale we might addthe agent's practical understanding of objects' physical properties and how they can bedealt with—their solidity and weight, resistance to pressure and change and so on—

7 If the healthy circle here can be sustained, then I offer my characterisation of the exercise ofsensorimotor understanding as compatible with, rather than a competitor to, Noë's direct realist model

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and, where present, more sophisticated knowledge of categorisation and classification.These are forms of understanding that enable the perceiver to make sense of what ishappening out in the world, rather than within her own perceptual or informationalstates, and we ought to view sensorimotor mastery in these terms as well.

Conclusion

By considering what it could be for an agent to exercise sensorimotor knowledge, weuncover certain constraints on the possible contents of such knowledge, and henceon the possible structure of an activist account of perception. The key features ofsensorimotor understanding—if it is to contribute to the content of experience—arethat it be a personal-level phenomenon capable of being brought to bear even whenthe bodily skills of the individual in question are not acted out. It is not a form ofknow—how, nor simply of expectation, for neither of these fully capture theoccurrent, active nature of its exercise by the perceiver. A grasp of sensorimotorcontingencies is only deployed when it is poised to figure in the agent's planning andaction-selection, where this does not require full-blown rationality.

It is not clear that knowledge of sensorimotor contingencies as interpreted bycertain influential models of enactive perception can be exercised in this way, forthere is a mis-match between what is depicted by this knowledge and the demands ofcapacities devoted to action-selection and deliberation. An understanding ofdependencies that hold between movements and patterns of sensory stimulation,firstly, is not apt to feature in an agent's reasoned, world-engaging behaviour. Nor isit the case that knowledge concerning so-called 'apparent properties'-best construedas the profiles that a perceptually-encountered object would project onto a two-dimensional screen perpendicular to the line of sight—is appropriate to the selectionof actions that must be sensitive to the perspective-independent features of objects.

Taking sensorimotor contingencies to hold between movements and the revelationof currently-occluded parts of objects offers a successful alternative, becauseknowledge of these specifies properties that are relevant to the selection of actions;namely, the properties of physical entities. In possessing sensorimotor knowledge,the perceiver understands how to explore her environment, and what will be revealedto her as she does so. Exercising this understanding is a matter of recognising thatcertain possibilities can be employed in the service of goal-directed activity,empowering the agent to fully engage with the opportunities presented by the currentenvironment. Perception is not itself a bodily activity, but it does underpin suchactivity—it makes possible fluid, interested interaction with the world.

References

Clark, A. (2001). Visual experience and motor action: are the bonds too tight? Philosophical Review, 110(4), 495–519.

Clark, A. (2006). Vision as dance? Psyche, 12(1), 1–10.Clark, A. (2007). What reaching teaches: consciousness, control, and the inner zombie. British Journal of

the Philosophy of Science, 58(3), 563–594.

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Clark, A, & Kiverstein, J. (2009). Slipping the mesh. Behavioral and Brain Sciences.Clark, A., & Toribio, J. (2001). Sensorimotor chauvinism? Behavioral and Brain Sciences, 24(5), 979–

980.Goodale, M. (1998). Where does vision end and action begin? Current Biology, 8(14), R489–91.Goodale, M. (2001). Real action in a virtual world: commentary on O'Regan & Noë. Behavioural and

Brain Sciences, 24(5), 984–985.Hutto, D. (2005). Knowing what? Radical versus conservative enactivism. Phenomenology and the

Cognitive Sciences, 4(4), 389–405.Hurley, S. (1998). Consciousness in Action. Harvard University Press.Hurley, S. & Noë, A. (2005). Can Hunter-Gatherers Hear Colour? In Brennan, G., Goodin, R. and Smith,

M. (Eds) Common Minds: Essays in Honour of Philip Pettit. OUP.Kelly, S. (2007). Content and constancy. Philosophy and Phenomenological Research, 76(3), 682–690.Mandik, P. (2005). Action-oriented representation. In Kathleen Akins & Adrew Brook (Eds.), Cognition

and the Brain: The Philosophy and Neuroscience Movement. Cambridge: Cambridge UniversityPress.

Marr, D. (1982). Vision. New York: W.H. Freeman.Milner, D., & Goodale, M. (1995). The Visual Brain in Action. OUP.Myin, E., & O’Regan, J. K. (2009). Situated perception and sensation in vision and other modalities: a

sensorimotor approach. In P. Robbins & M. Aydede (Eds.), Cambridge Handbook of SituatedCognition. Cambridge, UK: Cambridge University Press.

Noë, A. (2002). On what we see. Pacific Philosophical Quarterly, 83(1), 57–80.Noë, A. (2004). Action in Perception. Cambridge, MA: MIT.Noë, A. (2006). Experience of the world in time. Analysis, 66(289), 26–32.Noë, A. (2008). Reply to Campbell, Martin, and Kelly. Philosophy and Phenomenological Research,

LXXVI(3), 666–673.Noë, A. (2009a) Real presence. Philosophical Topics.Noë, A. (2009b) Conscious reference. Philosophical Quarterly.O'Regan, J. K., & Noë, A. (2001). A sensorimotor approach to vision and visual consciousness.

Behavioural and Brain Sciences, 24(5), 939–973.Schellenberg, S. (2007). Action and self-location in perception. Mind, 116(463), 603–632.Westwood, D. A., & Goodale, M. A. (2003). Perceptual illusion and the real-time control of action. Spatial

Vision, 16, 243–254.

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