Visual Spatial Awareness Probably Requires Visual Awareness of Space

Bartek Chomanski (University of Miami)

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1. Seeing “What” without Seeing “Where”

Consider the scene before your eyes. There’s probably a computer screen you see right in front of you; a coffee cup to your right, within easy reach; a wall behind the computer screen; a stack of papers to grade on your left. In a typical visual experience, you see objects at particular, egocentrically specified locations in external space. But, for broadly Kantian reasons, this (seeing objects at locations in space) doesn’t seem like a merely contingent feature of our experience. It appears unimaginable, perhaps even inconceivable, that we could ever visually experience objects without experiencing them as occupying space at all. Yet, this position has recently come under sustained attack by John Schwenkler (2012). Schwenkler enlists the results of some experiments carried out on a patient with Balint’s syndrome[1] (Friedman-Hill, Robertson, & Treisman, 1995) to show that they constitute a counterexample to the claim that the experience of space is necessary for visual spatial awareness of objects.

One of the best-studied patients with Balint’s syndrome is known in the literature as RM. RM’s performance in various experiments seems to suggest that his ability to perceive spatial objects does not require the ability to perceive “absolute space” (Schwenkler, 2012). In particular, RM seems unable to locate the objects he’s perceiving anywhere in space, and yet, he’s able to accurately identify the objects’ shapes. This has led Schwenkler to postulate that RM doesn’t perceive the objects as in space at all.

In this paper I argue that Schwenkler’s conclusion is premature. I sketch an alternative explanation of the data which preserves the necessity claim and which can account for a variety of RM’s results reported in other experiments, beside the one that Schwenkler appeals to. Craig French (2015, forthcoming) has also recently offered alternative explanations of RM’s results that don’t necessitate Schwenkler’s conclusion. My interpretation appears to differ from French’s (2015), and can be read as a further development of his (forthcoming). In Section 2, I present Schwenkler’s argument; in Section 3 I interpret RM’s results in terms of indeterminate spatial content of experience and show that this interpretation doesn’t require Shcwenkler’s radical conclusion. In Section 4 I review other experimental results on RM and suggest that they appear to support my interpretation over Schwenkler’s.

2. Does RM fail to Perceive Space?

The argument proposed by Schwenkler seems to be premised on the idea that RM fails to perceive objects’ locations and orientations, but he does perceive the objects themselves. Schwenkler writes:

RM had suffered a pair of strokes that resulted in severe damage to his posterior parietal cortex, and as a consequence was unable to localize the objects he saw. For example, when shown a display with a target at one of five locations along the vertical or horizontal meridians and told to report whether the target’s position was up, down, or center (in the vertical blocks) or right, left, or center (in the horizontal ones), RM averaged only 70% correct across all conditions. Similarly, when instructed to judge the relative position – left or right in one block, up or down in the other – of an „X‟ with respect to that of an „O‟ that was also presented on the screen, RM was correct approximately 50% of the time, a performance no better than chance (Friedman-Hill et al., 1995). RM could detect the target stimuli well enough; he just couldn’t tell where they were, either on the screen itself or with respect to other things.

Moreover, RM explicitly denies awareness of the objects’ locations. He is also unaware of their orientations. Schwenkler concludes that RM did not, at the time of the experiment, perceive the objects as arranged in a larger spatial framework: “his experience was of a wholly unimaginable sort: not of oriented spaces that were cut off at the boundaries of the things that occupied them, but of things without spatial locations or orientations. RM perceived shapes that did not appear to be in space at all.” If Schwenkler is correct, then RM’s experience falsifies the thesis that experience of spatial objects requires a representation of space as some sort of overarching framework.

However, the conclusion that Schwenkler draws does not actually follow. The inability to perceive where the objects are, or how they are oriented does not entail the lack of awareness of these objects as being within an overarching spatial framework. RM’s results are consistent with the view that he does perceive objects as in space, but the kind of information about their location he is able to consciously access is severely limited. In the next section I outline the interpretative framework that I think captures RM’s results reported by Schwenkler but does not entail his radical conclusion. After that, I offer some tentative reasons why this interpretation should be preferred.

3. Determinacy and Spatial Vision

My interpretation of RM’s predicament is simple. On my view, rather than failing to experience the object as in space at all, RM’s experience of the objects’ spatial locations within the larger space is indeterminate with respect to most spatial relations.

Indeterminacy in the content of visual experience is not at all an alien idea. It is appealed to when explaining how our peripheral vision represents the environment (e.g. Nanay (2015), Stazicker (2011)), and when explaining what the experience of Type-2 Blindsight patients is like (Brogaard (2015)). Furthermore, it appears that it is not odd to ascribe some indeterminacy to the spatial content of location experiences in ordinary conscious vision. Consider the case described by Susanna Siegel (2006):

Consider two experiences of seeing a rabbit, in both of which a rabbit looks to be in a certain direction and at least distance D away from the speaker [sic]. Let us suppose that there really is a rabbit (that looks the way the experience characterizes it) in that direction and at that distance away, but that, in one case, the rabbit is at L1, whereas in the other, it is just slightly to the left, at L2. Now, if the rabbit is far enough away, it seems plausible to suppose that these experiences could be phenomenally indistinguishable from one another. The question then arises whether either is falsidical with respect to location. If we hold constant everything else about the two situations besides the location of the rabbit seen, then it seems implausible to classify one as falsidical with respect to location and the other not. If both experiences are veridical, then the experience will be indeterminate with respect to whether the rabbit is at L1 or L2.

In general, Siegel’s point can be expressed thus: if two experiences of objects which are in fact at different locations are phenomenally indistinguishable with respect to the objects’ experienced location, then the experience is indeterminate with respect to location. Siegel shows that it’s plausible that small-scale indeterminacy is involved in ordinary vision. But we can put the indeterminacy described by Siegel to further use. Consider an auditory experience of the following sort: You have your eyes closed and you hear two people talking. The spatial content of your auditory experience doesn’t specify the spatial relation between the two voices’ locations. You can’t tell who’s to the right of whom. That is, you seem to perceive two objects without being able to perceive how they’re spatially related to one another, what their orientation is, etc. Your experience is wholly indeterminate as to how the two sources of sound are aligned on the left-right axis. That is, it is wholly indeterminate with respect to some spatial relation. If you were asked where the sources of the sounds you’re hearing are, with respect to one another, you’d be at a loss. But it wouldn’t thereby follow that you would experience the voices as not in space at all.

The same indeterminacy doesn’t arise for normal vision, however. Normally, when you see two objects, you experience where they are with respect to one another on the left-right axis.

So, it looks like some experiences are better are representing space (and at representing objects’ locations in particular) than others: the better (at representing space) an experience is, the more determinate spatial content it has. Vision is typically better than audition in that respect. It represents spatial properties and relations in a more determinate way than audition.

I propose that we take RM’s experience to involve just such indeterminacy extended to most (if not all) ways of visually experiencing spatial locations of objects. As the results that Schwenkler appeals to suggest, RM’s experiences of X’s and O’s are (sometimes) phenomenally indistinguishable, even though sometimes X is to the left of the O, and other times it’s to the right. Hence, it makes sense to say that RM sees those objects as occupying indeterminate spatial locations. Since the indeterminacy with respect to the experienced location doesn’t preclude seeing objects as in space, RM’s experience is not an experience of objects as not in space at all. Hence, Schwenkler’s conclusion is not mandatory.

To make more concrete the idea that complete indeterminacy in the awareness of location doesn’t preclude awareness of the object as in space, consider the following story: If all I know about the location of a bear is that it’s outside (that’s all I heard on the radio, say), and then you’d ask me where the bear is, I could reasonably say that I don’t know, especially if I assumed you meant a specific spatial location, or a specific relation to some other place, e.g. our favorite spot in the woods, or even with respect to my own point of view or your body or whatever. Further, if I kept switching radio stations only to find out from their reports that the bear is outside (perhaps each formulated in a different way, or sometimes in a different language), and you kept asking me for (what I’d assume would be) its precise location or orientation, I’d continue denying knowledge of that. It would not, however, mean that I’m not aware of the bear as in space at all. My representation of the bear’s spatial relations would be impoverished but not nonexistent. I would be aware of the bear as occupying an indeterminate location. The data Schwenkler cites (RM’s poor results when determining the locations of objects) is consistent with RM’s possessing such an impoverished capacity to represent space as such.

I take it that anyone in RM’s situation would be confused by not being able to perceive the precise location of objects one used to be able to localize precisely. This inability would presumably lead some rational persons to make reports that RM is quoted as making (“I can’t see where it is”); it would, it seems, make a rational person particularly reluctant to guess the location of the stimulus.

Sure, RM’s representation of space is severely impaired. But, arguably, it could be that it’s impaired in roughly the way my representation of the space surrounding the bear is. In particular, RM can experience the objects as occupying determinable locations, without perceiving determinate locations, just like I know that the bear is at some determinable location without knowing where it is. The difference is, of course, that I’m learning about the bear through testimony, and RM is learning about the object(s) through sensory experience. But that doesn’t seem to show that what (the kind of information) we learn has to be different.

In other words, an alternative interpretation of RM’s case is that he has a conscious representation of objects (perhaps serially rather than simultaneously) as occupying determinable, but not determined, locations in space, perhaps against some undifferentiated background. Hence, RM’s experience is not a counterexample to the thesis Schwenkler sets out to refute. It’s possible to represent an object as in space without representing its location in a determinate way. The inability to localize an object in space is not sufficient to show that the object is not experienced as occupying space.

Overall, the experimental results and the patient’s reports Schwenkler appeals to are consistent with the idea that RM’s visual experience might represent location broadly enough that little information useful to do well in the experimental paradigm could be extracted from this representation. Schwenkler seems to assume that to represent something visually as in space, we need to represent its precise location. But this isn’t a necessary truth. Spatial representation is varied. The confusing nature of RM’s reports might reflect the unusual poverty of his visual experience of space (especially visual experience of location), rather than the complete absence of the representation of space as such.

3.1 Lack of Orientation Awareness Does not Entail Lack of Awareness of Space

Above I discussed the first reason one might be reluctant to ascribe conscious representation of space to RM, namely his inability to localize objects. In this section, I discuss the second reason why RM is taken to lack visual awareness of space: his inability to get the orientation of seen objects right. RM is able to recognize objects (such as letters or short words); hence, he is able to represent fairly detailed intrinsic spatial relations (those holding between parts of the object) without being able to recognize the objects’ orientations. This leads Schwenkler to conclude that RM doesn’t perceive the objects as in space at all.

However, correctly identifying a complex object does not appear to require correctly identifying its orientation even in ordinary experience. Ordinary humans, as it turns out, are fairly good at categorizing pictures (telling what the picture is a picture of) even when the pictures are presented to far peripheral vision. E.g. subjects performed way above chance even for stimuli appearing at eccentricity 51.5° when the task was to categorize the target stimulus as belonging to a certain kind, e.g. animal (Thorpe, Gegenfurtner, Fabre‐Thorpe, & Buelthoff, 2001). There is thus a good reason to believe that we’re able to recognize the objects even in such unfavorable conditions.

Yet, results of a different experiment, ran on visually unimpaired subjects (Sally & Gurnsey, 2003) provide evidence that, when an object is presented to peripheral vision, we are not very good at determining its orientation. In Sally’s and Gurnsey’s experiment, the subjects’ judgments of the spatial orientation of the stimulus were poor (at chance) when the stimulus was removed from foveal vision even by as little as 8°. This suggests that the ability to correctly categorize a complex stimulus and the ability to correctly report stimulus orientation could come apart even in ordinary (peripheral) vision. But it doesn’t seem right to say that the stimuli that are correctly categorized are experienced as not in space at all. Hence, RM’s results in which he was able to correctly identify objects without being able to correctly determine their orientation don’t show that he perceived the complex objects as not in space.

Consequently, it looks like RM’s results do not require us to accept Schwenkler’s conclusion. RM is able to perceive space.

4. Other Experiments Suggest that RM is Able to Perceive Space

Additionally, Schwenkler’s interpretation of what RM’s experience is like is inconsistent with a range of other experimental results and observations made on RM. Firstly, Robertson et al. (1997) report that even though RM did poorly in identifying which of the array of objects was in motion, he nonetheless “frequently reported seeing motion in displays that included no moving objects … He would complain that the stationary letter whose color or identity he was naming was drifting about on the screen.” Now, it does seem impossible to experience the motion of an object[2] without experiencing a change of the object’s position relative to some reference frame. RM couldn’t have experienced the letters moving, had he not experienced them as changing locations. It is difficult to see how such an experience could be accounted for while maintaining that RM is unable to see the moving object as in space.

Another set of results that appears inconsistent with Schwenkler’s view is the data on reaching in RM (Baylis & Baylis, 2001). In the experiments, RM is asked to reach to one of the twelve locations at which a point of light appears. He is better than chance, though his results still are low for the task that’s relatively easy. The results of these experiments suggest that RM’s grasp of locations in egocentric space is fairly good. But being able to locate an object in egocentric space seems to imply some ability to experience the object in relation to oneself. And hence, as occupying the same spatial framework.

However, care should be taken when drawing conclusions about spatial perception from the tasks requiring the subject to perform an action. Given the empirical discoveries concerning the two visual systems hypothesis (Goodale & Milner, 1992), the reaching data should not be used as evidence for what kind of experience RM is a subject of. This is because, roughly speaking, the system guiding visual action and that responsible for conscious vision function largely independently of one another, and the results from experiments examining visually-guided action should not be used to form conclusions about visual experience (or, more generally, visual perception).

Interestingly, Baylis & Baylis have also examined RM’s ability to report on perceived stimuli without engaging in reaching behavior. In one experiment, RM was required to merely name (without reaching) the location at which the stimulus appeared (in egocentric terms) and, again, his errors, though multiple and more frequent than in the reaching task, are mostly mistakes concerning depth (RM gets the direction—left, right, center—correct much more often than chance, but he frequently seems incapable of judging correctly whether the objects are nearer or farther away from him). Mistakes in direction but not the depth of the stimulus were rarer, mistakes in both, rarer still. There then seems to be a good case for thinking that RM perceives the object at least in relation to himself, and even that, in part, the perception is accurate (after all, he was above chance, though not as good as regular perceivers, in determining whether the object appeared on the left or right). There is, then, at least an implicit representation of one object (himself) spatially related to another (images on the screen). And for this, it seems that representing these objects as occupying a single spatial framework is required.

Similarly, another set of experiments conducted on RM by Phan et al. (2000) suggests, in the experimenters’ own words, that RM “has some ability to localize stimuli with respect his own body” and that he is able to use an egocentric frame of reference to do so. This, in turn, suggests that RM can experience objects as in a place that’s distinct from the one his body occupies. Plus, the use of an egocentric frame of reference implies some ability to represent objects as occupying the same space as his body does.

All these results point to the idea that RM must have some representation of the spatial locations of the stimuli he sees, albeit each suggest some impoverished representation. But Schwenkler’s claim concerns different results in a different task. So how does the above relate to the experimental results that Schwenkler appeals to? Why should the experiments just reported have any bearing on Schwenkler’s interpretation?

It might be said that the experiments Schwenkler bases his interpretation on were made earlier than the ones conducted by Baylis & Baylis and Phan et al. RM’s condition may have improved by the time he was examined the next time. Or, it might be that the nature of the tasks was different enough that the experiences evoked were correspondingly different. These points are well-taken. It seems to me, however, that one reason that may be offered to offset the strength of these points is that we may explain all the experimental data (i.e. those appealed to by Schwenkler, and those related above) by postulating impaired, but not non-existent representation of space. In this way, RM’s improvement over time would be one of degree (increasingly more detailed representation of spatial location) rather than in kind (some representation of space vs. no representation of space). We would have to give divergent explanations of the two sets of results, if we work along the lines that Schwenkler recommends. A (more) unitary explanation seems better than a non-unitary explanation. A less radical explanation seems better than a more radical one.

One could also reply that the interpretation I’m offering makes RM’s experience impossible to imagine. But this makes it no worse off than Schwenkler’s who says, after all, that RM’s experience is not the kind we could picture to ourselves at all.[3]

5. Conclusion

Experimental results gathered from RM threaten to undermine the Kantian thesis that visual awareness of space is required for visual awareness of objects. I have offered a sketch of an alternative interpretation of these results. My interpretation seems able to explain the data taken to refute the thesis, plus it enables us to explain other results of experiments on RM in terms of gradual improvement of his perceptual capacities, rather than as a radical improvement in kind. The existence of an alternative interpretation shows that Schwenkler’s radical claim concerning the nature of spatial representation is not mandatory.

 

 

Bibliography

Baylis, G. C., & Baylis, L. L. (2001). Visually misguided reaching in Balint’s syndrome. Neuropsychologia, 39(8), 865-875.

Brogaard, B. (2015). Type 2 blindsight and the nature of visual experience. Consciousness and Cognition, 32, 92-103.

Foley, R. (2015). The case for characterising type-2 blindsight as a genuinely visual phenomenon. Consciousness and Cognition, 32, 56-67.

French, C. (2015). Bálint’s Syndrome and the Structure of Visual Experience.  Retrieved from http://craigafrench.github.io/assets/CFBalintsPaper.pdf

French, C. (forthcoming). Object seeing and spatial perception. In F. Dorsch, F. Macpherson & M. Nida-Rümelin (Eds.), Phenomenal Presence: Oxford University Press.

Friedman-Hill, S., Robertson, L. C., & Treisman, A. (1995). Parietal contributions to visual feature-binding: Evidence from a patient with bilateral lesions. Science, 269, 853-855.

Goodale, M. A., & Milner, A. D. (1992). Separate visual pathways for perception and action. Trends in Neurosciences, 15(1), 20-25.

Lee, G. (2014). Experiences and their parts. In D. Bennett & C. Hill (Eds.), Sensory integration and the unity of consciousness (pp. 287-322). Cambridge, Mas.: The MIT Press.

Nanay, B. (2015). Perceptual content and the content of mental imagery. Philosophical Studies, 172(7), 1723-1736.

Robertson, L. C. (2003). Binding, spatial attention and perceptual awareness. Nat Rev Neurosci, 4(2), 93-102.

Robertson, L. C., Treisman, A., Friedman-Hill, S., & Grabowecky, M. (1997). The interaction of spatial and object pathways: Evidence from Balint’s syndrome. Journal of Cognitive Neuroscience, 9(3), 295-317.

Sally, S. L., & Gurnsey, R. (2003). Orientation discrimination in foveal and extra-foveal vision: Effects of stimulus bandwidth and contrast. Vision Research, 43(12), 1375-1385.

Schwenkler, J. (2012). Does visual spatial awareness require the visual awareness of space. Mind & Language, 27(3), 308-329.

Siegel, S. (2006). Subject and object in the contents of visual experience. Philosophical Review, 115, 355-388.

Stazicker, J. (2011). Attention, Visual Consciousness and Indeterminacy. Mind & Language, 26(2), 156-184. doi: 10.1111/j.1468-0017.2011.01414.x

Thorpe, S. J., Gegenfurtner, K. R., Fabre‐Thorpe, M., & Buelthoff, H. H. (2001). Detection of animals in natural images using far peripheral vision. European Journal of Neuroscience, 14(5), 869-876.

Weiskrantz, L. (2002). Prime-sight and blindsight. Consciousness and Cognition, 11(4), 568-581.

 

Notes

[1] Lynn Robertson’s gives the following characterization of Balint’s syndrome: “Balint’s syndrome is a neuropsychological disorder that results from damage to both parietal lobes. Clinically, it includes three main symptoms: simultanagnosia (the inability to see more than one object at a time); optic ataxia (the fixation of gaze with severe problems in voluntarily moving fixation); and optic apraxia (the inability to reach towards the correct location of perceived objects)” (2003)

[2] It seems possible, however, to represent motion as such, without having to represent an object moving against some background. Blindsighted subjects provide one example (Foley, 2015; Weiskrantz, 2002). Noticing motion somewhere in your peripheral vision might count as another example (Lee, 2014).

[3] But, to engage in pure speculation, one might perhaps think that my interpretation offers us a way of grasping imaginatively RM’s predicament thus: perhaps his experience in his entire visual field is not unlike what we experience in the periphery. While this is pure speculation, it’s interesting to note that the responses of people tasked by Thorpe et al. with categorizing images shown to their peripheral vision indicate similar unwillingness to guess as do RM’s reports.

9 thoughts on “Visual Spatial Awareness Probably Requires Visual Awareness of Space”

  1. I’ll begin by providing some context for this commentary. Schwenkler 2012 argues that the experience of Bálint’s Syndrome patient RM presents an empirical challenge to what he calls the Apriority Thesis (AT):

    At least in the domain of visual experience, it is impossible for there to be spatial perception (i.e. perception of spatial objects, properties, and relations) without the awareness of space (i.e. ‘space in the strict sense’, or an overarching and somehow ‘absolute’ space within which everything is perceived as situated).

    Such visual awareness of space, Schwenkler writes, is an “awareness of the sort of thing that Newton (and Kant) supposed could be ‘empty’ and was somehow independent of the objects within it, and that according to the Apriority Theorist constitutes a kind of experiential framework within which all particular spatial things are necessarily represented as situated” (310).

    It is helpful to locate the AT in relation to the idea that normal visual experience is structured by a three-dimensionally organized visual field, a cone-shaped region of physical space within which distinct objects are experienced at distinct locations and as spatially related to one another (as well as to potentially empty regions of that space). This space, Michael Martin (1992, 1993) has suggested, is the “form” of normal visual experience. On Martin’s view, normal visual experience is an experience both of objects in space as well as an experience of the space in which they appear to be located, a space “there to be experienced whether or not any objects are present.” AT goes beyond this view in claiming that visual experience in general – and not just normal visual experience – is structured by a field in Martin’s sense. There is probably more built into AT than this claim, but I think that AT entails that all visual spatial perception, for example, visual perception of 3D shape, requires awareness of the contents of a more or less extensive visual field.

    French (forthcoming) considers whether Bálint’s Syndrome, in particular, simultanagnosia, constitutes a challenge to the Spatial Location Claim:

    Seeing an object requires seeing some of the object’s spatial location properties or, at least, seeing the object as being in a spatial location.

    French argues that while sources experimental evidence and first-person reports support the view that RM can’t experience an object’s determinate location properties, he can nonetheless experience its location in a maximally indeterminate way: “even individuals with Bálint’s Syndrome can see objects to be located. It is just that they don’t see objects to be located in particular locations. That is, it is consistent with the idea that in seeing an object an individual with Bálint’s Syndrome sees that object’s property of being somewhere or other, even if they can’t see precisely where” (draft, 33-34). On French’s view, all of the available evidence is consistent with the claim that RM can visually experience an object as having a maximally determinable spatial location, that is, as having the property of being located, of being somewhere (draft, 34). Let’s call this the Determinable Spatial Location Claim (DSL).

    This brings me to Chomanski’s contribution. According to Chomanski, if DSL is true, then Schwenkler is wrong to argue that RM’s experience is in violation of AT: “Since the indeterminacy with respect to the experienced location doesn’t preclude seeing objects as in space, RM’s experience is not an experience of objects as not in space at all. Hence, Schwenkler’s conclusion is not mandatory” (4). I would like to make two points in connection with this proposal.

    First, RM’s putative capacity to experience a single object at a time as somewhere – that is, as having a location, but no location in particular – does not appear to satisfy the condition at the heart of AT. Recall that AT entails that visual experience, in general, is structured by a field in Martin’s sense. So even if DSL were true, this wouldn’t by itself mean that RM’s experience is consistent with AT. Somewhere, for RM, is never somewhere in a visual field because RM doesn’t have a visual field – a point emphasized by French (in preparation). (Martin, I presume, would also accept this point. “It is doubtful,” he writes in his 1993 paper, “whether the idea that the experience of space is central to spatial experience holds for vision in general. It seems implausible to suppose that a subject who can identify the shapes of seen objects, but fails to locate them, experiences them all within a region of space which is itself experienced.”)

    Second, it is not entirely clear what DSL claims: there are different ways of explaining what it is for a visual experience’s spatial content to be indeterminate. Here are three possibilities. First, noise in the visual system, limits on spatial resolution/acuity, and limits on sources of depth information all affect how precisely the location of an object is estimated. As precision goes down, the range of determinate locations consistent with the correctness of the estimate goes up. So one way to unpack the idea of indeterminate spatial content is in terms of perceptual precision and intervalic/range content (Block 2015, Stazicker forthcoming). Alternatively, one might appeal to the idea of “perceptual confidence,” that is, the idea that visual experience represents something like a posterior probability distribution (Morrison 2016). When our perceptual confidence concerning the location of a visually experienced object is very low (for all possible visible locations), we could say that our experience of the object’s location is highly indeterminate. Finally, one might appeal to evidence that the visual system computes ensemble representations or summary statistics for objects that are unattended or in peripheral vision (for a recent review, see Cohen et al. 2016). In relevant cases, visual experience only represents the statistical tendency of an ensemble of objects with respect to a feature, for example, average lightness, orientation, or direction of movement. So we could also say that the spatial content of a visual experience is indeterminate when its content reflects an ensemble representation of some spatial feature belonging to a group of objects.

    I think that there are problems with saying that RM’s visual experience is indeterminate in any of these three senses. For starters, it clearly can’t be indeterminate in the third, ensemble-representation sense, since, as a simultanagnosiac, RM only experiences a single object at a time. And it is hard to see that it could be indeterminate in either of the first two senses. RM’s visual experience can’t represent an object’s location as falling somewhere within a maximally wide range of determinate locations if RM, by hypothesis, is not capable of representing the determinate (egocentrically or allocentrically specified) location of any object. Similarly, experiencing a probability distribution with respect to an object’s location in space presupposes, I take it, an intact capacity to represent the different possible locations at which the object might be situated. It doesn’t make sense to say that RM’s perceptual confidence concerning an object’s location is low for all possible determinate locations in visible space if RM doesn’t have the capacity to experience determinate locations at all.

     

    References

    Block, N. (2014). The Puzzle of Perceptual Precision. In Open MIND. Open MIND. Frankfurt am Main: MIND Group.

    Cohen, M. A., Dennett, D. C., & Kanwisher, N. (2016). What is the Bandwidth of Perceptual Experience? Trends in Cognitive Sciences, 20(5): 324-335.

    French, C. (forthcoming-a) Object Seeing and Spatial Perception. To appear in Phenomenal Presence, edited by Fabian Dorsch, Fiona Macpherson & Martine Nida-Rumelin, Oxford University Press.

    — (in preparation). Bálint’s Syndrome and the Structure of Visual Experience.

    Martin, M.G.F. (1992). Sight and Touch. In The Contents of Experience, edited by Tim Crane. Cambridge: Cambridge University Press, pp. 196–215.

    — (1993). Sense Modalities and Spatial Properties. In Spatial Representation: Problems in Philosophy and Psychology, edited by Naomi Eilan, Rosaleen McCarthy, and Bill Brewer. Oxford: Oxford University Press, pp. 206–217.

    Morrison, J. (2016). Perceptual confidence. Analytic Philosophy 57: 15-48.

    Schwenkler, J. (2012). Does Visual Spatial Awareness Require the Visual Awareness of Space? Mind and Language 27(3):308–329.

    Stazicker, J. (2011). Attention, Visual Consciousness and Indeterminacy. Mind and Language 26(2): 156–184.

    — (forthcoming). The Visual Presence of Determinable Properties. To appear in Phenomenal Presence, edited by Fabian Dorsch, Fiona Macpherson & Martine Nida-Rumelin, Oxford University Press.

  2. What role does the representation of space play in our capacity to visually perceive objects? Could empirical data ever settle the matter?

    Chomanski argues that the set of results produced by a number of experimenters examining the visual deficits of Balint’s syndrome patient RM show, pace Schwenkler (2012), that RM does represent space, albeit in an impoverished way. I find the paper to be bold and interesting, and it raises a host of questions, only some of which I’ll have a chance to raise.

    Chomanski frames his argument in terms of the “Kantian thesis that visual awareness of space is required for visual awareness of objects” (p. 8). While, there are obvious connections to Kant’s claims in the Critique, there is a difference between having an a priori representation of space and being visually aware of space. Moreover, Chomanski switches between ‘visual awareness of space’ and ‘representation of space’. What’s not clear to me, therefore, is what he takes to be at stake here. This obviously matters if we are to be able to assess whether RM satisfies a purported condition on visual perception. RM might not be visually aware of space, but might still have an a priori representation of space. Or, RM might be visually aware of space understood in some particular way, but not in the way that we thought was required for visual perception.

    So, one initial question is this: assuming that his interests are not purely that of understanding RM’s condition, which version of the Kantian thesis is Chomanski interested to defend, and why?

     

    Chomanski’s positive claim is that RM’s visual experiences have indeterminate spatial content, but that indeterminacy about location does not equate to a complete absence of awareness of space. The suggestion is an appealing one, but one that I think raises many further questions, some of which I’ll try to elaborate in the rest of my commentary.

    Say that I am looking at a rabbit and a hare, both of which are in front of me. I blink, and in that moment, the rabbit shifts a fraction of an inch. Let’s grant that the two visual experiences—my experience before I blink and my experience after I blink—are phenomenally indistinguishable from one another. That is, given the distance that the rabbit and hare are from me, and from one another, and given my visual acuity, it’s not possible for me to tell that the rabbit has moved. I’ve added a hare, for reasons we’ll come to shortly.

    Chomanski says about this kind of case: “if two experiences of objects which are in fact at different locations are phenomenally indistinguishable with respect to the objects’ experienced location, then the experience is indeterminate with respect to location” (p. 3). So, my experience of the rabbit at t1—when it is in fact at location L1—is phenomenally indistinguishable from my experience of the rabbit at t2—when it is in fact at location L2. The content of my two experiences is indeterminate with respect to locations L1 and L2. This is a version of Siegel’s (2006) case, which Chomanski employs to show that we should allow for some ‘small-scale’ indeterminacy in the spatial content of normal visual experiences.

    One way we might interpret Chomanski’s suggestion about indeterminacy, then, is that RM’s experiences are indeterminate with respect to much larger regions of space, so RM experiences of objects that are at a much greater spatial separation than our rabbit at t1 and t2, will be phenomenally indistinguishable. My experiences of the rabbit are indeterminate with respect to small regions of space: if the rabbit had shifted as much as an inch, I might have noticed. But, if we should think of RM’s experiences as having indeterminate spatial content, they will be indeterminate on a much greater scale.

    This way of thinking about indeterminacy gives us one way of accounting for RM’s poor performance in tasks that require him to locate one stimulus relative to another stimulus. When RM is presented with the letters ‘X’ and ‘O’ simultaneously on a computer screen, he is at chance in saying whether the ‘X’ is to the left or the right of the ‘O’. According to this understanding of indeterminacy, when presented simultaneously with two spatially discrepant stimuli, RM experiences them to be, in effect, in the same place. There is enough indeterminacy in his experience for these locations to be indistinguishable.

    But there is an alternative way of thinking of indeterminacy, I think, that Chomanski also mentions. He gives the example of hearing on the radio that a bear is outside without having any more precise information about its location. In this case, he suggests, I am aware of the bear as in space—I don’t think of it as existing outside of space—without being aware of its location. That is, I represent it as occupying a determinable, but indeterminate location. And Chomanski suggests we can interpret RM’s case in the same way: “he has a conscious representation of objects (perhaps serially rather than simultaneously) as occupying determinable, but not determined, locations in space, perhaps against some undifferentiated background” (p. 5). On this way of talking about indeterminacy, it’s not clear we should think of it as variable. Rather, spatial content is wholly indeterminate, although objects are represented as having determinable locations. And on this way of thinking about indeterminacy of content, RM doesn’t experience the letters ‘X’ and ‘O’ to be in the same place. He doesn’t experience either of them as having any determinate location, merely a determinable one.

    How, then, is Chomanski thinking of indeterminacy? Are these two alternative ways in which spatial content could be indeterminate? If so, which way offers the better explanation of RM’s condition and the empirical data?

     

    Related to this, we might also wonder, relative to which spatial relations should we take RM’s visual experiences to have indeterminate spatial content? Chomanski says only that the content of RM’s visual experiences are indeterminate with respect to “most” (p. 2) and “most if not all” (p. 4) spatial relations. Yet, he also suggests that RM’s perception of the location of an object relative to himself must be “in part […] accurate” (p. 7), given his moderate success in egocentric localization tasks. RM is above chance in performing reaching tasks and in using egocentric terms to localize a single object (Baylis & Baylis 2001).

    It seems therefore that Chomanski’s account depends on it being possible for experiences to have varying degrees of determinacy and indeterminacy with respect to different spatial relations. To what extent, though, does indeterminacy with respect to one spatial relation constrain indeterminacy with respect to other spatial relations?

    In normal vision, I am usually aware of the location of the things I see with respect to both myself and to other things that I see: visual experiences can have egocentric spatial content and allocentric spatial content. Let’s return to the case in which I am looking at a rabbit and a hare. We’ve granted that this is a case in which my experiences of the rabbit are indeterminate with respect to locations L1 and L2. But, is the content of my experience indeterminate with respect to these locations relative to myself only? Or is it indeterminate with respect to those locations relative to the location of the hare only? Or relative to both?

    If the experiences are truly phenomenally indistinguishable, then I am unable to discriminate any difference in the location of the rabbit. So, any reason we have for positing indeterminate content in this case will apply relative to all spatial relations that are represented. Here we have a case in which indeterminacy in egocentric spatial content seems to go hand in hand with indeterminacy in allocentric spatial content.

    That’s not to say that there are not other cases in which the two seem to come apart. As another example of indeterminacy in experience, Chomanski describes a case in which you hear two people speaking while you have your eyes closed, and in which “you can’t tell who’s to the right of whom. That is, you seem to perceive two objects without being able to perceive how they’re spatially related to one another” (p. 3). Of the example, Chomanski says that my experience of the spatial relation between the speakers is wholly indeterminate. Yet, we might still think that in such a case I can be aware of the speakers as being, say, to the left, in that direction. So, it seems to be a case in which content is indeterminate with respect to some, but not other, spatial relations. Or at least, that the degrees of indeterminacy differ with respect to different spatial relations.

    Is this how we should think of RM’s visual experience? One reason that it seems prima facie problematic to extrapolate from audition to vision in that way—even the vision of neurological patients—is that there seems to be substantial differences in the role that space plays in the two modalities, both informationally and experientially. While there are multiple cues to the egocentric location of sound sources that are typically available in audition, this information is not required for the simultaneous grouping of frequency components that determine the sounds that we hear (Nudds 2009). By contrast to the auditory system, which is organised tonotopically, the visual system is organised topographically. That is, the location of neurons within map-like neural structures carries spatial information about the location of objects. If I count as seeing two objects at the same time, then, it seems that I’ll have some awareness of their spatial locations relative to one another, and in particular, that they are not spatially coincident.

    What might be crucial to Chomanski’s argument here is that one symptom of Balint’s Syndrome is simultanagnosia: the inability to see more than one object at a time (Robertson 2003). If RM can only see one Roman letter at a time, then of course he doesn’t see where the ‘X’ is relative to the ‘O’. But then, it’s not clear what sense can be made of the idea that the spatial content of his visual experiences with respect to allocentric relations is indeterminate, as opposed to non-existent.

    However Chomanski’s focus, at least in the latter parts of the paper, is on the egocentric spatial content that seems to be available to RM. Even if RM doesn’t experience allocentric locations at all, Chomanski will, I take it, still say that he counts as perceiving space in virtue of being visually aware of the egocentric location of an object. Chomanski’s reasoning here is that RM must at least be representing the location of the letter on the screen relative to himself, one other object. My final question concerns this claim. On the one hand, we might query whether RM is, in any sense aware of the space between himself and the object he sees. On the other hand, we might wonder whether egocentric contents represent the location of the perceiver at all, or whether instead they should be understood in monadic terms, such as ‘to the left’ and ‘to the right’ (Campbell 1994). What grounds, then, are there for saying that the perception of the egocentric location of a single object is sufficient for visual awareness of space?

     

     

    References

    Campbell, J. (1994). Past, Space and Self. Cambridge, Massachusetts: MIT Press.

    Chomanski, B., Visual Spatial Awareness Probably Requires Visual Awareness of Space. Minds Online conference.

    Baylis, G. C., & Baylis, L. L. (2001). Visually misguided reaching in Balint’s syndrome. Neuropsychologia, 39(8), 865-875.

    Nudds, M. (2009). Sounds and Space. In M. Nudds & C. O’Callaghan (eds). Sounds and perception: New philosophical essays. Oxford: OUP, pp. 69-96.

    Robertson, L. C. (2003). Binding, spatial attention and perceptual awareness. Nat Rev Neurosci, 4(2), 93-102.

    Schwenkler, J. (2012). Does visual spatial awareness require the visual awareness of space. Mind & Language, 27(3), 308-329.

    Siegel, S. (2006). Subject and object in the contents of visual experience. Philosophical Review, 115, 355-388.

  3. 1. Imagine encountering someone who claims that she is visually conscious of the chemical composition of the objects she sees. That is, this person claims to be visually aware, and not merely able to deduce on the basis of visual cues, of which chemical compounds an object is composed of.

    How would we test this claim? Surely a first step would be to give the person the task of identifying the chemical compositions of some objects, perhaps disguising which kinds of objects they were by manipulating ordinary visual cues. This would only be a start, of course: even if the person could do this we’d still need to do a lot more work in order to be confident in her ability and work out some understanding of the mechanisms behind it. But if she couldn’t succeed in this preliminary task then it seems like this would be good reason to suspect that she wasn’t, after all, visually conscious of chemical composition in the way she originally claimed.

    The person might object to this suspicion. And perhaps we could come up with other tasks that would reveal that she did after all have the ability to identify visible objects’ chemical composition, and that this ability was grounded in visual awareness of these features. But what surely wouldn’t satisfy us would be if the person insisted that while she was indeed visually conscious of chemical composition, her awareness of this composition was only indeterminate: that is, that while she always experienced an object as having a chemical composition, there wasn’t a determinate composition that she experienced the object as having. A claim to experience an object as having some-chemical-composition-or-another, with no ability at all to determine which among the many chemical compositions this is, would be empty. That’s because it is hard to see what difference there would be between an experience of an object as indeterminately-chemically-composed and an experience that lacked any representation at all of an object’s chemical composition.

    One thing that concerns me about Bartek’s account of RM’s condition is that it might end up being empty in much this way. On his interpretation RM “has a conscious representation of objects (perhaps serially rather than simultaneously) as occupying determinable, but not determined, locations in space, perhaps against some undifferentiated background.” However, this experience “might represent location broadly enough that little information useful to do well in the experimental paradigm could be extracted from this representation” (p. 5). But what’s the difference between this interpretation and the one I offered in the paper he is discussing, according to which RM’s visual experience lacks any representation of an object’s location and orientation whatsoever? What would it be to have a visual experience of an object as having some-location-or-another and some-orientation-or-another, with no ability at all to say which location and orientation these are? What would make the claim to have such an experience—which, notably, is not a claim that RM himself makes—more than simply empty?

     

    2. I don’t mean to suggest that there is anything wrong with the idea that the contents of experience—visual or otherwise—can be indeterminate. But it seems that there is a limit to how indeterminate an experience can be, with respect to a given determinable range of values, before it simply ceases to count as representing values from that range. At the very least it seems that the content of an experience needs to restrict somewhat which determinate range a given value falls into: e.g. if the person I imagined above could visually distinguish organic from inorganic compounds, then perhaps (perhaps!) we could start coming around to the idea that her visual experience represented this distinction. More obviously, there is no trouble with the idea that your visual experience represents each of the following letters as some distance apart from the others without specifying these distances exactly:

     

    A                                       B                                        C

     

    If you’re like me, you won’t be able to tell just by looking whether the ‘A’ and the ‘B’ are same distance apart as the ‘B’ or the ‘C’, or whether the distances between these pairs are different. (In fact the ‘B’ and ‘C’ are slightly farther apart.) But that’s no barrier to saying that you visually represent these distances; it only suggests that these visual representations don’t have sufficiently determinate values for you to make these fine-grained discriminations on the basis of them. It would be different, though, if you couldn’t ever use vision to judge how far apart things were, or whether the distance between one pair of things was more or less than the distance between another pair. At this point we’d begin to lose our handle on the idea that you had a visual experience of relative distance at all—which, I think, is just what should happen as we consider the full range of RM’s visuospatial deficiencies.

     

    3. Of course there is something really weird in the idea of having a visual experience objects, and their intrinsic spatial properties, though not as positioned in a surrounding space. In this way, RM’s case is the inverse of the one I imagined above: whereas we’d need significant experimental evidence before coming to the judgment that a person did have visual awareness of an object’s chemical composition, we’d need similar evidence before agreeing that someone didn’t have visual awareness of an object’s position in space. Moreover, it makes sense in each case for there to be a default presumption in favor of ascribing the kinds of experiences that we can make sense of having. And Bartek suggests that his account of RM’s condition is in line with this approach: as he notes, we do have visual experiences with indeterminate spatial content, and so it seems sensible to use this as a model for understanding what is going on in RM’s case.

    I’m not sure, though, that Bartek’s appeal to visual indeterminacy really ends up making RM’s condition any easier to imagine on his account than it is on mine.  Consider the thought experiment from Wittgenstein’s Philosophical Remarks that I discussed in my paper as a way of motivating the Kantian view of visual space that Bartek’s paper defends:

    If every point in visual space is marked out as distinct, then there is certainly a sense in speaking of here and there in visual space … But is this property of having points marked out as distinct really essential to visual space; I mean, couldn’t we imagine a visual space in which we could perceive only certain spatial relations but no absolute position? That is, could we picture an experience so? In something like the sense in which we can imagine the experiences of a one-eyed man? – I don’t believe we could. For instance, one wouldn’t be able to perceive the whole visual field turning, or rather this would be inconceivable. How would the hand of a clock look, say, when it moved around the edge of the dial? (I am imagining the sort of dial you find on many large clocks, that has only points on it, and not digits.) We would then be able to perceive the movement from one point to another – if it didn’t just jump from one position to another – but once the hand had arrived at a point, we wouldn’t be able to distinguish its position from the one it was in at the last point. I believe it speaks for itself that we can’t visualise this. (trans. Aue, sec. 206, pp. 253-254)

    I share Wittgenstein’s sense that we can’t form a mental picture of this sort of experience, though as I argued in my paper I don’t think it follows that a representation of absolute position really is “essential to visual space”. Is it any easier, though, to imagine an experience where the representation of spatial position is radically indeterminate in the way Bartek suggests may have been the case for RM? That is, can we imagine an experience in which there is a visible difference between the first and second, and second and third, of these clock faces, but not between the first and the third, such that we could see the hand moving from the first position to the second, and the second to the third, but then not experience the difference between the final position and the original one? I believe it speaks for itself that we can’t.

     

    Image of three circles, each with four quadrants, and each with an arrow pointing to different parts of the the same quadrant.

    Given this—given, that is, that visual experiences with the relevant sort of radically indeterminate spatial content are no easier to imagine than ones in which there is no visual representation at all of absolute space—I don’t think that Bartek’s account should be favored over mine on these grounds.

     

    4. I’ve not said anything here about the evidence Bartek discusses in the final sections of his paper, which seems to suggest that RM did indeed have some experience of objects’ spatial position. That’s mostly because I’m not confident that there is much in there to disagree with. (Perhaps that will change down the line.) I want to observe, though, that the pressure there against my argument comes from just where I think it should: namely, from experimental data that seem to favor interpreting RM as possessing a conscious visual representation of space, rather than phenomenological argumentation showing that this must have been so, since otherwise his experiences would be of an unimaginable kind.

     

    5. I’ll close by saying something that perhaps should have come at the start: I’m really grateful to Bartek for writing this paper. It was really gratifying to have my work engaged with in such a clear and careful way. I hope he feels similarly about my commentary.

  4. I am very grateful to Robert Briscoe, Alisa Mandrigin, and John Schwenkler for taking the time to write their thoughtful, challenging, and engaging commentaries on my paper. They raise a host of good points and I hope to be able to address at least some of them in this reply. I would also like to thank John, Nick Byrd, and Cameron Buckner for all the hard work they put in organizing this conference. It’s a pleasure to be a part of it.

    I will discuss Robert Briscoe’s comments first. Briscoe raises two worries about the interpretation of RM’s condition that I commit myself to, and the conclusion I draw from it. For starters, Briscoe is skeptical of whether the interpretation of RM’s condition according to which RM represents objects’ locations in a maximally indeterminate way does satisfy the Apriority Thesis (AT). The reason why is that even if we accept that RM represents locations indeterminately, his experience need not be structured by the visual field. Briscoe claims, however, that AT is best understood as entailing that visual experience involves a visual field. I take it that the reasoning used could be approximated in the following way:

    (1) If AT is true, then RM’s visual experience involves a visual field.
    (2) RM’s experience doesn’t involve a visual field (even on the maximal indeterminacy interpretation).
    (3) So, AT is not true (even on the maximal indeterminacy interpretation).

    Now, it seems to me that it’s premise (2) that shows the most potential for being challenged. Briscoe supports it by appealing to Craig French’s paper on RM (http://craigafrench.github.io/assets/CFBalintsPaper.pdf). In that paper, French defends a different way of making sense of RM’s experience (roughly, that RM does see objects as in space, but the space exactly coincides with the object seen—it is what French calls “object space” and it’s not experienced as a larger framework within which the object is located), and he also gives an argument for premise (2).
    On French’s view, one he adopts from Louise Richardson and Matthew Soteriou, to have a visual field is to have a sense of certain sensory limitations manifest in visual phenomenology: in normal visual experience, “it seems as if I can only see so much, and that there is more to be seen beyond what I can now see. This can be specified in spatial terms, in terms of the boundaries of the space delimited by the visual field: I can be aware only of what falls within a space of such-and-such a size and shape. I have a sense that some way over to the left, for example, at the limit of the cone delineated by the visual field, there is a boundary I cannot now see beyond. But I have a sense of there being more, waiting to be seen if only I alter my point of view” (French, in preparation).

    And then French argues that this sense of limitations-as-my-sensory-limitations present in normal visual experience is lacking in RM (to be more precise, the claim is that, given that French’s interpretation of RM is right, this is a consequence of that interpretation).

    I think that French’s argument could be challenged on its own terms, that is, even accepting the interpretation of RM he proposes. French writes, “In seeing an object the space RM sees is at most the relevant object-space, not a cone of physical space in which he can locate the object, and see it as spatially related to other things and spaces. Thus the experiences RM is capable of having differ from typical visual experiences which involve a visual field. And suppose RM sees an apple. RM sees the apple and the apple-space. RM can be aware only of what falls within the apple-space he sees. But this limitation is set by the apple he sees, and its spatial structure. If RM goes from being aware of the apple, to being aware of, say, a church, or a banana, the way in which his experience is limited will change accordingly. The spatial specification of the limitation will now be set by the spatial structure of the church or the banana. This is quite unlike how things are in experiences which involve a visual field. It is not that the limits imposed by the visual field can’t change, but that such changes, if they do occur, are not set by changes in objects one is aware of, but by one’s sensory limitations.” (ibid.)

    I think, however, that it is possible to have an ordinary visual experience where the visual field’s limitations are set by the space one is in, e.g. when sitting in a windowless, empty room whose walls begin to contract or expand. Or, imagine a human being with a normal visual system that gets transported every once in a while to and from windowless, empty rooms of different shapes and sizes. I want to claim that such a being would have a visual field but that its limitations would be set by the space one is in, by the object one sees. It isn’t therefore as clear that we’ve been given enough reason to accept that RM lacks a visual field. French’s argument for premise (2), then, can be resisted.

    Is there any reason to think that RM’s visual experience involves a sense of space as extending beyond the boundaries of the visible, that his own sensory limitations have some phenomenological salience in experience? I’m not sure; and it’s unclear to me how to test it. But I think that Briscoe’s point is very helpful in bringing out the connection between AT and the visual field in Robertson’s and Soteriou’s sense. I agree that involving this sense of space as extending beyond the boundaries of the visible might be one of the ways in which an experience might meet AT’s constraints. And secondly, it is probably the only way in which it can be met for simultanagnosics like RM. But I’m not sure that we can be confident that RM’s experience lacks this feature.

    Briscoe’s second point concerns the thesis that RM’s experience involves maximally indeterminate spatial content. He writes: “RM’s visual experience can’t represent an object’s location as falling somewhere within a maximally wide range of determinate locations if RM, by hypothesis, is not capable of representing the determinate (egocentrically or allocentrically specified) location of any object. Similarly, experiencing a probability distribution with respect to an object’s location in space presupposes, I take it, an intact capacity to represent the different possible locations at which the object might be situated. It doesn’t make sense to say that RM’s perceptual confidence concerning an object’s location is low for all possible determinate locations in visible space if RM doesn’t have the capacity to experience determinate locations at all” (Briscoe, Comments).

    I take the objection to be something like this: to experience an object as located indeterminately with respect to some locations, L1, L2, L3, it is necessary to represent L1, L2, and L3 determinately (let’s call this the Indeterminacy Constraint, or IC). RM lacks the latter capacity, so he fails to meet IC, and thus can’t experience objects as indeterminately located.

    Is IC a constraint on visual representation, perceptual representation, or spatial representation in general? It is not clear; but suppose it’s the middle option. Here, there might be cases in which it fails to apply, and yet the experience would have indeterminate content; consider the hearing example I relied on in the paper: when I hear two people A and B talking in the next room, without seeing them, I can tell that they’re both to my right without being able to tell how exactly they’re arranged with respect to one another. Now, if you asked me, which one of them is closer to the copying machine, also in that room, I won’t be able to tell you. But it doesn’t mean that I am determinately representing some particular locations in the room and fail to assign A’s and B’s locations to any of them. I’m just not aware, in my experience, of any phenomenal difference with regard to location properties between A’s voice and B’s voice (or between where they’re coming from). At least, I don’t think that’s what my experience is like. Suppose this is right about the auditory case, is it legitimate to extend such an approach to the visual case? Serious questions could be raised here (see, in particular, Mandrigin’s comments above).

    Perhaps another way to circumvent the difficulties raised by clarifying the exact nature of indeterminate experience in RM would be to say that RM only detects location in terms of topological properties, such as being outside, while being unable to detect other kinds of spatial properties such as direction or distance. The visible object would thus be experienced by RM to be at a location without appearing to be at any distance or direction. RM’s experience could then be described as determinate with respect to topological spatial properties, while remaining indeterminate with respect to such properties as distance and direction.

    I will now move on to discussing the points raised by Alisa Mandrigin. In response to the question regarding the clarification of the kind of thesis I’m interested in defending: My aim, in general, is to defend the view that RM has some form of visual awareness of space, though my formulation has indeed been sloppy. I take the broader significance of this thesis to cast doubt on the view that RM’s experience falsifies what John has called “Apriority Thesis”: “it is impossible for there to be spatial perception (i.e. perception of spatial objects, properties, and relations) without the awareness of space (i.e. ‘space in the strict sense’, or an overarching and somehow ‘absolute’ space within which everything is perceived as situated).” I merely wanted to offer an interpretation of RM’s condition that doesn’t require us to give up AT.

    When it comes to clarifying the kind of indeterminacy I take RM’s experience to exhibit, I think the best way to characterize it would be in terms of varying indeterminacy, where the most extreme cases (i.e. the ones that Schwenkler’s argument rests on) can be understood as involving indeterminacy relative to all kinds of relevant spatial relations except something like the topological relation of being outside (in other words, RM could determinately represent the object to be out there; but still represent its direction and distance indeterminately).

    I agree, therefore, that “[my] account depends on it being possible for experiences to have varying degrees of determinacy and indeterminacy with respect to different spatial relations” (Mandrigin, Comments), and I agree with much that follows. In particular, I do think that we should think of RM’s experience as involving “content [that] is indeterminate with respect to some, but not other, spatial relations” (ibid.).
    I wholly concede the point regarding the description of the auditory example I have given in the paper. Mandrigin is right to describe it as one where “I can be aware of the speakers as being, say, to the left, in that direction” (ibid.). I also agree that the differences in spatial processing between vision and audition are definitely worrisome for the analogy I’m drawing between sight and hearing. But perhaps a similar example could be found within vision itself: e.g. think about detecting motion in your peripheral vision without being able to identify its direction. In such a case, my experience would represent the motion as, say, occurring on my left, without representing how the starting location and the ending location of the movement are related. So it might be that I need not rely on cross-modal comparisons to make this point.

    I also concede that, given RM’s simultanagnosia, the discussion of the ability to represent allocentric spatial properties is, to a large extent, moot.

    When it comes to the egocentric content that might characterize RM’s experience, it’s true that I have assumed it to be relational rather than monadic. But even supposing that egocentric spatial contents are monadic, I still think that the ability to see something as on the left, as opposed to it being on the right or in the center, does suggest the ability to see the object as within a larger space, a space that includes the center and the right as well as the object’s actual location. And this could be true even if RM fails to see the space between himself and the object.

    I will now discuss the commentary by John Schwenkler. Schwenkler begins by raising questions concerning the difference between saying that RM represents objects’ locations in larger space maximally indeterminately and not representing them at all. In one, perhaps rather unsatisfactory sense, the differences are not to be found in the empirical predictions that the two interpretations would generate, but rather in the philosophical commitments regarding the nature of visual experience that one challenges and the other is consistent with. A more substantive reply, however, can also be given, I think. (It’s inspired by what Schwenkler writes in section 2 of his commentary).

    Suppose we all agreed there are some experiences that don’t have any spatial phenomenology (and so, they do not represent any locations in larger space); and suppose we also agreed which (kinds of) experiences these are (perhaps conscious thought; or a conscious mood; or some instances of auditory experience). Perhaps some experiment could be designed that would test whether a Balint’s syndrome patient responds differentially to localization tasks that involve these non-spatial experiences, and the tasks that involve the localization of visual stimuli. To give a toy example: suppose we agree that conscious thought has no spatial phenomenology; if RM reacted differently to tasks requiring him to identify where his thought seems to be located than to tasks requiring him to identify where a seen object is located, this would give support to my interpretation over Schwenkler’s. If there was no relevant difference, this would favor Schwenkler’s interpretation over mine. There are, to be sure, obvious difficulties with pretty much every aspect of this setup. But I think the example shows that at least it doesn’t appear impossible to come up with a situation where our interpretations generate different predictions.

    I think I have to agree with John’s third point. On reflection, it does appear that my interpretation doesn’t make it any easier to imagine what it might be like to have Balint’s syndrome than John’s. Objects seen in our peripheral vision do, after all, appear either on the left or right; their locations are by no means entirely indeterminate.

    Lastly, I just want to reiterate that I’m really grateful both to the organizers of this conference for giving me the opportunity to present my work here, and to all the commentators for their time and effort in discussing the ideas I put forward. It really is a gratifying experience.

    I’m sure there are many issues left open by my replies, and I’m looking forward to further discussion.

  5. Hi Bartek,

    Thanks for this reply. One possible way to develop your suggestion in the penultimate paragraph: we might consider the phenomenon of “hearing voices” (or other sounds) when they don’t seem to be coming from anywhere in the outside world. Sometimes we say that these sounds are “in our heads”, but I doubt whether that should be taken literally, or as an accurate description of the sounds’ phenomenal character. They seem instead to be located nowhere, or nowhere indeterminate. It would be fascinating to ask RM whether his visual experiences are (or were) like that. Can you think, though, of further ways that we might probe that experimentally, i.e. beyond just asking him for a subjective characterization? Or were you thinking that such a characterization is the best we could do here?

    Thanks,
    John

    1. Hi John,

      Many thanks for your comment. I think you’re right, hearing voices is certainly a plausible candidate for a non-spatial experience. I’ve also been worrying about the possible ways to examine experimentally the potential difference between RM’s cognitive phenomenology and visual phenomenology, but I haven’t been able to come up with anything that could test it, aside from asking for a report.

      That said, while I’m not sure if the following experiment would demonstrate that RM’s experience is spatial, it would certainly be suggestive. In the paper I have cited by Phan et al. the authors discover that RM is susceptible to the sort of reverse ventriloquist illusion; that is, the localization of visual stimuli is influenced by the localization of simultaneous auditory stimuli (auditory localization in RM dominates visual localization; the proposed explanation is that spatial information regarding the location of stimuli is more specific in RM’s audition than it is in his vision).

      Now, I think a case can be made that in order for RM to exhibit this “auditory capture” effect, he must have experienced the visual stimulus as being in space in some unspecified way, so that the perception of the visual stimulus could be influenced by a more specific auditory spatial stimulus. If RM’s vision did not represent objects as located at all, why would the auditory spatial cue make any difference to how (and, specifically, where) the visual stimulus gets experienced?
      Now, the experiment was carried out some years after the ones you’re discussing in your paper, so it’s not strictly relevant to my original case, but if auditory capture had been observed in RM then, at the time of the original experiments, I think it could give us some reason to think of RM’s spatial experience at that time along the lines I propose.

      1. Oh that’s a really cool finding! Thanks for making me aware of it. Of course it’d be tricky to tease out whether the kind of visual spatial representation required for that is conscious or unconscious (cf. the discussion of RM and the Stroop effect in my and John Campbell’s papers). But I agree with you that it’s suggestive, for sure.

  6. I hope you can keep this discussion going. Some random ideas: Can you sketch, model or film something akin to the experience you’re arguing for? Can you also imagine it (e.g. by recourse to dream or other incomplete states)? How might your discussion develop in a multidisciplinary setting? How many bodily processes/systems are under discussion and how are they implemented – recognition, motor control/coordination, verbal report, memory, ego/allocentric spatial representation, multimodal integration, colour, brightness, edge detection etc, stereoscopic vision, field of view, eye/head movement, balance/orientation, etc (I don’t know!) – and in what proportion are they affected by the condition; does any change in the nature of extent of a patient’s condition, responsiveness to therapy or adaptation to the condition give any clues as to what systems are being affected and in what way? You all raise many of these points – which was stimulating for me, but then slightly unsatisfactory as I couldn’t picture your positions concretely as an overall thing.Thanks, Pablo

  7. P.S. Experiments (like the clock example, or church vs banana space) – what is an object, how are its spatial characteristics represented? Are the letters G and P two objects, only capable of identification or location one at a time, but can the letters GP butted up to one another without a gap become a single object that can then perhaps be identified as two letters in a particular spatial order? That question is both generally for most people and for someone like RM with a specific condition. What other (thought/real) experiments would help?
    P.P.S. Think I also forgot summary statistics in my earlier comment – what kinds are available, from which systems, within different task or experience settings?
    Cheers, Pablo

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