111

Sue Ned Block!: Making a better case for P-consciousness doi: 10.1017/S0140525X07002920 Victor A. F. Lamme Department of Psychology, University of Amsterdam, 1018 WB Amsterdam, The Netherlands. The Netherlands Institute for Neuroscience, part of the Royal Academy of Arts and Sciences (KNAW), 1105 BA Amsterdam, The Netherlands v.a.f.lamme@uva.nl www.cognitiveneuroscience.nl Abstract: Block makes a case for the existence of conscious experience without access. His case would have been much stronger, however, if he had woven fully unconscious processing into the “mesh argument,” and considered arguments that are intrinsic to neuroscience. Sometimes, science looks like a court of law. There is a scientific hypothesis– the defendant– and there are its advocates and opponents– the defense and prosecution. Here, the defendant is conscious experience. It stands accused of not existing in its own right. Conscious experience is what we say we see or hear, what we cognitively access and manipulate– so claim the prosecutors. Ned Block is leading the defense team, arguing that we should not equate conscious experience with cognitive access. Many psychological experiments show mental representations that have higher capacity than what is reported by the subject. These mental representations have phenomenal qualities and might just as well be conscious representations. There is sufficient evidence to cast reasonable doubt on the accusation. Should the defendant be satisfied with such a defense, or litigate for malpractice? I think the latter. Block has made only half a plea (his “mesh argument” lacks a key consideration), and left out all the forensic evidence (arguments intrinsic to neuroscience). Neurophysiologicalstudiesinprimates(Supe retal.2001b),aswell as electroencephalography (EEG) (Sergent et al. 2005), functional magnetic resonance imaging (fMRI) (Haynes et al. 2005), and transcranial magnetic stimulation (TMS) (Silvanto et al. 2005b) studies in human subjects, show that recurrent or re-entrant processing between different regions of the brain is necessary for conscious experience. In the Global Workspace theory (GWT) (Baars 2005; Dehaene et al. 2006), the content of information processed in, say, visual areas, is broadcast and made available for global access by means of recurrent amplification. “Workspace neurons,” in prefrontal cortex, are vital to this amplification, because they provide 511 BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh Figure 1 (Lamme). Three stages of visual processing: First, visual information is processed along the sensorimotor hierarchy (V1 to M1) by means of feedforward connections. This constitutes the feedforward sweep (I1). Depending on attention, subsequent recurrent processing either remains localized to visual areas (V1, V4, IT; I2) or extends towards areas involved in the planning and execution of movement (PFC, M1; I3). Phenomenal sensation develops from I1 (unconscious), via I2 (P-conscious), to I3 (A-conscious). See Lamme (2003). long-range connections between sensory and motor cortices. With global recurrent amplification, conscious experience becomes accessible and reportable (Sergent et al. 2005). However, more localized recurrent interactions, restricted to visual areas and not involving specialized workspace neurons, are also possible and have been reported (Scholte et al. 2006). Advocates of GWT argue that in that case there is noconsciousexperience, onlyproto-consciousness,precisely because of the absence of global workspace (prefrontal cortex) activation. Block, however, argues that such localized recurrent states correspond to phenomenality without access. He converges upon that view through the “mesh argument”: If we assume that the neural basis of phenomenality (recurrent processing in visual cortex) does not include the neural basis of access (frontal cortex), we can understand why phenomenality overflows access, as is shown in the Sperling, Landman et al., and Sligte et al. experiments. Although I agree with the conclusion– localized recurrent processing is conscious processing– this is an argument that I suspect will convince only part of the jury. The metaphysical correlationist can sketch a competing mesh argument, interpreting the iconic memory experiments as nonphenomenal, proto-consciousness overflowing “real” consciousness. And he would argue that this corresponds to the difference betweenprocessing with or without workspace neuron activation. No need for acquittal of the defendant. The epistemic correlationist would still find both options not scientifically distinguishable. Call for a mistrial. What we need are independent arguments for attributing phenomenality to localized recurrent processing. The mesh argument should not only take the division between local and global recurrent processing (I2 and I3 in Dehaene et al.’s [2006] terms, Fig. 1) into account. The issue becomes much clearer when fully unconscious or inaccessible neural processing (I1) is alsoconsidered. Since there is little disagreement about the absence of conscious experience in I1,oraboutitspresenceinI3, the question becomes whether I2 is more like I1 (i.e., unconscious) or like I3 (conscious). This is an empirical issue. The question could be asked, whether properties we usually associate with conscious percepts (I3) are also present in iconic memory (I2), or in other alleged cases of inaccessible experience (attentional blink, neglect, split 512 brain– probably all I2). For example, unconscious processing (I1 in the neural sense) is typically about feature extraction, whereas in conscious perception (I3) features are combined into objects, backgrounds, and so on (Lamme 2004). Is there perceptual binding in iconic memory (Landman et al. 2003)? Do indirect effects (such as learning) of I2 states operate along the dimensions of isolated features or of coherent percepts? Similarly, it could be asked what the critical neural differences are between I1,I2,andI3 states. The first 100 msecs of visual processing is dominated by feedforward activation of the brain. Information sweeps from visual to frontal areas, not accompanied by conscious experience– that is, fully inaccessibly (I1) (Lamme& Roelfsema 2000). Subsequently, recurrent processing is instantiated by horizontal and feedback connections.Withtime, localized (I2) recurrent cores may grow into more global ones (I3), depending on bottom-up and top-down selection mechanisms (Lamme 2003). Where does the critical neural dichotomy lie? Between feedforward and recurrent processing– that is, between I1 and I2/I3, as Block and I would argue (Block 2005; Lamme 2003)– or between I1/I2 and I3, as GWT advocates try to let you believe (Dehaene et al. 2006)? Before you choose, please consider that also in fully unconscious feedforward activation (I1), there is activation of workspace neurons, as is shown by masked stimuli activating prefrontal cortex (Lau & Passingham 2007; Thompson & Schall 1999). In addition, there are important differences in the properties of feedforward versus feedback synapses. It is likely that feedforward activation is not mediating synaptic plasticity and learning, while recurrent processing (of whatever extent) does do so (Singer 1995). Third, recurrent processing between visual areas has been shown to mediate perceptual organization, binding, and figure-ground organization, in cases of inattention andthe absenceof report, as well, whereas feedforward processing is typically about feature extraction and categorization (Lamme 2004). Finally, recurrent processing is suppressed by anesthesia, whereas feedforward is not (Lamme et al. 1998). To the neuroscientist, it therefore seems pretty straightforward to draw a line between feedforward processing (I1) ontheone hand, and recurrent processing (I2/I3) on the other. Of course, the extent of these recurrent interactions matters: when frontal or motor areas are involved, a report is possible, otherwise not. But that also applies to feedforward processing. Unconscious behavioral effects (like priming) are possible only when the feedforward sweep penetrates deeply into the sensorimotor cascade. The key feature “causing” phenomenality in I3 states therefore seems to be the recurrency, not the activation of workspace (frontal) neurons. Occam’s razor thus obliges us to group I2 with I3, notwithI1, and to attribute phenomenality to both I3 and I2. The neuroscience angle brings that out immediately, and much more convincingly (Lamme 2004). The jury can now go out and deliberate. Can we equate iconic memory with visual awareness? doi: 10.1017/S0140525X07002932 Rogier Landmana and Ilja G. Sligteb aMcGovern Institute for Brain Research, Massachusetts Institute of Technology, Cambridge, MA 02139; bDepartment of Psychology, University of Amsterdam, 1018 WB Amsterdam, The Netherlands. landmanr@gmail.com i.g.sligte@uva.nl Abstract: Every time we look around we can see a rich and detailed world surroundingus.Nevertheless,themajorityofvisualinformationseemstoslip out of ourthoughtsinstantly. Canwestill say thatthis fleeting percept of the entire world was a conscious percept in the first place, as Block proposes? Attention enables human observers to report and to remember visual information. However, in our experiments, the formation of the memory trace that gives rise to the partial report benefit BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh takes place without focal attention being directed to the items while they are in view. After the items have disappeared and the cue appears, focal attention shifts to the cued item in memory and enables observers to make a large amount of information available for report. This suggests that much more information is processed beyond the scope of focal attention. The properties of the iconic representation indicate that the items in the scene have undergone more extensive processing than one might expect given that no focal attention was directed at them. We have shown that a cue allows for recovery of multiple features of the same object, indicating that feature binding has taken place, and objects are at least processed up to the level of f igure-ground segregation (Landman et al. 2003; 2004); characteristics that historically were only attributed to attentional– that is, reportable– stages of visual perception. In addition, iconic representations can last up to several seconds, and they are not a mere after-effect (Sligte et al. 2008). Also, several older studies have already indicated that iconic memory has a spatiotopic component, suggesting that it has undergone more processing than if it were strictly retinotopic (e.g., Breitmeyer et al. 1982; McRae et al. 1987; for a review, see Cowan 1995). In daily vision, and in most experiments, when new information enters the visual cortex, the processing of that information gets priority over keeping information about stimuli that are no longer there. In the iconic memory experiment, we limit the entry of new information by showing a blank screen after the stimuli presentation. This allows us to test how much information about the stimuli is available in the visual system, by cueing one of them. If there is a distinction between phenomenal awareness and access awareness, then iconic storage can be seen as a window into the contents of phenomenal awareness. This is difficult to achieve in another way. If we test while the stimuli are still in view, subjects can just get information by looking, or switching attention, whereas if we test once new stimuli have already appeared, the processing of those new stimuli interferes with information we were interested in in the first place. Iconic memory may be so vulnerable to interference that even the subjects’ own response interferes with it. Many classic iconic memoryexperiments requireda verbal response and identification of items. It could be that while the subject was reporting items, the report itself interfered with memory. Our experiments, however, merely required a “yes/no” button press, and change detection instead of identification of the items. Thus, the “report” requirement was much smaller, while we could still get an estimate of the amount of information available. That could be a reason why cues in our experiments are effective up to several seconds after stimulus offset, longer than in a classic iconic memory experiment. Another major difference is that in standard partial report designs, subjects are shown a brief sample display just once before reporting about them, whereas we employed a match-to-sample design. Thus, in our design all items are shown twice; once during encoding and once during report. It seems that memory in general (including other forms of memory, such as long term memory) does better on recognition than on recall. In favor of Block’s proposal, studies so far indicate that iconic memory does not have the key properties of an unconscious process, while it does have properties typical of a conscious process. Unconscious processes (such as masked representations) typically remain inaccessible even when attention is focused on the specific object of interest, whereas iconic memory is accessible when cued. Also, in unconscious processing, even basic features may not be processed to the level of perception. Recent evidence shows that unconscious color-priming effects are more dependent on physical stimulus properties than on perceptual properties (Breitmeyer et al. 2004). In iconic memory, however, not only have features been resolved, but also figure-ground segregation and feature binding have already taken place, properties that are more associated with conscious processes. Additional ways to find out whether iconic memory has properties in common with conscious processes include neurophysiological studies. In neurophysiology, it is possible to distinguish between feed-forward processing, and recurrent processing (Lamme & Roelfsema 2000). By selectively disrupting recurrent processing (RP), but leaving feed-forward processing intact, it has been observed that visual awareness does not arise. This was shown by backward masking (Lamme et al. 2002), by applying transcranial magnetic stimulation to the primary visual cortex (Jolij & Lamme 2005; Pascual-Leone & Walsh 2001), and by inactivating higher visual areas (Hupe et al. 1998; Lamme et al. 1998). Even when there are sudden lapses in awareness, it is observed that RP is absent, whereas feed-forward processing is intact (Super et al. 2001b). Many scholars agree that RP is likely to be involved in conscious perception. Current and future experiments are necessary to address what the exact mechanism behind iconic memory is, in which areas of the brain it occurs, and whether RP is involved. However, if there is RP, depending on how widespread it is, views will still differ on whether it looks more like a conscious process or more like an unconscious process. Some argue that RPwithin thevisual cortices is sufficient for conscious perception to arise (Block 2005; Lamme 2003; 2006), while others maintain that consciousness requires more widespread recurrency, including areas involved in cognitive access and control, such as the prefrontal cortex (Dehaene et al. 2006). It is important to test whether RP is involved in iconic memory. Preliminary data provides some indirect evidence for this, by showing a cortical origin and a long-lasting, reverberating nature. Still, more direct evidence is required to determine whether RP takes place and whether iconic processing is necessary and sufficient for visual awareness to occur. Broken telephone in the brain: The need for metacognitive measures doi: 10.1017/S0140525X07002944 Hakwan Lau and Navindra Persaud Department of Experimental Psychology, University of Oxford, OX1 3UD Oxford, United Kingdom. hakwan@gmail.com http://hakwan.googlepages.com nav.persaud@utoronto.ca http://navpersaud.googlepages.com Abstract: The fact that early visual processing has a larger capacity than later visual processing can be explained without positing distinct systems for phenomenology and cognitive accessibility. While phenomenology may overflow forced-choice reports, the later can also overestimate the former, as in the case of blindsight. Metacognitive measures of awareness offer a way to address the “methodological puzzle” of consciousness research. Block claims that sometimes we see more than we can report because the neural system for phenomenology “overflows” the system for accessibility. He makes the additional claim that this implies there are distinct neural mechanisms for phenomenology and cognitive accessibility. We argue that the difference in capacity between phenomenology and accessibility can be explained by noise amplification without any need to posit distinct systems. We explain why we think Block’s approach is unable to build upon empirical findings, and suggest that metacognitive approaches will be more fruitful. As a message passes down the line in the “broken telephone” or “Chinese whisper” game, it becomes garbled and some of its elements are completely lost. That is, the quality of information tends to deteriorate. Noise propagation and amplification also limit late sensory processing in the brain. This is why early forms of vision that are brief and iconic have larger capacities than later verbal reports which require deeper information processing. Simply put, the retina has more visual information for a simple visual perceptual event than the motor cortex. Hence, a 513 BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh difference in capacity is consistent with a single stream of serial processing and does not imply distinct processing systems, as Block claims. Note that our argument does not apply to situations when there are actually two streams of information, as in the dorsal-ventral distinction in visual processes (Goodale et al. 1991). In that case, the two systems are largely independent of each other. In Block’s case though, the later cognitive access certainly depends on and receives its major inputs from the earlier brief processing, and for this reason the capacity difference is trivial. Although we disagree with Block over the explanation of the differing capacities of phenomenology and cognitive accessibility, we agree that forced-choice reports can fail to capture what feels to be seen, especially when there is a lot going on in the visual presentation. This leads Block to propose “a neural mechanism by which phenomenology can overflow cognitive accessibility” (sect. 14, para. 3). But “overflow” is just one example of the failure of forced-choice reports. There are also cases in which forced-choice reports capture more than what is consciously seen. People with V1 lesions claim not to see anything in their affected visual field and yet make accurate visual discriminations; that is, they have blindsight (Weiskrantz 1986). There are other cases in which forced-choice reports made with different modalities (e.g., manual button press, eye blinks, verbal reports) yield inconsistent measures of phenomenology given the same stimulus (Marcel 1993). There are yet other cases in which a stimulus can cause people to make a forced-choice response that they do not want to make (Debner & Jacoby 1994; Persaud & McLeod 2007). So forced-choice reports are not ideal for measuring phenomenology. But this does not mean that we must associate phenomenology with a neural system that has a different processing capacity than that reflected by normal forced-choice reports. Nor does it mean that the capacity reflected by forced-choice reports under optimal cueing conditions (as in Sperling-style experiments) is the capacity for phenomenology. We never know, because forced-choice reports sometimes capture too much, sometimes capture too little, sometimes are inconsistent, and sometimes capture irrelevant information. We suggest that we must explore alternative measures, as it is vital to find reliable and valid ways of measuring phenomenology behaviourally before attempting to map it to a specific brain mechanism. We have been doing just this by employing metacognitive measures (Lau & Passingham 2006; Persaud et al. 2007); that is, we collect subjective reports, or judgements of performance, in addition to forced-choice reports regarding the stimuli. Part of our motivation for using metacognitive measures is demonstrated by how Block’s argument fails to find empirical support where he claims it does. Block claims that recurrent processing (feedback loops; for motion that is V1 ! V5 ! V1) within the visual cortices may support phenomenology. Given the above argument about capacities, it is clear that any processing stage prior to the stage that supports normal reportability would have a capacity large enough to “overflow” cognitive accesibililty, and thus be a good candidate for the supposed phenomenology. The retina, for instance, has all the visual information needed to support what is likely to be seen but not reported. Of course, Block does not think that the retina is a candidate. Presumably the reason is that the retina is not necessary for phenomenal vision: Electrical stimulation of the primary visual cortex can cause visual phenomenology without the retinal involvement. So being necessary for phenomenology is an important criterion. But pure feedforward processing (i.e., V1 ! V5, without the feedback for the case of motion) may fit this criterion as well, and, if one follows the above argument about capacities and inheritance of noise, the information capacity of this processing would certainly overflow cognitive accessibility. Block attempts to support his feedback hypothesis by pointing out that disrupting feedback processing is correlated with a lack of visual consciousness (Pascual-Leone & Walsh 2001). But if Block’s argument that there can be stimuli which a person can 514 see but not report is right, how do we know that in these cases there is a lack of phenomenology (and not just a lack of cognitive accessibility)? Block’s argument backfires: If we allow for phenomenology without access, we would not be able to know when people do not see visual stimuli. For example, when magnetic fields disrupt feedback processing and people report not seeing stimuli they would otherwise see, how can we know that people do not actually see the stimuli? How can we know that feedback processing within the visual cortices does not just reflect cognitive access? Webelieve that using alternative measures of phenomenology, such as metacognitive measures, may fill this gap. Although they may be imperfect, metacognitive measures are the best available method for determining when a person is aware of a stimulus. It is only after awareness can be properly measured that the neural substrates of consciousness can be found. Thus, metacognitive measures avoid the circularity inherent in Block’s approach– that is, the very circularity in the “methodological puzzle of consciousness research” that Block attempts to address. Two kinds of access doi: 10.1017/S0140525X07002956 Joseph Levine Department of Philosophy, University of Massachusetts, Amherst, MA 010039269. jle@philos.umass.edu http://www.umass.edu/philosophy/faculty/levine.htm Abstract: I explore the implications of recognizing two forms of access that might be constitutively related to phenomenal consciousness. I argue, in support of Block, that we don’t have good reason to think that the link to reporting mechanisms is the kind of access that distinguishes an experience from a mere state. Block’s original distinction between phenomenal consciousness and access consciousness has provoked a lot of critical comment in the last decade or so, my own included. I see two distinct sources of uneasiness with the distinction between phenomenal and access consciousness, and while these two sources have not usually been distinguished, some of Block’s remarks in the present target article seem to acknowledge the need to do so. On the one hand, coming principally from a functionalist perspective, many philosophers and psychologists believe that there has to be a constitutive connection between what we are conscious of and what we can report. The idea is that consciousness is somehow reducible to this kind of access, and only if we can so reduce consciousness will it be amenable to scientific investigation. It is this view that is Block’s target here. On the other hand, some, like myself, have been uneasy with Block’s distinction because the idea of phenomenal consciousness totally divorced from any access by the subject does not really seem like any kind of consciousness at all. As Block notes here, we have complained that the very phrase that serves to canonically express the notion of the phenomenal– “what it’s like for x to …”– explicitly refers to the phenomenal state in question being “for” the subject. The way I would put it now is: Phenomenal states/properties are not merely instantiated in the subject, but are experienced by the subject. Experience is more than mere instantiation, and part of what that “more” involves is some kind of access. So one possibility, suggested by Block’s discussion here, is that for a state to be phenomenally conscious it must be accessible to the subject in some sense, but not necessarily to the mechanisms responsible for report. Block supports the view by appeal to the Sperling and the Landman et al. experiments, together with the associated neurological data, which, he argues, show that BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh phenomenal consciousness overflows the “working space” that is report-accessible. Is this appeal persuasive? One thing to notice right away is that Block’s own argument actually relies on building some notion of access into the notion of what is phenomenally conscious, which reinforces the argument mentioned above. After all, in the Sperling experiment, the evidence that is supposed to show that we are phenomenally conscious of more than we can report is that there is information concerning the identity of the letters in the array that we are aware of, though we lose it when reporting mechanisms are engaged. The evidence that it was there in phenomenal consciousness is primarily that we say we saw all the letters. My point is not about the saying, but about the fact that what we report is that we did have a kind of access to this information; and it is because the information is available phenomenally that, when prompted appropriately, we can report a portion of it. But now one might object that we can’t really tell from the experimental data that the identities of the letters were phenomenally conscious. One might claim that, instead, one was phenomenally aware of more generic information, and that the specific information manifested in the partial report was stored unconsciously. Block explicitly addresses the objection that perhaps the information persists retinally only, but one might claim, in response to his demonstration that it goes higher up, that it is still a matter of unconscious, or sub-personal storage. How can one ever rule that out, after all? Of course, Block is not claiming to have a knock-down refutation of his opponents’ interpretation of the data, just a more plausible version. I find myself largely sympathetic to his position, and so wonder about the source of the resistance to it. Why could it not be pretty much as he says? It seems to me that fueling this resistance is a nagging sense that access just has to be constitutive of conscious experience, that we just cannot understand what it would be to be conscious without it. But given the concession already made that some access is involved in phenomenal consciousness, why not go along with Block’s interpretation of the Sperling and other data? Why insist on report-access in particular? I cannot speak for Block’s opponents, but I suspect that reasoning along the following lines underlies a good part of the resistance to his position- First, there is the relatively conceptual point that consciousness is constitutively related to subjective access– my aforementioned point about experience being more than mere instantiation. Once the notion of the subject– the “for whom” it is like what it’s like– enters the picture, we then ask who or what this subject is. Well, the natural thought is that the subject is the person, and the person is the entity that both plays the highest executive role in deliberation and planning action, and reports to others (and to itself). Hence, the idea of a subjective access that is divorced from reporting mechanisms seems hard to swallow, as there doesn’t seem to be a suitable candidate for the subject whose access is involved in the bit of phenomenal consciousness at issue. If I am right about the source of the resistance, then I think there are two lines of reply. First, it might be that subjective experience does not entail the existence of a subject, at least not anything like what we normally take a subject to be. While what is consciously attended to might involve access by the sort of high-level executive we associate with the personal level, and wenaturally think of as the subject, the person, it seems plausible that there are centers of experience more loosely connected in the mind and that do not involve an entity we would call a fullf ledged subject. I take Block’s argument here to show that this is plausible, given the data so far. The argument can be contested, of course, but I wonder what, besides a commitment to the conceptual binding of experience to a substantial subject, motivates the search for these alternative– and to my earstrained, interpretations of the data. Finally, one might retain the idea of a substantial subject as a necessary component of experience, and even retain the idea that the subject is that which reports. As Block noted in discussing Dehaene and Naccache’s division of the global workspace into I2 and I3, the only dispute here is whether what’s phenomenally conscious has to be in I3. Block isn’t denying that it must at least be in I2. But if I2 is understood as that pool of information from which I3 draws, then what counts as the subject can be identified with the union of I2 and I3. The point is that whatever bottleneck exists due to the processing that gets an item from I2 into I3 shouldn’t be taken to restrict what we count as the full-fledged subject of experience. Of course it might have been that way, and in the end it is an empirical question, as Block insists. But why think, as so many who insist on the constitutive connection between consciousness and reportability seem to, that it just has to be that way? Phenomenality without access? doi: 10.1017/S0140525X07002968 William G. Lycan Department of Philosophy, University of North Carolina, Chapel Hill, NC 275993125. ujanel@email.unc.edu http://www.unc.edu/~ujanel Abstract: Block holds that there can be “phenomenology,” “awareness,” and even awareness of the phenomenology, without cognitive access by the subject. The subject may have an experience and be aware of the experience, yet neither notice it nor attend to it. How that is possible is far from clear. I invite Block to explain this very fine distinction. I firmly endorse the idea that qualitative character overflows cognitive accessibility, because I believe we are often in sensory states that present qualitative features of which we are unaware. But Block makes a stronger claim based on a finer distinction. That distinction is unclear to me, and I invite him to explain it. He holds that there can be “phenomenology” and “awareness” without cognitive access by the subject. First, I distinguish Block’s distinction from the more familiar one between unconscious and conscious detection of a sensory quality. As noted, we often sense color or shape or sound or another environmental feature without being at all aware of doing so. But such nonconscious detection does not count as phenomenal for Block, since (a) as he uses that term, “when one has a phenomenally conscious experience, one is in some way aware of having it” (sect. 6, para. 1), and (b) for a mental state to be phenomenal, in Block’s usual use of the term, there must be “something it is like” to be in it. Yet according to him, such Awareness (his capital “A”) does not require cognitive accessibility. Why not? At least in part, because a mental state that includes it need not be one that “the subject notices or attends to or perceives or thinks about” (sect. 6, para. 3). But awareness of any sort is intentional, especially when “of” is explicitly appended. If one is aware of having an experience, in particular, the experience is the intentional object of the awareness. And I assume, without fear of disagreement from Block or any of his readers, that intentionality is representation. Therefore, a phenomenally conscious experience in his sense is one that is represented by one of the subject’s own psychological states. In light of Block’s allegiance to “same order” accounts of Awareness (sect. 6), I do not say that the experience is represented by another of the subject’s states; Block’s view is that the experience “consists in part in an awareness of itself” (sect. 6, para. 2), perhaps as if it were a conjunction along the lines of “There is some cheese over there and it is this very experience that tells me so.” 515 BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh But that “same order”–ness does not per se distinguish Awareness from noticing or (minimally) attending. As Block says, the awareness of itself is (only) part of the experience. So far as has been shown, it is a separable part, as is the foregoing cheese sentence’s second conjunct: there is the first-order component of the experience and another part that represents the first-order component, as in Gennaro (1996). So how does that latter representational part differ from noticing or attending?1 The most obvious guess would be in terms of passive versus active introspection. “Higher order” theorist Armstrong (1981, p. 63) distinguishes between mere “reflex” introspective awareness and “scrutinizing” or actively exploratory introspection. The former is merely a “watching brief” and not really worth calling “introspection,” while the latter is “introspection proper.” Though Armstrong does not say so, I daresay this is a matter of a low and routine level of attention versus a high and active level of attention. But that cannot be what Block means either. If the reflexive part of the experience were a matter of passive, routine “watching” and/or peripheral, low-level attention, it would still be watching and attention, which are what he is denying.2 Of course there is representation in the brain that does not constitute either noticing or attending. But the awareness Block is talking about is person-level; it is the whole subject who is supposed to be aware of her/his own experience. What, then, is Awareness, and how does it differ from the various forms and degrees of cognitive accessibility? NOTES 1. Kriegel (2005) faults Gennaro for so treating the first-order component and the self-referential part as separate and distinct; he maintains that the self-representation is somehow more “intrinsic” to the original state itself. But this is obscure and not explained. 2. Nor does help come from Block’s (1995b) pneumatic drill example, designed to illustrate “phenomenal consciousness” absent “access-consciousness”: “You were aware of the [drill] noise all along, but only at noon …[do you become access-]consciously aware of it” (p. 234; italics in the original). I can parse that in any of three ways: (1) You were detecting the noise all along, but only at noon do you becomeaware ofthe noise; (2) you were dimly aware of the noise all along, but only at noon do you become focally aware of it; (3) you were aware of the noise all along, but only at noon do you become aware of that awareness itself. Each of those makes sense, but I am pretty sure that none of them is what Block intended. The measurement problem in consciousness research doi: 10.1017/S0140525X0700297X Rafael Malach Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel 76100. rafi.malach@weizmann.ac.il http://www.weizmann.ac.il/neurobiology/labs/malach Abstract: States of sensory absorption may offer a means to disentangle perception from report. Interestingly, such states lead to an antagonistic relationship between perceptual and cognitive-access networks, suggesting that perceptual awareness does not depend on a read-out by high order cognitive-access mechanisms. Rather, it may emerge internally, through a cooperative coding dynamics, whereby each neuron simultaneously represents and reads-out the perceptual awareness state. Block forcefully illustrates a challenging methodological difficulty inherent in consciousness research: the measurement problemthat is, the fact that any exploration of consciousness depends on some kind of report, either external or through introspection. Consequently, one is invariably faced with the difficult task of 516 disentangling the neuronal mechanisms associated with such reports from those underlying the phenomenal experience (e.g., sensory perception) itself. Human functional magnetic resonance imaging (fMRI), which can provide a highly detailed mapping of the conscious human brain, nevertheless suffers particularly severely from this methodological confound due to its sluggish temporal dynamics. Howthen can onedisentangle these closely related processes? Block provides an impressive survey of sophisticated experiments suggesting that reportability can be distinguished, and in fact is not necessary for phenomenal experience. Here I will present an alternative approach which nevertheless agrees with the notions proposed by Block– both point to the feasibility of phenomenal perception without a reporting perceiver. The idea is quite straightforward: If the reporting/introspection stage can somehow be sufficiently segregated in time from the perceptual stage, one may be able to study in isolation the brain areas engaged during perception without confounding them with those involved in reporting and introspection. In such an experimental paradigm, the report/introspection of the percept is obtained only at a later stage, through recollection. It could be argued that such a clean temporal separation of perception from reporting is simply not feasible. However, there are many instances in which it seems that perception occurs without any overt report or introspection. A striking example is the condition of sensory absorption, in which engagement with the perceptual stimuli is so intense that one gets the strong sense of “losing oneself in the act.” Another, more common type of experience may happen when watching a highly engaging movie– again, one is clearly not in the business of reporting or self-introspection during such states. Of course, there is no a priori reason to assume that such intuitive impressions of self-loss indeed reflect a true neuronal dissociation of perception from any self-related processes; for example, it could be that implicit activation of cognitive-access areas may occur even during highly absorbing moments. In particular, it has been suggested that neural processes underlying an implicit first-person perspective may be an essential element of any conscious awareness state. Here is where fMRI research may prove useful, because it allows the mapping of any neuronal activity, be it conscious as well as implicit or subconscious during such engaging moments. So what does brain imaging during absorbing perceptual moments reveal? In an fMRI study of brain activation in subjects watching a highly engaging movie (Hasson et al. 2004), the results revealed a robust and wide-spread activation in the back (i.e., sensory part) of the cerebral cortex, in a system of areas we termed the “Extrinsic” system (i.e., cortical regions oriented towards the external environment). In contrast, the front part of the brain remained relatively unresponsive. Indeed, even in the back part we found several relatively unresponsive islands. This entire set of nonresponsive areas constituted a coherent system (largely overlapping with the default mode network; Raichle et al. 2001)) which we termed the “Intrinsic” system because of its complementary nature to the sensory-driven Extrinsic system. We hypothesized that the intrinsic/extrinsic divide may reflect a fundamental functional organization of the human cortex (Golland et al. 2007). Our research, as well as that of many others, have indicated that the Intrinsic system deals with internally oriented functionsprecisely the network one would assume is the most likely candidate for mediating cognitive access, introspection, and reportability, as well as the “first person perspective” (Baars et al. 2003). Critically though, the Intrinsic network in fact shows a strong reduction in activity precisely during moments of intense perceptual processing (Goldberg et al. 2006; and see Fig. 1 further on here). Thus, not only do we fail to find fMRI evidence for a synergistic activation of sensory representations in the back of the brain with self-related networks in the front, BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh Figure 1 (Malach). Intrinsic and extrinsic systems. Antagonistic relationship between the extrinsic and intrinsic systems (light and dark patches, respectively) during an intense visual recognitions task. Arrows point to the high fMRI activation in the LOC region of the extrinsic system (right inset), as opposed to inhibition of activity in the SFG, a self-related part of the intrinsic system (left inset). Lateral view of an “inflated” left hemisphere. Back is to the right. [Modified from Goldberg et al. (2006) and Golland et al. (2007).] but intense sensory engagement actually appears to shut off these cognitive access networks! In summary, fMRI data during perceptual engagement suggests that perceptual awareness can emerge through internal activity in sensory systems, without a need to be “read out” by higher-order cognitive access mechanisms. Finally, on a cautionary note, it should be emphasized that the present conclusions should be tempered by the methodological limitations of fMRI. Hence, substantial neuronal activity may go undetected by the fMRI method if the neuronal representations are too small (Avidan et al. 2002), or the signals are too rapid to affect the sluggish hemodynamic fMRI response. Furthermore, cortical regions which do not modulate their activity levels during sensory perception may go undetected using our standard fMRI methodology. Ontheotherhand, it is tempting to consider the more speculative implication of these recent findings: the notion that phenomenal experience may emerge through internal processing within sensory representations proper has far reaching consequences for neuronal theories of consciousness. To see why, let us consider, f irst, the concept of population coding, which is a widely accepted notion of sensory representations. In such coding schemes, the combined pattern of activity in a group of neurons (the population vector or state) represents a sensory percept,say a yellow color (see Fig. 1) generated by virtue of the fact that a “green” and a “red” neurons (R and G in Fig. 2) are active while the “blue” neuron (B) is not. Importantly, in conventional models, this network state is then read out by a higher-order station. Such coding allows a huge combinatorial power (e.g., Levy et al. 2004). However, note that here we consider the possibility that phenomenal experience emerges within the bounds of the sensory representations themselves, without assuming a hierarchical flow into a high order read-out area. Instead, I would like to propose that the percept is coded cooperatively by the sensory network itself (see Fig. 2). Therefore, in such a scheme the phenomenal experience emerges when all relevant neurons in a network are informed about their own population state. Note that in such a cooperative coding model (somewhat Figure 2 (Malach). Two alternative schemes for perceptual representations. In conventional population coding (A) the neuronal state is read out by high-order areas. In the “cooperative coding” scheme there is no hierarchical processing. The neuronal state is both generated and read out by the same neurons through their lateral connectivity. Here I propose that the latter dynamics leads to phemonenal experience. analogous to a point attractor dynamics) there is no hierarchical processing– each active neuron simultaneously serves the roles of reading out and representing the perceptual state. Intriguingly, this single principle seems to successfully account for a large body of recent experimental data: for example, the high f iring rates, relatively long durations, and dense local connectivity which appear to be critical for the emergence of conscious perceptual states. To summarize, the field of consciousness research appears to be in the midst of an exciting period where the experimental jury is still out regarding such fundamental issues as the minimal spread of neuronal activity that is sufficient to elicit a conscious percept. However, in complete agreement with Block, I believe that these issues are experimentally tractable and will certainly lead to great advances in the construction of testable neuronal theories of conscious awareness. 517 BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh Dodging the explanatory gap– or bridging it doi: 10.1017/S0140525X07002981 Drew McDermott Computer Science Department, Yale University, New Haven, CT 06520-8285. drew.mcdermott@yale.edu http://www.cs.yale.edu/homes/dvm Abstract: Assumingourunderstanding of the brain continuesto advance, we will at some point have a computational theory of how access consciousness works. Block’s supposed additional kind of consciousness will not appear in this theory, and continued belief in it will be difficult to sustain. Appeals to “what it’s like” to experience such-and-such will carry little weight when we cannot locate a subject for whom it might be like something. Block says he wants to sidestep the “explanatory gap,” but I’m afraid that it is too wide to walk around– you have to find a way to get across it. Let us suppose we had acompletely worked-out explanation of how information flows between the various chunks of brain discussed in the target article. Let’s stipulate, with the author, that the explanations are roughly at the level of neural networks as described by Koch (2004). They will therefore be computational, in the sense that they would leave little room for distinctions between the actual brain and any device that passed equivalent coded messages between nodes standing for assemblies of neurons. It seems likely that we will possess such explanations in the foreseeable future. At that point we will know how “access” in the author’s sense will happen; that is, let us suppose, how information is distributed to a global workplace in Baars’ (1997) framework. Will we also know how “phenomenology” happens? (I mean “phenomenology” in the sense Block uses it in sentences such as, “Sperling’s clever idea was to test … whether the phenomenology persists after the stimulus was turned off by…”; target article, sect. 9, para. 2.) Well, no, we won’t. The computational explanation of how information flows in order to enable subjects to report a row of Sperling’s (1960) array after hearing a tone will of course not refer to anything like phenomenology, but only to neural structures playing the role of buffers and the like. This is what Chalmers (1996) calls the Paradox of Phenomenal Judgment, which is just another angle on the Explanatory Gap. Block would like it to be the case that phenomena play a role in our psychological abilities. To extract a few exemplary phrases from section 9: [S]ubjects are able to deploy working memory so as to access only half the rectangles despite the fact that …subjects’ reported phenomenology is of seeing all or almost all of the rectangles. …[Suppose] the subjects are continuing to maintain a visual representation of the whole array– as subjects say they are doing …(sect. 9, para. 6) and The subject has persisting experiences as of more specific shapes than can be brought under the concepts required to report or compare those specific shapes with others. (sect. 9, para. 10) Notice how terms like “working memory,” “phenomenology,” “visual representation,” “experiences,” and “concepts” are used as though they all belong at roughly the same level in the explanatory hierarchy; but, in fact, in our envisioned computational explanation the “phenomenology” and “experiences” will drop out, as they seemingly always do. Our intuition that experiences are somehow inspected in making phenomenal judgments is,1 as I argue at greater length in McDermott (2001), exactly backwards. The inspections are computational events that must precede the experiences, causally and temporally. If an experience is reported, or accessed in some weaker sense, then we can explain it by reference to how the 518 brain thinks about itself.2 But if an experience happens without being accessible, then it becomes a phantom. Let me draw an analogy here. If we continue to suppose that cognitive science finds a satisfying computational explanation of visual processing and access consciousness, the unaccessed experiences will be in a position analogous to unobserved electrons in a two-slit experiment demonstrating interference of their wave functions. Some physicists, such as David Bohm (Bohm & Hiley 1993), found it hard to believe that an electron could shed its particlehood for all except brief flashes of time, and devised theories in which electrons always remained particles, whose positions ingeniously served as indices to wave functions. Few in the mainstream physics community found this theory attractive, for some technical reasons, but also for an easily grasped one: The “positions” in Bohm’s theory, being in principle completely unobservable, were obviously vestigial ornamentation on a theory that was otherwise an inelegant variant of ordinary (nonrelatavistic) quantum mechanics. It seems clear that if we get a cognitive-scientific (i.e., a neuroscientific or a cognitive-psychological) explanation of access to experience, we are going to go through an intuition change at least as violent as that brought about by quantum physics. I think it is inevitable that our understanding of consciousness will change as radically as our understanding of, say, life, has since the seventeenth century. Will this be a new “definition” of consciousness? Block supposes (sect. 3) that we can always rephrase questions about phenomenology using the popular but at best vacuous formulation asking “what it is like” to have a particular experience. However, one has to ask to whom it might be “like something” for the fusiform face area of brainlesion patient G.K. to light up when it is not like anything to G.K. himself? I amactually in sympathy with the author’s stance on methodology. I think the Occamish arguments he uses to justify his conclusions can be valid. I just don’t think Block’s methodological razor is a match for the scientific buzz saw that is cutting through this area of science. NOTES 1. Note the unspoken premise in the quote from the target article above that the phenomenology of eight somethings must somehow be eight– what? Phenomenologies of some kind, I guess– only a few of which can be snatched before evanescing. 2. In other words, we can place it within the framework of a “higherorder thought” theory of phenomenal consciousness, although not the caricature of that hypothesis described by the target article in section 6; of course the theory does not posit that every conscious thought is conscious by virtue of another conscious thought targeted at it. If it did, the obvious infinite regress would make the theory unattractive to just about anyone aware of post-Renaissance developments in philosophy of mind. Reportability and illusions of phenomenality in the light of the global neuronal workspace model doi: 10.1017/S0140525X07002993 Lionel Naccachea,b and Stanislas Dehaeneb aFe´de´ration de Neurophysiologie Clinique, Fe´de´ration de Neurologie, Hoˆpital de la Pitie´-Salpeˆtriere, Paris, France; bINSERM Cognitive Neuro-Imaging Unit, CEA/SAC/DSV/DRM Neurospin Center, Gif/Yvette Cedex, France. lionel.naccache@normalesup.org dehaene@cea.fr Abstract: Can we ever experimentally disentangle phenomenal consciousness from the cognitive accessibility inherent to conscious reports? In this commentary, we suggest that (1) Block’s notion of phenomenal consciousness remains intractably entangled with the need BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh to obtain subjective reports about it; and (2) many experimental paradigms suggest that the intuitive notion of a rich but non-reportable phenomenal world is, to a large extent illusory– in a sense that requires clarification. In avery stimulating target article, Ned Block places phenomenal consciousness at the core of his conceptual framework for consciousness (Block 1995b; 2001; 2005). In the past, we have proposed that access of information to a prefronto-parietal global neuronal workspace, capable of broadcasting that information to many distant cortical areas and therefore making it available for verbal or nonverbal report, is the essential ingredient of a theory of conscious perception (Dehaene & Naccache 2001). For Block, however, conscious reports fail to capture the whole conscious experience (and this incompleteness is not imputable solely to spurious factors such as reporting biases or errors). Block defends the existence of a phenomenal consciousness irreducible to conscious reportability. The key problem that we have with his thesis is its lack of empirical testability. Can we ever experimentally disentangle phenomenal consciousness from the cognitive accessibility inherent to conscious reports? In this commentary, we suggest that (1) Block’s notion of phenomenal consciousness remains intractably entangled with the need to obtain subjective reports about it; and (2) many experimental paradigms suggest that the intuitive notion of a rich but non-reportable phenomenal world is, to a large extent illusory– in a sense that requires clarification. 1. Reports, conscious access, and phenomenology. If one wants to define phenomenal consciousness differently than conscious reportability, then one should resist the temptation to make use of subjects’ reports to credit the existence of phenomenal consciousness. If the only support for the existence of phenomenal consciousness comes from conscious reports, then we find no reason to accept a major distinction between these two concepts. Yet Block’s argument makes recurrent use of subjects’ reports to advocate the existence of phenomenal consciousness. For instance, Block states: When one has a phenomenally conscious experience, one is in some way aware of having it. (sect. 6, para. 1) In this case, aren’t we also able to report it? Later, when discussing Sperling’s seminal “iconic memory” experiments, Block writes: I am taking what subjects say at face value. (sect. 9, para. 6) and Howdoweknowwecanbelievesubjects’reports tothe effect that they experience all or almost all of the objects in the Sperling and the Landman et al. experiments? (sect. 9, para. 15) In these sentences, Block relies heavily on subjective reports. He suggests that they provide face-value support for a rich phenomenal experience, supposedly going way beyond the few details that can actually be reported. Yet this seems to prove our point: Availability for report remains the sole criterion for conscious perception. We are still waiting for a clear, empirically usable definition of “phenomenality” or “qualia” that goes beyond what can be done based on subjects’ reports alone. 2. What is a report? It is, however, essential to better define what we mean by “report.” A report is not a “cut and paste” copy of a visual scene, but rather a conscious comment on an inner mental representation. This representation can originate from perceptual systems at multiple levels, but ultimately it results from their redescription by evaluative and interpretative systems. At any given moment, it provides only a partial and possibly biased description of the perceptual scene. In our view, the fact that, on any given trial, subjects cannot report the whole scene is therefore non-essential– what is essential is that any consciously visible item is accessible for report. Block’s comments on split-brain patients, locked-in patients and aphasic patients, also prompt us to remind him that conscious reports can be nonverbal or even become entirely covert, due to motor system impairments (Gazzaniga et al. 1977; Laureys et al. 2005). The absence of overt verbal report in patients is not diagnostic of the absence of conscious access and of internal form of “self-report” (e.g., internal speech). Using neurophysiological tools such as functional magnetic resonance imaging (fMRI) and event-related potentials (ERPs), indirect conscious reports can be obtained from these patients. They can and should be further complemented by looking for other psychological properties which are thought to be exclusive to conscious processing, such as active maintenance of mental representations (Owen et al. 2006) or dynamic regulation of executive control. In this broader definition, the reportability criterion is far from being a “behavioristic ladder” (see target article, sect. 4, para. 5)– rather, it provides an excellent test of whether or not an information is conscious accessible (Naccache 2006b). 3. Sperling’s experiments. Block interprets Sperling’s iconic memory experiments (Sperling 1960) and their recent extension by Landman et al. (2003) as a clear proof of a rich though non-reportable phenomenal world. We disagree, and propose an alternative interpretation of these experiments in the global neuronal workspace framework. What happens in the brain when a large array of letters is briefly flashed, then removed? Since no mask is present, there is no reason to doubt the subject’s report that he or she is aware of the array. The conscious content presumably stems from both a dorsal map of approximate letter locations (perhaps in area lateral intraparietal [LIP]) and a ventral representation of the letters (perhaps in area V4; Dehaene et al. 2004). Both dorsal and ventral representations must be jointly accessed by prefrontal regions when subjects report that they see a spatially extended array of letters. Sperling’s experiments clearly demonstrate that all individual letters remain represented for ~1 second within a posterior, presumably retinotopic location-specific buffer (iconic memory). However, other studies indicate that when attention is distributed, temporal and prefrontal regions act as capacity-limited f ilters and cannot represent more than a few objects (Kastner et al. 1998). When subjects report seeing “all the letters,” we suggest that they distribute their attention globally over the array, and thus are only able to determine its approximate numerosity and “letterhood”; our model predicts that only this approximate content, not the detailed letter identities, accesses a fronto-parietal global neuronal workspace. When subjects report individual letters, they change to a focused attention mode that allows them to enhance one location at a time, to let its specific content access the global workspace, and, therefore, to name it. Our model predicts that in this case, a local subregion of letter-sensitive retinotopic cortex (e.g., V4) becomes temporarily synchronized with anterior cortices and transmits a reportable visual content to prefrontal cortex (for related evidence, see Haynes et al. 2005; Sergent 2005). The model we just sketched, although in need of further specification, seems capable of accounting for the subjects’ reports within the global neuronal workspace without appealing to Block’s hypothesis of non-reportable phenomenal states. The mismatch between the report of seeing the whole array and the reduced capacity to report the individual letters therefore fails to provide univocal support in favor of Block’s phenomenalitywithout-report hypothesis (as noted above, it does not even speak to this issue, since it is a mismatch between two reports). 4. Theillusion of seeing. Part of the confusion surrounding the Sperling paradigm may stem fromourdescription of the report of seeing the whole array as an “illusion of seeing” (Dehaene et al. 2006). The term “illusion” applies imperfectly to Sperling’s paradigm because, after all, the subjects’ introspection turns out to be veridical: they can see the whole array, and they can, when probed, report any of its letters (though not all of them at once). However, the term “illusion” emphasizes that, until information is accessed by the fronto-parietal workspace, it is 519 BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh illusory to think that subjects necessarily have veridical knowledge of it. Indeed, our model predicts that, if a single letter of the Sperling array was replaced by another letter or even a digit prior to the focused attention stage, subjects might not notice it and still maintain that they “see all the letters”– a clear illusion. This substitution paradigm would lead to many testable predictions. For instance, a subpart of area V4 should have veridical information about the symbol’s identity, which could be decoded by fMRI (see Haynes & Rees 2006; Williams et al. 2007)– but this spot should be (temporarily) functionally disconnected from frontal decision areas, and its information should not be used in subject’s reports. Many other paradigms and neuropsychological syndromes (Naccache 2006a) that are not discussed by Block indicate that reports of a rich phenomenality cannot be taken at face value (though we agree with Block that they still have to be explained in all of their details). In the “moving window” paradigm, for instance, where a computerized display is changed in synchrony with eye movements,viewers claim that they see a normal page of text even when all parafoveal information is replaced by strings of X’s (Rayner & Bertera 1979). Similarly, we all have the illusion of seeing a world in full color although color-sensitive cones are absent in the periphery of our retina. Such illusions suggest to us that building a theory of consciousness based on intuitions of phenomenality without reportability may be building on sand. Phenomenal consciousness lite: No thanks! doi: 10.1017/S0140525X07003007 J. Kevin O’Regana and Erik Myinb aLaboratoire Psychologie de la Perception, CNRS– Universite´ Paris Descartes, Centre Biome´dical des Saints Peres, 75270 Paris cedex 06, France; bCentre for Philosophical Psychology, Department of Philosophy, Universiteit Antwerpen, 2000 Antwerpen, Belgium. jkevin.oregan@gmail.com Erik.Myin@ua.ac.be http://nivea.psycho.univ-paris5.fr http://www.ua.ac.be/erik.myin Abstract: The target article appeals to recent empirical data to support the idea that there is more to phenomenality than is available to access consciousness. However, this claim is based on an unwarranted assumption, namely, that some kind of cortical processing must be phenomenal. The article also considerably weakens Block’s original distinction between a truly nonfunctional phenomenal consciousness and a functional access consciousness. The new form of phenomenal consciousness seems to be a poor-man’s cognitive access. A central piece of the argument presented in the target article is Ned Block’s claim that “phenomenal consciousness overflows cognitive accessibility” (target article Abstract). Block’s main motivation for this claim is his intuition, shared by most of us, that we see muchmorethanwecanreport.Thefeelingisparticularly clear when an image is flashed before us, and we feel we have seen “everything in it,” yet generally will be unable to report more than 3 to 5 elements from the scene (the classic Sperling “whole report” paradigm). Thetrouble isthat anexplanation for this feeling of being able to see morethanwereportmightlieinthefactthattheearlystagesof the visual system possess a certain degree of neural persistence. This neural persistence or “icon” might not itself be phenomenally conscious. Instead, it might, for a short while, be available for access by higher cortical mechanisms. Our impression of seeing “everything” might therefore derive not from actual phenomenality of the icon, but from the immediate availability for access of information in this persistent subcortical icon. This is where Block musters new evidence from the recent experiments of Landman et al. (2003) and Sligte et al (2008). These experiments, contrary to the original Sperling experiments 520 (Sperling 1960), show that the neural persistence that seems to be involved in giving us the impression of seeing everything can sometimes be of considerably longer duration than previously measured. Information about the orientation of eight rectangles, for example, can sometimes be recovered as long as one second after stimulus extinction. This long persistence suggests that the information cannot be subcortical but must be of cortical origin, and Block concludes that for this reason it is likely to be phenomenal. So Block’s argument contains this critical step: the step consisting in assuming that if something provides an impression of detail, and its substrate is cortical, then it is likely to be phenomenal. This makessensetoBlockbecausehestartsfromanaprioriassumption that consciousness is a “natural kind” and has some kind of “neural signature.” Converging evidence, he says, suggests that if certain neural conditions are met (e.g., being cortical rather than subcortical), then visual information in the brain becomes conscious. However, the neural signature hypothesis is merely speculative. It could indeed turn out that there is neural commonality in every case of consciousness, but why should one start out with this assumption? Moreover, even if it were the case that an identifiable neural signature for consciousness existed, what would its significance be? Block himself suggests it would leave us still struggling with a “hard problem” of consciousness, showing that this neural signature would give us little insight into phenomenal consciousness. Leaving aside the criticism of Block’s use of recent empirical data in defense of his hypothesis, we are surprised at another aspect of his argument. Block once had a program of disproving philosophical functionalism. There were two kinds of consciousness: phenomenal consciousness and access consciousness. Phenomenal consciousness was pure and nonfunctional. Block thought the existence of phenomenal consciousness (for which he adduced empirical and theoretical material) proved there was more to consciousness than the functional (Block 1995b). The problem, critics quickly pointed out, was that something purely nonfunctional, something that has no effects, and in principle can have no effects, is not only undiscoverable (any observation would be an effect), but epiphenomenal as well: it cannot even have any effects on the phenomenology of the subject in whose consciousness it is present. Nevertheless, if the goal of showing the plausibility of a nonfunctional phenomenal consciousness were attainable, this would be an important result. But in the target article the opposition between the realm of the phenomenal and the realm of access is diluted. Today’s version of phenomenal consciousness is no longer completely access-resistant. After all, Block musters evidence for its existence by noting that people report that they think they have seen everything in the scene even though they cannot always report all the details. So this is a report, just not a full report. Furthermore he claims further evidence by saying that they can report the details if cued early enough. This is also a report! Thus, instead of the original strong opposition between functional access consciousness and nonfunctional phenomenal consciousness, there now seems actually to be a tight link between this new (avowedly less-than-) cognitive access, and phenomenal consciousness. Indeed, nothing in the present target article indicates phenomenal consciousness cannot be interpreted as a weaker variant of access consciousness. Importantly, and further encouraging this interpretation, phenomenal consciousness also no longer gets identified with the qualitative, often called “what-it-is-like” aspects of consciousness. If phenomenal consciousness is no longer sharply distinguished from access consciousness, a significant issue on the Scientific Explanation of Consciousness is transformed into a rather minor quibble about the scope of the access subjects have to visual information in psychological experiments! Deciding whether subjects can describe four or eight masked items after a certain number of milliseconds is perhaps an important BEHAVIORAL AND BRAIN SCIENCES (2007) 30:5/6Commentary/Block: Consciousness, accessibility, and the mesh project in psychology and neuroscience, but resolving the question does not seem like a big advance on the mind/body problem.