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Consciousness, accessibility, and the mesh between psychology and neuroscience Ned Block Department of Philosophy, New York University, New York, NY 10003 ned.block@nyu.edu Abstract: Howcanwedisentangle the neural basis of phenomenal consciousness from theneural machinery of the cognitive access that underlies reports of phenomenal consciousness? We see the problem in stark form if we ask how we…

You may have heard of a famous paper by George Miller called ‘The Magical Number Seven, Plus or Minus Two: Some Limits on Our Capacity for Processing Information’ (Miller 1956). Although Miller was more circumspect, this paper has been widely cited as a ©2008 The Aristotelian Society Proceedings of the Aristotelian Society, Vol. cviii, Part…

Phenomenal and Access Consciousness Ned Block and Cynthia MacDonald CONSCIOUSNESS AND COGNITIVE ACCESS NED BLOCK This article concerns the interplay between two issues that involve both philosophy and neuroscience: whether the content of phenomenal consciousness is ‘rich’ or ‘sparse’, whether phenomenal consciousness goes beyond cognitive access, and how it would be possible for there to…

Consciousness-of It is very often (but not always—Dretske, 1993) assumed that a conscious state is a state that one is conscious of being in (Lycan, 1996a). I am willing to agree in order to focus on other matters. The HOT theory has an attractive explanation of this claim, because consciousness-of can be cashed out as being the object of a HOT. However, there are two other accounts of why a conscious state is one that one is conscious of being in, and these accounts are preferable to the HOT account—according to the viewpoint of the biological theory and the global workspace theory. The deflationary account (Sosa, 2003) says that all there is to being conscious of one’s experience is the triviality that in having an experience, one experiences it, just as one smiles one’s smile and dances one’s dance. Consciousness-of in this sense is to be firmly distinguished from attending to one’s experience (Burge, 2006). One can have a conscious experience of red, and that experience can have whatever awareness comes with conscious experience, even in the absence of top-down attention to it (Koch & Tsuchiya, 2007). Another rival to the higher order account of why a conscious state is one that one is conscious of is the same order account in which block: comparing the major theories of consciousness  Gazzaniga_77_Ch77.indd 1115 1115 6/19/2009 10:08:00 AMa conscious pain is reflexive in that it is about itself. That is, it has a content that turns back on itself, and that is what makes a pain a state one is conscious of. This view had its beginnings in Aristotle (Caston, 2002) and was later pursued by Brentano (1874/1973). (See Burge, 2006; Kriegel & Williford, 2006.) Either one of the deflationary or same order accounts can be adopted by advocates of the biological view and the global workspace view, so I see no real advantage for the HOT view here. Further problems for the HOT theory I argued that the HOT theory cannot recognize an explanatory gap, but my argument was oversimple because it neglected a crucial distinction between two types of HOT theories. The kind of HOT theory that cannot recognize an explanatory gap is the ambitious HOT theory of phenomenal consciousness that analyzes phenomenal consciousness in terms of higher order thought. But there is also a modest and therefore innocuous form of the HOT theory that just says that, in addition to phenomenal consciousness, there is another kind of consciousness, higher order consciousness. Phenomenal consciousness is one thing, and higher order consciousness is another. The modest form can recognize an explanatory gap for phenomenal consciousness. The modest account is suggested by Lycan’s remark, “I cannot myself hear a natural sense of the phrase ‘conscious state’ other than as meaning ‘state one is conscious of being in’ ” (Lycan, 1996b). As Lycan recognizes, what one can and cannot “hear” leaves the theoretical options open. The modest account is tantamount to a verbal claim—that there is a sense of the term “conscious” (distinct from “phenomenal consciousness”) that has a higher order meaning—and does not dictate that there is no explanatory gap. The very short argument against the HOT theory (that it does not recognize an explanatory gap and so is false) is an argument only against the ambitious form of the HOT theory. In the rest of this section, I will explain some other problems with the ambitious HOT theory that also do not apply to the modest version. The first thing to realize about the HOT theory in both the ambitious and modest forms is that it needs considerable qualification. Suppose I consciously infer that I am angry from my angry behavior, or—in a slightly different kind of case that need not involve conscious inference—I am aware of my anger in noticing my angry fantasies. In these cases we would not say the anger is thereby conscious. Further, Freudians sometimes suppose that a subject can unconsciously recognize his own desire to, for example, kill his father and marry his mother, along with the need to cloak that desire in a form that will not cause damage to the self. But we would not say that in virtue of such an unconscious HOT (one that cannot readily become conscious) about it, the desire is therefore conscious! These examples concerning 1116  consciousness what we would say suggest that a HOT about a state is not something we regard as sufficient for the state to be conscious. Defenders of the HOT theory introduce complications in the HOT theory to try to avoid these counterexamples. Rosenthal (2005a) says that S is a conscious state if and only if S is accompanied by a thought to the effect that the subject is in S that is arrived at without inference or observation of which the subject is conscious. The italicized phrase avoids the problems posed by conscious observation of angry fantasies and conscious inference by stipulating that HOTs arrived at by conscious observation and inference are not sufficient for consciousness. (Another stipulation that I will not describe is supposed to handle the Freudian issue.) Suppose as a result of biofeedback training I come to have noninferential nonobservational knowledge of states of my liver (Block, 1995). Since we would not count the state of the liver as conscious in virtue of the HOT about it, Rosenthal (2000b, p. 240) further stipulates that only mental states can be conscious. What if I have a HOT about my future or past mental state? Rosenthal (2000b, p. 241) further stipulates that if one has a thought about a state, that makes it conscious only when one thinks of it as present to oneself. As Bertrand Russell noted in an often-quoted passage (1919, p. 71), “The method of ‘postulating’ what we want has many advantages; they are the same as the advantages of theft over honest toil.” Honest toil is not required if the HOT view is understood as a modest account, since stipulation is not a problem in a stipulated sense of a term, but ad hoc stipulation is a problem if we take the HOT view as an ambitious account, especially as an empirical theory of consciousness. A second class of issues concerns the “mismatch problem,” the possibility of a mismatch in content between a sensory representation and the accompanying HOT. What phenomenally conscious quality does an experience have if a HOT to the effect that one has a dull throbbing pain in the toe is accompanied not by any representation of toe damage but instead a visual representation of red—or by no sensory representation at all? If the sensory representation determines the conscious quality all by itself, the contents of HOTs are irrelevant here, and if here, why not elsewhere? And if the HOT determines the conscious quality without the sensory representation, then the contents of sensory representations are irrelevant—so what is the difference between thinking you have a delightful experience and actually having one (Byrne, 1997; Neander, 1998; Balog, 2000; Rey, 2000; Levine, 2001)? Of course, new sophistication in one’s HOTs, as when one learns to recognize different wines, can cause a corresponding differentiation in the sensory states that the HOTs are about, but HOTs are not always causally self-fulfilling (if only!), and in any case, causal self-fulfillment does not answer the constitutive question of what the difference is between thinking you have an experi6/19/2009 10:08:00 AM Gazzaniga_77_Ch77.indd…

Comparing the Major Theories  of Consciousness ned block abstract This article compares the three frameworks for theories of consciousness that are taken most seriously by neuroscientists: the view that consciousness is a biological state of the brain, the global workspace perspective, and an account in terms of higher order states. The comparison features the “explanatory gap” (Nagel, 1974; Levine, 1983), the fact that we have no idea why the neural basis of an experience is the neural basis of that experience rather than another experience or no experience at all. It is argued that the biological framework handles the explanatory gap better than do the global workspace or higher order views. The article does not discuss quantum theories or “panpsychist” accounts according to which consciousness is a feature of the smallest particles of inorganic matter (Chalmers, 1996; Rosenberg, 2004). Nor does it discuss the “representationist” proposals (Tye, 2000; Byrne, 2001a) that are popular among philosophers but not neuroscientists. Three theories of consciousness Higher Order The higher order approach says that an experience is phenomenally conscious only in virtue of another state that is about the experience (Armstrong, 1978; Lycan, 1996a; Byrne, 1997; Carruthers, 2000; Byrne, 2001b; Rosenthal, 2005a). This perspective comes in many varieties, depending on, among other things, whether the monitoring state is a thought or a perception. The version to be discussed here says that the higher order state is a thought (“higher order thought” is abbreviated as HOT) and that a conscious experience of red consists in a representation of red in the visual system accompanied by a thought in the same subject to the effect that the subject is having the experience of red. Global Workspace The global workspace account of consciousness was first suggested by Bernard Baars (1988) and has been developed in a more neural direction by Stanislas Dehaene, Jean-Pierre Changeux, and their colleagues (Dehaene, Changeux, Nacchache, Sackur, & Sergent, 2006). The account presupposes a neural network approach in which there is competition among neural coalitions involving both frontal and sensory areas (Koch, 2004), the winning coalitions being conscious. Sensory ned block New York University, New York, New York stimulation causes activations in sensory areas in the back of the head that compete with each other to form dominant coalitions (indicated by dark elements in the outer rings in f igure 77.1). Some of these dominant coalitions trigger central reverberations through long-range connections to frontal cortex, setting up activations that help to maintain both the central and peripheral activations. The idea that some brain areas control activations and reactivations in other areas is now ubiquitous in neuroscience (Damasio & Meyer, 2008), and a related idea is widely accepted: that one instance of reciprocal control is one in which workspace networks in frontal areas control activations in sensory and spatial areas (Curtis & D’Esposito, 2003). It is useful in thinking about the account to distinguish between suppliers and consumers of representations. Perceptual systems supply representations that are consumed by mechanisms of reporting, reasoning, evaluating, deciding, and remembering, which themselves produce representations that are further consumed by the same set of mechanisms. Once perceptual information is “globally broadcast” in frontal cortex this way, it is available to all cognitive mechanisms without further processing. Phenomenal consciousness is global broadcasting. Although the global workspace account is motivated and described in part in neural terms, the substantive claims of the model abstract away from neuronal details. Nothing in the model requires the electrochemical nature of actual neural signals. The architectural aspects of the model can just as easily be realized in silicon-based computers as in protoplasm. In this respect, the global workspace theory of consciousness is a form of what philosophers call functionalism (Block, 1980), according to which consciousness is characterized by an abstract structure that does not include the messy details of neuroscience. Another functionalist theory of consciousness is the integrated information theory (Tononi & Edelman, 1998), according to which the level of consciousness of a system at a time is a matter of how many possible states it has at that time and how tightly integrated its states are. This theory has a number of useful features—for example, retrodicting that there would be a loss of consciousness in a seizure in which the number of possible states drops precipitously block: comparing the major theories of consciousness  Gazzaniga_77_Ch77.indd 1111 1111 6/19/2009 10:07:59 AMFigure 77.1 Schematic diagram of the global workspace. Sensory activations in the back of the brain are symbolized by dots and lines in the outside rings. Dominant sensory neural coalitions (dark lines and dots) compete with one another to trigger reverberatory activity in the global workspace (located in frontal areas) in the center of the diagram. The reverberatory activity in turn maintains the peripheral excitation until a new dominant coalition wins out. (Tononi & Koch, 2008). Unfortunately, such predictions would equally follow from an integrated information theory of intelligence (in the sense of the capacity for thought, as in the Turing test of intelligence)—which also drops in a seizure. Consciousness and intelligence are on the face of it very different things. We all understand science fiction stories in which intelligent machines lack some or all forms of consciousness. And on the face of it, mice or even lower animals might have phenomenal consciousness without much intelligence. The separation of consciousness and cognition has been crucial to the success of the scientific study of consciousness. In a series of papers that established the modern study of consciousness, Crick and Koch (1990, 1998) noted in particular that the basic processes of visual consciousness could be found in nonprimate mammals and were likely to be independent of language and cognition. Although its failure to distinguish consciousness and intelligence is crippling for the current prospects of the integrated information theory as a stand-alone theory of consciousness, I will mention it at the end of the article in a different role: as an adjunct to a biological theory. The Biological Theory The third of the major theories is the biological theory, the theory that consciousness is some sort of biological state of the brain. It derives from Democritus (Kirk, Raven, & Schofield, 1983) and Hobbes (1989), but was put in modern form in the 1950s by Place (1956), Smart (1959), and Feigl (1958). (See also Block, 1978; Crane, 2000; Lamme, 2003.) I will explain it using as an example the identification of the visual experience of (a kind of) motion in terms of a brain state that includes activations of a certain sort of area MT+ in the visual cortex. Although this explanation is useful as an example, we can expect that any theory of visual experience will be superseded. 1112  consciousness Visual area MT+ reacts to motion in the world, different cells reacting to different directions. Damage to MT+ can cause loss of the capacity to experience this kind of motion; MT+ is activated by the motion aftereffect; transcranial magnetic stimulation of MT+ disrupts these afterimages and also can cause motion “phosphenes” (Zihl, von Cramon, & Mai, 1983; Britten, Shadlen, Newsome, & Movshon, 1992; Heeger, Boynton, Demb, Seideman, & Newsome, 1999; Kammer, 1999; Cowey & Walsh, 2000; Kourtzi & Kanwisher, 2000; Huk, Ress, & Heeger, 2001; Rees, Kreiman, & Koch, 2002; Théoret, Kobayashi, Ganis, Di Capua, & Pascual-Leone, 2002). However, it is important to distinguish between two kinds of MT+ activations, which I will call nonrepresentational activations and representational activations. Some activations in the visual system are very weak, do not “prime” other judgments (that is, do not facilitate judgments about related stimuli), and do not yield above-chance performance on forced-choice identification or detection (that is, they do not allow subjects to perform above chance on a choice of what the stimulus was or even whether there was a stimulus or not). On a very liberal use of the term “representation” in which any neural activation that correlates with an external property is a representation of it (Gallistel, 1998), one might nonetheless call such activations of MT+ representations, but it will be useful to be less liberal here, describing the weak activations just mentioned as nonrepresentational. (The term “representation” is very vague and can be made precise in different equally good ways.) However, if activations of MT+ are strong enough to be harnessed in subjects’ choices (at a minimum in priming), then we have genuine representations. (See Siegel, 2008, for a discussion of the representational contents of perceptual states.) Further, there is reason to think that representations in MT+ that also generate feedback loops to lower areas are at least potentially conscious representational contents (Pascual-Leone & Walsh, 2001; Silvanto, Cowey, Lavie, & Walsh, 2005). (For a dissident anti-feedback-loop perspective, see Macknik & Martinez-Conde, 2007.) Of course, an activated MT+ even with feedback to lower visual areas is not all by itself sufficient for phenomenal consciousness. No one thinks that a section of visual cortex in a bottle would be conscious (Kanwisher, 2001). What makes such a representational content phenomenally conscious? One suggestion is that active connections between cortical activations and the top of the brain stem constitute what Alkire, Haier, and Fallon (2000) call a “thalamic switch.” There are two important sources of evidence for this view. One is that the common feature of many if not all anesthetics appears to be that they disable these connections (Alkire & Miller, 2005). Another is that the transition from the vegetative state to the minimally conscious state (Laureys, 2005) involves these connections. However, there 6/19/2009 10:07:59 AM Gazzaniga_77_Ch77.indd 1112is some evidence that the “thalamic switch” is an on switch rather than an off switch (Alkire & Miller, 2005) and that corticothalamic connections are disabled as a result of the large overall decrease in cortical metabolism (Velly et al., 2007; Alkire, 2008; Tononi & Koch, 2008)—which itself may be caused in part by the deactivation of other subcortical structures (Schneider & Kochs, 2007). Although this area of study is in flux, the important philosophical point is the three-way distinction between (1) a nonrepresentational activation of MT+, (2) an activation of MT+ that is a genuine visual representation of motion, and (3) an activation of MT+ that is a key part of a phenomenally conscious representation of motion. The same distinctions can be seen in terms of the global workspace theory as the distinction among (1) a minimal sensory activation (the gray peripheral activations in figure 77.1), (2) a peripheral dominant coalition (the black peripheral activations in figure 77.1), and (3) a global activation involving both peripheral and central activation (the circled activations in figure 77.1 that connect to the central workspace). The higher order account is focused on the distinction between a visual representation and a conscious visual representation (2 versus 3), a visual representation that is accompanied by a higher order thought to the effect that the subject has it. Here are some items of comparison between the three theories. According to the biological account, global broadcasting and higher order thought are what consciousness does rather than what consciousness is. That is, one function of consciousness on the biological view is to promote global broadcasting, and global broadcasting in some but not all cases can lead to higher order thought. Further, according to the biological view, both the global workspace and higherorder thought views leave out too many details of the actual working of the brain to be adequate theories of consciousness. Information in the brain is coded electrically, then transformed to a chemical code, then back to an electrical code, and it would be foolish to assume that this transformation from one form to another is irrelevant to the physical basis of consciousness. From the point of view of the biological and global workspace views, the higher-order-thought view sees consciousness as more intellectual than it is, but from the point of view of higher-order-thought accounts, the biological and global workspace accounts underestimate the role of cognition in consciousness. The global workspace and higherorder-thought accounts are sometimes viewed as superior to the biological account in that the biological account allows for the possibility that a subject could have a phenomenally conscious state that the subject does not know about (Block, 2007a, 2007b). And this is connected to the charge that the biological account—as compared with the other accounts—neglects the connection between phenomenal consciousness and the self (Church, 1995; Harman, 1995; Kitcher, 1995). The higher order and global workspace accounts link consciousness to the ability to report it more tightly than does the biological view. On the higher-order-thought view, reporting is just expressing the higher order thought that makes the state conscious, so the underlying basis of the ability to report comes with consciousness itself. On the global workspace account, what makes a representational content conscious is that it is in the workspace, and that just is what underlies reporting. On the biological account, by comparison, the biological machinery of consciousness has no necessary relation to the biological machinery underlying reporting, and hence there is a real empirical difference among the views that each side seems to think favors its own view (Block, 2007b; Naccache & Dehaene, 2007; Prinz, 2007; Sergent & Rees, 2007). To evaluate and further compare the theories, it will be useful to appeal to a prominent feature of consciousness, the explanatory gap. The explanatory gap Phenomenal consciousness is “what it is like” to have an experience (Nagel, 1974). Any discussion of the physical basis of phenomenal consciousness (henceforth just consciousness) has to acknowledge the “explanatory gap” (Nagel, 1974; Levine, 1983): nothing that we now know, indeed nothing that we have been able to hypothesize or even fantasize, gives us an understanding of why the neural basis of the experience of green that I now have when I look at my screen saver is the neural basis of that experience as opposed to another experience or no experience at all. Nagel puts the point in terms of the distinction between subjectivity and objectivity: the experience of green is a subjective state, but brain states are objective, and we do not understand how a subjective state could be an objective state or even how a subjective state could be based in an objective state. The problem of closing the explanatory gap (the “Hard Problem” as Chalmers, 1996, calls it) has four important aspects: (1) we do not see a hint of a solution; (2) we have no good argument that there is no solution that another kind of being could grasp or that we may be able to grasp at a later date (but see McGinn, 1991); so (3) the explanatory gap is not intrinsic to consciousness; and (4) most importantly for current purposes, recognizing the first three points requires no special theory of consciousness. All scientifically oriented accounts should agree that consciousness is in some sense based in the brain; once this fact is accepted, the problem arises of why the brain basis of this experience is the basis of this one rather than another one or none, and it becomes obvious that nothing now known gives a hint of an explanation. block: comparing the major theories of consciousness  Gazzaniga_77_Ch77.indd 1113 1113 6/19/2009…

That was the spatial point. The temporal point is that attentional resources available to the supposed spotlight are to some extent shared among other aspects of perception, for example, other modalities, and with executive control mechanisms (Brand-D’Abrescia & Lavie, 2008) and cognition. Nilli Lavie and her colleagues have demonstrated many kinds of cases in which…

The Effect is Perceptual Although there has been some controversy over what exactly these results show (Anton-Erxleben, Abrams, & Carrasco, 2010; Carrasco, Fuller, & Ling, 2008; Prinzmetal, Long, & Leonhardt, 2008; Schneider, 2006; Schneider & Komlos, 2008), it has been settled beyond any reasonable doubt that the effect is a genuine perceptual effect rather than…

Non-selective Attention 1 There are many convincing examples of attention changing appearance in a way that does not involve selecting some properties and de-selecting others. The effect I will be appealing to requires a small amount of practice in moving one’s attention without changing fixation, but once one manages this it is a strong effect.…

ATTENTION AND MENTAL PAINT1 Ned Block New York University Abstract Much of recent philosophy of perception is oriented towards accounting for the phenomenal character of perception—what it is like to perceive—in a non-mentalistic way—that is, without appealing to mental objects or mental qualities. In opposition to such views, I claim that the phenomenal character of…

Indeed, Rosenthal thinks that we have evidence of such a determination of what it is like by a HOT independently from any first order state, in a ‘change blindness’ experiment by James Grimes (1996). As Rosenthal (2009a: 162) puts it: ‘In one case of change blindness, a large parrot switches back and forth between being…