The principle that guides this essay is that the study of consciousness requires a multidisciplinary approach because consciousness is, in all probability, a multifactorial phenomenon. However, once this honeymoon period of disciplines is over, each discipline will need to generate relevance if we are to continue exploring the same target. The word consciousness is used with a variety of connotations and it means something different to many. However, once agreed on the use of one connotation, the explorative research should adhere to this, if not universal, at least operational connotation. The exhaustive analysis of this phenomenon might force us to rethink the definition. This would be a healthy outcome. However, a clear identification of the target is still necessary in the beginning. Many publications deal with related but not relevant «consciousness» terms and this is dangerous because it is adding related but irrelevant information that is counterproductive to the study of «consciousness».
A classic illustration is the paper published by PSYCHE: «The Decoupling of «Explicit» and «Implicit» Processing in Neuropsychological Disorders. Insights Into the Neural Basis of Consciousness?» by Faulkner and Foster (2001). This is an informative summary of explicit and explicit cognitive processes but its impact on the consciousness debate is minimal at best and very likely to be counterproductive because of its philosophically ill informed background. The merit of this paper is simple; it is a good catalogue of neuropsychological syndromes that involve neglect. It clearly shows that there is a discrepancy between what «neglect» patients report and their true preserved, albeit implicit, information in the impaired domain; this discrepancy applies to a series of neuropsychological disorders. A brief summary of this paper is pertinent here.
In neuropsychology, «neglect» refers to disorders characterised by a lack of awareness of (usually) half of the presented information. For example, patients suffering «unilateral neglect» show impaired processing of information presented on the side that is contralateral to the location of the brain insult. Studies however, suggest that some processing, occurring on the presumably neglected area does take place implicitly. Therefore, the patient is not overtly aware of this. The evidence presented by the authors comes from studies investigating blindsight, amnesia, object agnosia, prosopagnosia, hemi-neglect, and aphasia. Their analysis, they claim, will have repercussions on « a) possible clinical therapies in brain-injured patients as well as b) the architecture of cognition and c) the neural basis of consciousness in non brain-damaged individuals» (p.1). A crucial distinction offered by the authors is about their understanding of «consciousness». They state that, although they acknowledge existing distinctions of the word consciousness, they prefer to refer in their paper, to «explicit knowledge» as relating to those aspects of cognition which the individual has access to. Conversely, implicit processing refers to cognitive processes, which the individual does not have access to. Thus, explicit memory for example can be tested by asking the individual to report on the content of a specific memory, whereas implicit memory can be detected by behavioural changes due to the influence of previously «unaware» acquired information. I will briefly explain the phenomenon of blindsight to illustrate the authors' strategy.
Blindsight occurs when a brain insult causes a loss of vision, as reported by the patient, but there is preserved implicit processing based on information presented in the «blind» area. There is ample experimental evidence demonstrating that patients alter their behaviour in tasks influenced by implicitly gained information. This adjustment of behaviour is beyond what chance could bring about and it appears to be directly influenced by the relevant stimulus, with the patient remaining unaware. An important figure in the introduction of this concept is Weiskrantz and colleagues (1974) who described a case study in which the patient developed left hemianopia (blindness in the left visual field of both eyes) after surgical removal of a significant portion of the striate cortex in the right hemisphere. After the patient was asked to visually discriminate between stimuli presented in the blind field, the patient would report that he could not do so. However, when asked to guess, the answer he gave would be strikingly accurate. He was asked to point the location of stimuli, orientation of different lines (vertical versus horizontal), and shapes (cross versus circle). Other studies have found other types of visual discrimination equally accurate in hemianopia patients; for example, reaching and grasping, discerning meaning of words, varied shapes and so on (in Faulkner and Foster 2002).
These findings are analogous to those found in memory research whereby a brain insult can damage the ability to recall new information (anterograde amnesia) and the ability to recall information prior to the insult (retrograde amnesia). There appears to be ample evidence suggesting the existence of preserved implicit memory. A traditional experimental method uses amnesic and normal subjects who would be presented with word stems for example and be required to complete the stem with the first word that comes to mind. Both controls and amnesic subjects were more likely to complete the stems with words from a list that had been previously studied of which amnesic subjects had not explicit recollection. In an experiment of this nature, the priming effect consists in the fact that amnesic subjects, although scoring poorly on a simple recall test (explicit mode), still showed an influential effect (implicit mode). Similar findings are reported from the visual agnosia area. In visual agnosia patients fail to identify familiar objects by sight even though there is no physical damage to the visual apparatus. However, they can identify objects if presented in a different sensory modality (e.g., touch, hearing). The same phenomenon has been established in Prosopagnosia (impairment of facial recognition) whereby patients have reported an inability to recognise familiar faces. However, they have significantly different (larger) skin conductance responses as compared to their reaction when exposed to unfamiliar faces. In the language domain, aphasic patients (expressive and/or receptive language impairment) have also demonstrated preserved implicit language comprehension and expression in spite of impairment. Further examples of implicit processing come from the neglect area, which is an attentional deficit of (generally) left visuo-spatial stimuli, normally as a consequence of right hemisphere damage. This hemineglect has been observed in behaviours such as dressing only the right part of the body, eating the food from the right side on the plate only, omitting words placed in the left visual field when requested to read a paragraph and so on. However, preserved processing on the neglected space has been reported. This has been usually investigated using preferential choices in the absence of explicit recognition of the stimulus presented in the neglected space. That is, on subsequent stimuli presentations (hemineglect) subjects would still choose a stimuli (e.g., an intact house) as opposed to a less preferred option (e.g., a house with the left part of it in flames) even when the portion representing adverse stimuli was in the neglected field.
Faulkner and Foster's paper was published in Psyche, (a very eclectic and multidisciplinary journal) which deals with the mystery of consciousness and its various contributors are supposed to approach the topic in a pluralistic fashion. However, it appears they are making the topic flexible enough to suit every single connotation of the word consciousness -- Faulkner and Foster's paper is an example. The discussion on consciousness is plagued with these sorts of nominal accidents. One wonders if the question asked in the title (unanswered in the paper) refers to the type of question with which this journal is concerned. The authors of the paper deliberately equated consciousness with «awareness». From that moment on, everything is permitted and the relevance to the consciousness domain is avoided. Terms such as explicit, implicit, unawareness, (Freudian)unconsciousness, covert/overt, belong to a family of concepts that denote primarily cognitive «awareness». As briefly described above, all the neuropsychological disorders mentioned are analysed in the light of awareness or accessibility from the patient's point of view. This awareness represents a challenge of its own accord but it is not necessarily equated with the subjective experience of phenomenal character and the potential link between awareness and consciousness (phenomenal experience) is not even mentioned. The literature on awareness is vast and cognitive psychology has embarked on a prolific study. For the last 20 years it has covered varied areas such as implicit memory, with Graf and Schafter, (1985) being some of the pioneers in revitalising interest; skill acquisition processes (controlled) leading to «automatic» (that is, lacking awareness) processes, work which started importantly with Schneider and Schiffrin (1977); and the learning domain which was pioneered by Reber (1967). The terminology used in these areas moves freely between, «implicit learning», «unconscious learning», and «unaware learning». The same applies to memory, and skill acquisition. These are just some of the domains cognitive psychology has ventured into exploring the notion in which the subject reports being «aware» (of something recalled, learnt, or practiced).Foot note 1_1
More contemporary work in this area has developed and applied to abnormal manifestations of information processing. For example MacLeod's workFoot note 1_2 has focused on implicit selective information processing of depressive and anxious patients, and drawing from earlier work by Beck (1967) has extensively investigated the idiosyncratic selective cognition of this population. MacLeod focuses on the cognitive biases of individuals suffering from affective disorders and suggests that these cognitive processes are outside the realm of the individual's awareness. Thus, the thought content that this population engage in is systematically distorted by cognitive biases that take place «automatically», and outside the realm of unawareness. Perhaps the best known proposal about the unconscious is that offered by the psychoanalytical tradition initiated by Freud and his invention of the concept of «unconscious». Given that it is a particularly familiar proposal I will therefore not examine it here. Suffice to say that the characteristic feature of Freud's unconscious is exactly the contention that is a whole set of memories, desires, fixations, etc. that are not accessible to the individual, that is, that the individual is not aware of them (e.g., a childhood experience/trauma).
Faulkner and Foster's review of implicit processes in neuropsychological disorders resonates entirely with the domain investigated in fields like learning, memory, skills acquisition, emotional pathology, and the Freudian tradition. However, these areas do not necessarily refer to consciousness, that is subjective experiences, or phenomenal experience, (qualia) or other more precise descriptors that have been used to refer to consciousness. Their work fit nicely within the psychological tradition, which explains behaviour but does not examine «consciousness». It does, fit, as put by Chalmers (1996), within the characteristic concern of psychology, that is, mind as the internal basis of behaviour. It follows the tradition of explaining «how» a mental process causes behaviour, not «what» a mental state «feels like». I have purposefully used the word awareness when describing the content of their paper but the authors used interchangeably «unconscious», «unaware», and «implicit» terms. This reflects the lack of familiarity with the philosophical inquiries into consciousness, which is not a feature restricted to Faulkner and Foster. But one wonders if by publishing in a journal like Psyche this confusion might not be perpetuated. One wonders also if mistakes they generate such as the use of expressions like «conscious awareness» (used by others too) are innocent tautologies (in that they incessantly used consciousness as a synonym of awareness) or whether it reflects a deeper confusion.
A similar criticism can be applied to Schiff and Plum's attempt to shed light on normal consciousness (Schiff and Plum, 2000). An underlying assumption of their article is that the understanding of the pathology of human consciousness is a first step in understanding mechanisms underlying human consciousness. The paper aims to «(1) explore the neurology of impaired consciousness and detail a brief taxonomy of global disorders of consciousness, (2) place these neurological diseases in the context of the underlying anatomy and physiology of arousal and `gating' systems, (3) examine the role of the gating systems in fluctuations of cognitive function and recovery from states of impaired consciousness, and (4) consider the possible contributions of these clinically-rooted approaches to further understanding of human consciousness» (p.1). The authors' expectations are clear; understanding what human consciousness is via studying disorders of human consciousness is a promising project. The definition of consciousness used by Schiff and Plum is in a way more confusing than that used by Faulkner and Foster in that from the outset, this paper appears to center on wakefulness more than anything else. They offer, as their basic definition of consciousness, the one given by James (1894 in Schiff and Plum, 2000), which appears to draw attention to «awareness» (of the individual and his/her environment).
The detailed neurological account offered by the authors is beyond the scope of this essay. Of considerable however interest is their understanding of consciousness. What follows is a brief description of the first part of their essay, which is of more interest to this paper in that it specifies the «type» of consciousness to which they refer. The taxonomy favoured by the authors involves a classification of global disorders of consciousness that include: stupor and coma, the vegetative state, akinetic mutism, absence and partial complex seizures, delirium, dementia and hyperkinetic mutism.
Coma is an unarousable state characterised by unresponsiveness to internal or external stimuli and a loss of all neuropsychological aspects of normal functioning. In its observable behaviour, it resembles a deep, sleep-like unconsciousness. Coma contrasts with stupor in that stupor refers to impairment of arousal but some responses (although inconsistent) to the environment can still be detected in stupor. The persistent vegetative state (PVS) differs from coma in that in PVS cyclic arousal recovers but there is still no evidence that the patient is aware of his/her environment. The overall cerebral metabolism in PVS, as revealed by positron emission tomography (PET), is reduced by 50% (similar to those patients undergoing deep surgical anesthesia). Some behavioural and physiological «activity» has been reported in PVS patients. For example, one patient of one of the article's co-authors expressed occasional single (understandable) words. The patient's PET investigation revealed isolated activity of the left cerebral structure, which was operating at a very low metabolic rate. However, it was still prominently activated as compared to the rest of the patient's brain. Another disorder included in their analysis is akinetic mutism, which refers to a state in which patients appear vigilant and attentive but remain motionless and have a profound impairment of neuropsychological functioning. Neuropathological analysis reveals the involvement of the frontal lobes, either directly or indirectly. An opposite condition is hyperkinetic mutism characterised by unrestrained but coordinated motor activity with no apparent awareness of self or environment. This rare condition appears to involve bilateral destruction of temporal parietal occipital junctions and wider lesions compromising occipital-parietal regions. The authors also postulate seizure disorders as part of consciousness disorders. In both absence seizures and complex seizures, patients develop momentary vegetative-like states with attentional and intentional failures and loss of working memory and intra-ictal perceptual dissociation. Other less pervasive conditions (in that some functioning is preserved) are Delirium and Dementia. Schiff and Plum state that delirium's main characteristic is a temporal disorientation whereas dementia's main feature is at first a gradually increasing memory dysfunction reaching a stage which might be difficult to differentiate from a vegetative state. The term `consciousness' used in their paper is clearly related to a family of terms, which resonate with «sustained wakefulness», «awakening», «arousability» and so on. The fact that we are «awake» is uninteresting and interesting at the same time. It is intellectually interesting in the sense that to reach a level of knowledge that allows us to know the neurological substrates implicated in arousability and eventually in sustained wakefulness will solve one of the mysteries haunting the study of biological entities. This knowledge is fascinating; much needed and will, in all likelihood, have consequences in many other areas of the functioning of the human brain. However, it is uninteresting when one wants to examine a particular aspect of the human mind, that is, consciousness, and to focus on its basic nature. The state of being awake is shared with many other species and appears to be related to consciousness in that «most» consciousness appears to take place when one is awake (though this is highly debatable as well, for example, in pain sensations while one is asleep). But they are still two different phenomena. Breathing, for example, is in a sense even more necessary for consciousness for if we were not breathing consciousness would not be possible. However to include studies on breathing (a function which is also shared with all other living species) in a debate about «consciousness» would appear intuitively overinclusive and intellectually interesting but strictly speaking irrelevant.
Because the word consciousness can be used to describe wakefulness as well as a phenomenal experience, it does not seem to be powerful enough to be included in the same debate (or it shouldn't anyway). To do this, creates the sense that we are getting closer when in fact it is adding unnecessary distractions. The study on wakefulness (as the study on breathing) does not appear to shed much light on the subjective phenomenal experience, which one would think, is the main target interest for the «consciousness community». And if it does, the link is consistently missing. Different neurological disorders include different levels of cyclical arousal and different levels of awareness of the self and the environment. For example, coma epitomises unresponsiveness to the environment whereas PVS appears more complex in that some responsiveness has been reported. Similarly, absence seizures involve a momentary loss of attentional and mnestic faculties. All these disorders create a massive dissociation within the individual and with his/her environment, momentarily or permanently, which makes the researcher's access to the patient's neuropsychological functioning impossible. Therefore, we can only assume, and rightly so in all probability, that their cognitive abilities are impaired. Needless to say, their subjective experience of colour or pain, etc. is equally inaccessible and the researcher assumes therefore equally impaired. Is this assumption warranted? Is it the same in Delirium as in PVS or coma? Do we have enough information for this conclusion? The authors conduct neuropathological analyses via neuroimaging techniques, which reveal the organic lesion site or low metabolic activity, thus giving a good account of the putative neurological substrates subserving wakefulness, and there is where they have to stop. It appears as if the study of consciousness as such (as in the philosophical interest) requires a different level of analysis.
This present paper does not favour discarding studies of implicit/explicit processes or the neurology of impaired wakefulness. On the contrary the examination of these domains would greatly enhance the study of consciousness. However, first we need to agree on what we are studying. For example if we decide that consciousness refers to a subjective experience which is characterised by intentionality and volition (this is an example only) then a re-examination of implicit /explicit processing in the light of volition and/or intentionality would generate interesting and relevant information. The same analysis can be re-considered with neurological disorders affecting these constituent aspects of consciousness. For example, are there neurological disorders that affect intentionality or volition? Perhaps some do and some do not. Here the taxonomy proposed by Schiff and Plum would need to be readjusted according to which aspect of consciousness is being employed.
The entanglement into which philosophy has driven itself when exploring consciousness has been unnecessarily complicated by lack of agreement on terminology. It would be pretentious and ambitious, for example, to re-baptise Freudian unconscious as a theory of awareness (the implicit). However, something like this is needed. There is a clear distinction between the Freudian unconscious and the state of being awake.
Phenomenal consciousness, access consciousness, content of consciousness, double consciousness, consciousness proper, real consciousness, transitive consciousness, intransitive consciousness, self-consciousness, creature consciousness, core consciousness, peripheral consciousness, primary consciousness, secondary consciousness; Please! To understand and follow the technical study of these various aspects of consciousness has become an exercise on its own. Do these «different types of consciousness» allude to different ontological entities? Are they overlapping, partly overlapping, or the same? What a mess. Paraphrasing Searle's observations regarding the criticisms of his basic philosophical «default» positions, it is as if in order to keep business running, some philosophers have created an artificial language which eventually becomes an independent subject of study with little to do with «consciousness». These terms seem to have departed from the notion of consciousness so violently that there seems to be something called consciousness and something totally different from «the study of consciousness». A preliminary step to any analytical definition is to establish identity criteria and this is the step that is missing and keeps messing up the landscape so badly. Consciousness is intrinsically complex and does not need extra, unnecessary, yet avoidable complications.
There seems to be a general agreement on the fact that there is such a mess in the literature. Many authors acknowledge this in their introductory paragraphs as they proceed to explain their own theories on consciousness. However, no serious attempts are made to solve this and we end up with yet more «surnames» for consciousness. A notable paper on this is that of Block (1995) who carefully points out the existence of this nominal problem. I have chosen to present a brief summary of Block's paper here as it illustrates the main propositions of the present essay. However, Block's solution tends to obscure the discussion rather than solving it. His criticism of the «messy» state of affairs in the study of consciousness is sharp and precise, but when attempting to solve it, he generates a new nomenclature, namely phenomenal consciousness and access consciousness. I will use his proposition to illustrate the fact that he could have used the word «awareness» to distinguish access to information, instead of piling more names on already cluttered consciousness terminology. The tenet of Block's proposition is that there are different notions of consciousness and this has led to numerous confusions about its analysis. He uses the phenomenon Blindsight to illustrate the existence of a fallacy that characterises this field. Blindsight has led many authors to postulate that one of the functions of consciousness is to harness or to enable information represented in the brain to guide action. This fallacy, Block claims, is revealed when one uses a more pertinent distinction in the consciousness area, that is, Phenomenal consciousness (P-C) and Access consciousness (A-C).
Block's argument uses Schacter's model to suggest that P- consciousness is
Using the phenomenon Blindsight (see previous section), Block postulates that a module specialising in visuo-spatial information has information about verticality of stimulus. A lesion has damaged a pathway between this specialized module and the phenomenal conscious system creating the «blind spot». The consequence is that the patient has no phenomenally consciousness experience of the line. And hence his executive system has no information about the whether the line is horizontal or vertical. The specialized module has a direct connection to the response system therefore when the subject is given a forced binary choice, the specialized module can somehow directly affect the response. It has been postulated that if the subject is given longer exposure (studies using alexics) their guesses are inaccurate. The explanation would be that the executive system takes over, and it prevents the peripheral system from controlling the response.
Many theories dealing with consciousness fail to address the question about P consciousness. For example, Crick and Koch (1990 in Block, 1995) claim to explain the mystery of C but their physiological examinations and propositions probably deal with the binding problem more than P consciousness (35-75 Hertz hypothesis). Many language/thought cognitive and neuropsychological experiments are addressing cognitive phenomena with no theoretical perspective of what P consciousness is. This is a powerful insight on Block's part and the basic argument of his observation of conflations. Block argues for example that Baars's theory «global worspace» is presented as a theory of P-consciousness but it is clearly a theory of A-consciousness. The same thing applies to Mandler's theory. Similarly, Schallice states that his theory of consciousness is about P-C, but it is an information processing theory of A-C. Edelman's proposition is about A-C and self-consciousness not P-C. Kosslyn and Koening's theory suffers the same problem, although it claims to be a theory of P-C, their theory is about A-C and monitoring consciousness. Kihlstrom postulates that the phenomena of implicit perception are about P-C. However, they claim that self-consciousness is what is lacking in implicit perception. They state that events come into consciousness when there is contact between the representation of the event (fact node) and the representation of oneself (self node). Blocks counterargument is that there are creatures (e.g., babies or other species) that have P-consciousness but have no «self-node». Andrade identifies C with the «executive systems» (systems that coordinate lower-level information processing). Here again they are conflating P and A-C. Jacoby and colleagues, examine experiences in which there is perception without «subjective experience» (subliminal perception). Therefore, their work focuses on A-C but they assimilate P and A-C. Schacter postulates that his work focuses on P-C but he frequently reverts to A-C when examining neuropsychological defects (e.g., anosognosia). Dennett postulates that consciousness is a cultural construction. For Block, A-C is as close as we get to the official view of Dennett's C, but closer comparisons are difficult as Dennett's view is that C is not a real ontologically independent phenomenon. Searle normally uses the notion of degrees of consciousness, but when he does so he ends up admitting somewhat Block's distinction of P and A-C.
There are quite a few observations about Block's strategy, but to review them here would be beyond the scope of this essay. They are well examined by several commentators in the replies to his target article. A salient criticism is his lack of evidence when hypothesising the existence of Access Consciousness (see for example Baars, 1995). My main observation, as I wish to stick to the nominal arena, is that there is nothing stopping Block from using «awareness» instead of «access consciousness». Why use «consciousness» to signify something different? There is something, a phenomenon, or set of phenomena that is encapsulated by the word «awareness». There is nothing controversial about this; however, the controversy arises when one is invited to accept not only his highlighting of the confusion but also the interaction between his putative P and A-C. The relationship of awareness and consciousness is another matter and it deserves much examination. However, since we know that they refer to something different let us start by using different terms to distinguish them. Block's initial concern about the conflation of P and A-C is unreservedly supported in this essay. The problem comes with his alternative proposition. To attribute some sort of consciousness to blindsighters is potentially confusing, as attributing some sort of consciousness to zombies would be equally misleading.
Chalmers's approach when defining consciousness appears to be less contaminated (1996). He speaks of the error of identifying the psychological with the phenomenal. He acknowledges the confusing state of affairs regarding its definition but favours remaining closer to the phenomenal aspect of consciousness. His characterization of consciousness involves the essential subjective experience, and he uses a set of terms that resonate with consciousness which include: experience, qualia, phenomenology, phenomenal, subjective experience, «what is like». The analytical approach to consciousness, and the other family of terms, will not be embarked upon here.
With this background in mind, one could use the terminology presented thus far and build a clear distinction of family of terms:
|Subjective experience Automatic|
|«What is it like»|
Notice that this classification responds to a necessity to «identify» phenomena in the consciousness area. The «analysis» of these phenomena is something different and was not attempted in this essay. How does wakefulness relate to consciousness? How do implicit information processes relate to consciousness? and so on, are meritorious analyses and needed for further clarification. However, to use these families as one entity is to start off on the wrong foot, and a considerable source of confusion. This sort of distinction would allow to clearly conceptualise issues such as the fact one can be not awake and have consciousness (e.g., sensation of pain while sleeping), one can be awake and process information and not aware, therefore devoid of the experience (e.g., blindsight), and so on.
Where does this come from? At a content level analysis this is not a confusion, it is a deliberate attempt to, on one hand accept the existence of consciousness as experience (thus rejecting accusations of radical eliminitivism) while keeping the methods and ideas within the known framework of empirical science (Varela, 1995). This comfort zone makes cognitive scientists reluctant to value and explore areas more difficult to operationalise (e.g., memory versus the feeling of red). Some blame Descartes and perhaps rightly so. Behaviourism is another offender. If Behaviourism admitted to any mental life, it was deemed irrelevant in understanding behaviour. The less dogmatic behaviorists referred to mind exclusively in psychological processes; they would not even contemplate the phenomenal aspect of mind. In addition, the advent of cognitive science and their entire focus on the psychological aspect of mind as ultimately responsible for behaviour is probably a significant influence in this prevailing attitude. At a more generalized level, and perhaps significantly more influential because of this, the common use of the word consciousness (with its numerous derivative connotations) has been unduly reproduced in the expert literature by some philosophers. For example, a very basic common dictionary (there are a few) would give two definitions: 1) being conscious: We have no consciousness during sleep. The blow caused him to lose consciousness. He did not recover/regain consciousness until two hours after the accident. 2) all the ideas, thoughts, feelings, wishes, intentions, recollections, of a person or persons: the moral consciousness of a political party. Definition one refers to the state of being awake and the second to consciousness as an umbrella term, which contains lots of «mental» activities such as memory, thoughts and feelings. In a better dictionary (e.g., Oxford) the word consciousness contains eight entries. A few are obsolete, or no longer in use, and date as far back as 1639 (it is paradoxical that after three and a half centuries we are still unsure about its definition). This dictionary also refers to consciousness in two basic dimensions; one denotative of wakefulness and another denotative of «mental activity». One could hardly blame an unspecialised dictionary for not disambiguating between subjective experience and awareness (or grouping every mental activity under one word).
Unfortunately, in many cases the expert literature has inherited this ambiguity, making progress a little slower than it should. For example, John Searle's (1990) definition of consciousness:
Notice that Searle includes wakefulness, subjective states and awareness in the definition of consciousness. Issues arising from this definition will necessarily be misleading in that some will focus on awareness or wakefulness when trying to establish the nature of consciousness (e.g., Faulkner and Foster, 2001; Schiff and Plum 2000, respectively). Or simply, they will advance the psychological aspect of the awareness tradition. In this respect the paper by Faulkner and Foster for example appears to be a nice continuation of an already established tradition in the implicit processing of emotional pathology (e.g., MacLeod, 1991) applied to the neuropsychological domain. However, nothing is said about the impact of this not-so new field on «consciousness». I am fully aware of Searle's defense of the irreducibility of consciousness, but his overinclusive definition does, perhaps tacitly, justify an unrestricted invitation to cognitive scientists to «explore» consciousness. The problem with this open invitation is that the subjective experience tends to remain unexamined.
In summary, common dictionary definitions of consciousness are extremely ambiguous and this has been carried through to more specialized definitions (e.g., Searle). These types of definitions are overinclusive and refer to at least three different types of phenomena. Solving this type of mistake would lead to content progress not just nominal clarifications. For example, studies of neuropathology affecting consciousness would be different to studies of neuropathology studying wakefulness. Similarly, studies connecting neuropsychological neglect and awareness would look different to studies linking neuropsychological neglect and consciousness. Perhaps based on this distinction, refocusing on alternative methodologies with a phenomenological orientation is warranted, (e.g., Neurophenomenology, Varela, 1995; the three principles proposed by Chalmers, 1996, i.e., coherence, organizational invariance and the double aspect theory of information). However, because there are fundamental differences between Varela and Chalmers, analysis of these differences would deviate us from the less controversial nominal issues. Thus, identifying what we mean by consciousness is a first step even when we want to deny its existence (e.g., Dennett, 1990). Furthermore, it appears clumsy to acknowledge the ambiguity and at the same time introduce more confusion by not differentiating enough among different types of phenomena or differentiating it by introducing more descriptors of consciousness (e.g., Block, 1995). The link between consciousness and some other mental activity (e.g., awareness, memory, executive functioning, etc.) is a logical next step and there is abundant literature doing this, but not all of them differentiate among associated yet different phenomena.
[Foot Note 1_1]
A good review is provided by Kirsner et al (Eds., 1998) in their «Implicit and Explicit Mental Processes». Another interesting recent review is «Out of mind. Varieties of unconscious processes» (Gelder, De Haan and Heywood, 2001).
[Foot Note 1_2]
MacLeod, 1992; MacLeod, Mathews and Tata, 1986; MacLeod and Rutherford, 1992, MacLeod and Hagan, 1992, MacLeod and Mathews 1991; MacLeod and McLaughlin, 1994; MacLeod and Lawrence Cohen, 1993 and MacLeod, Rutherford, Campbell, Ebsworthy and Holker, 2002.