What is Consciousness?
Review of The Science Of Consciousness by Max Velmans (Ed.)
Patrice Terrier
Laboratoire Travail et Cognition
UMR CNRS 5551, Universite Toulouse II
5 allees A. Machado
F-31058 Toulouse Cedex 1
FRANCE
terrier@univ-tlse2.fr
Copyright (c) Patrice Terrier 1999
PSYCHE, 5(19), July 1999
Previously held: http://psyche.cs.monash.edu.au/v5/psyche-5-19-terrier.html
KEYWORDS: consciousness, psychology, neuroscience, cognitive science.
REVIEW OF: Max Velmans (Ed.) (1996). The Science of Consciousness: Psychological, Neuropsychological and Clinical Reviews. Routledge.
xii + 207pp. ISBN 0-4151-1082-3. Price: $US23; pbk.
Max Velmans is very clear about what a scientific understanding of
consciousness must be:
Thus, to understand what consciousness is, we need to understand
what causes it, what its function(s) may be, how it relates to
nonconscious processing in the brain and so on (p. 3).
After pointing to structural features of this new book (section 1) I try
to highlight its contribution to the different questions raised by this
quotation (sections 2, 3, 4) and then signal some difficulties I had
when reading the book and questions I have after reading it (section 5).
In the final section (section 6) I give a snapshot of the book.
1. Structural Features
This book is organised into nine chapters in the following order: An introduction to the science of consciousness (Velmans); Perception without awareness of what is perceived, learning without awareness of what is learned (Kihlstrom); On consciousness in relation to memory and learning (Gardiner); Cognitive views of consciousness. What are the facts? How can we explain them? (Baars & McGovern); Neural processes in the production of conscious experience (Libet); Dissociable aspects of conscious experience (Young); Somatic consequences of consciousness (Sheikh, Kunzerdorf & Sheikh); The placebo effect (Wall); What and where are conscious experiences? (Velmans).
The chapters consist of original papers, including psychological,
neuropsychological and clinical reviews. Although the clarity of the
book is worthy of note, the integration of clinical reviews is a further
distinctive feature. For example, a major reference book for cognitive
psychologists interested in consciousness, Varieties of Memory and
Consciousness (Roediger & Craik, 1989) integrated cognitive,
neurocognitive and developmental reviews; no clinical reviews were
included. Does this feature reflect the possible use of new methods or
theories concerning consciousness? Although the clinical reviews
included provide interesting material by showing mind-body interactions
(sections by Sheikh et al. and Wall), by highlighting the need for and
practical consequences of a better understanting of the
consciousness-brain relationship, this integration reflects more a
change in the sense of the word 'consciousness' than the possible use of
new methods and models.
Indeed, the word 'conscious' can be used to mean different things: intentionality of retrieval, focal-attentive processing, monitoring, self-consciousness, and so on. In this book, the great majority of papers reflect the sense 'awareness' rather than 'intentionality of retrieval' (Roediger & Craik, 1989) >> see note 1 <<
2. What (and Where) Consciousness Is
In the final chapter Velmans states that classical dualists and
reductionists disagree about what consciousness is, but generally agree
where it is (somewhere in the brain), in so far as it can be located at
all. The reflexive model is then introduced (Velmans, 1990) in order to
suggest that experiences are where we experience them to be, a position
which is distinct from both dualism (experiences have no location in
space) and reductionism (experiences are in the brain). As Velmans
argues (chapters 1 and 9), definitions need not be final for research to
begin. It is enough that definitions be sufficiently similar for
different investigators to be able to agree that they are investigating
the same thing. For Velmans, consciousness means awareness (sometimes
phenomenological consciousness). Although most of the chapters seem
consistently to be dealing with the same meaning of consciousness
(awareness), investigators differ somewhat with respect to what
consciousness is.
For some contributors (Velmans, Gardiner, Baars & McGovern, Kihlstrom,
Wall), consciousness is the product - or the by-product - of information
processing. In this case, the question of the location of consciousness
is not of primary interest. Typically, Baars and McGovern consider, on
the basis of the Global Workspace theory (Baars, 1988) that
consciousness is a distributed property in the brain.
On the other hand, for those who discuss consciousness as a function of
brain activity (Libet, Young) the question arises as to where
consciousness is. A comparison of the two chapters by Libet and Young
shows that there is no necessary relationship between arguing that
consciousness is the product of brain activity and searching for the
location of consciousness in the brain; a point too often neglected in
my opinion.
Libet discusses the role neural processes have in the production of
conscious experience. Again, consciousness is treated as awareness:
"only introspective report by the subject can have primary validity as
an operational measure of a subjective experience" (p. 47). However, the
focus of his review is on the usefulness of PET and MRI technologies for
measuring consciousness and in the neural conditions which are adequate
to support conscious experience. Positron emission tomography (PET) and
magnetic resonance imaging (MRI) allow one to study changes in uptake
and turnover of metabolic and pharmacological agents. Libet convincingly
argues that these tools can, at best, tell us where in the brain
activities have changed. Neither the identification of neuronal activity
patterns that may be uniquely involved, nor the causal relationship
between brain activity and conscious experience, can be examined with
PET or MRI. Electrophysiological techniques are then reviewed. In order
to identify specific kinds of neuronal activities that elicit a
conscious experience, Libet seems to favour event-related potentials
(ERPs) recorded in response to a sensory signal, which "do provide some
direct correlates of conscious experience" (p. 102). Why is Libet so
interested in ERP techniques? On the basis of his own research, Libet
explains that the early components of ERPs represent neural responses
that are a direct function of the stimulus parameters. They vary with
changes in stimulus intensity, repetition, area, etc. The latter
components of ERPs (beginning at 150ms after the signal) vary
considerably with cognitive processes (e.g., subjects' attention) but
the specific essential components have not been identified.
Young also considers consciousness to be the product of brain activity.
However his emphasis is on the indirect nature of this relationship.
This section differs from Libet's chapter in at least two ways. First,
there are different forms of consciousness: among other distinctions,
phenomenal consciousness vs. access consciousness, direct experience vs.
reflexive consciousness. Young points to these different forms of
consciousness in order to suggest that there are different aspects to
consciousness which will need to be accounted for in different ways.
Consciousness is not a unitary phenomenon. Second, and perhaps more
important, consciousness cannot be caused by any neuronal activity:
Wakefulness and arousal are influenced by the brain reticular formation,
and especially noradrenergic neurons and the locus coerulus...Such
facts make it abundantly clear that consciousness is a product of brain
activity. However, we also know that consciousness is not a direct
result of any neuronal activity, because there are plenty of things the
neurons in our central nervous systems do of which we are not aware,
like adjusting the size of the eye's pupil (p. 119).
Young develops the idea that consciousness is not a direct result of any
neuronal activity. Three arguments towards this assertion are given. (1)
Even for the cerebral cortex, neuronal activity is not in itself
sufficient to produce consciousness. (2) The transition from
consciousness is, in neural terms, more than simply a change from
neuronal inactivity to neuronal activity. It is as much a change in what
the neurons are doing. Here, Young explains that studies of the brain's
electrical activity indicate that when we are in deep sleep, cortical
neurons still do something, but that 'something' is different from what
they do when we are awake. (3) One can find changes that selectively
affect different aspects of consciousness. For example, Young refers to
severe impairment of access consciousness in amnesiacs whose phenomenal
consciousness is less impaired as revealed by indirect tests of memory.
Also, impairments of consciousness can be restricted to certain types of
content (movement, colour, face recognition, etc.). His review focusses
on developing this third argument and describing its implications.
For authors who discuss the idea that consciousness is the product of
brain activity, we have just seen that there is no necessity to locate
consciousness in the brain. Also we considered the answers they provide
to our second question: what causes consciousness? Cognitive accounts of
consciousness will now be discussed.
3. What Causes Consciousness?
Of primary interest here are the chapters by authors who consider
consciousness a product of information processing. These chapters
indicate to the reader major problems for cognitive psychologists. These
problems can sometimes be found in reviews of attention, working memory
and automaticity, and are related to the question "what causes
consciousness?". For example, Baars and McGovern indicate that recent
important cognitive theories simply solve this question as it has
generally been solved for years in the cognitive literature: by
appealing to an executive system which processes output from specialized
modules, without spelling out in detail the abilities of the executive
system or buffer. This type of difficulty is noticed by Baars and
McGovern when they examine recent cognitive theories dealing with
consciousness.
In order to understand what causes consciousness, one may use the
experimental method to contrasting conscious and unconscious processes
across numerous experimental domains. The cases of information
processing without consciousness which authors have chosen to discuss
are often based on the implicit memory and implicit learning literature.
Even if this literature does support the suggestion that consciousness
follows information processing rather than entering into it (Velmans,
1991), one may feel that the definition of the mechanism by which
information processing produces consciousness has not been sufficiently
developed.
Gardiner examines the direction in which research on implicit memory and
learning tasks seems to be heading. This chapter gives a clear picture
of the interests and limits of two methods that have been proposed in
order to deal with subject's state of awareness in putative tests of
implicit memory: the retrieval intentionality criterion (Schacter,
Bowers & Booker, 1989; see note <1>) and the process dissociation
procedure (Jacoby, 1991). These methods, falling into the category of
third-person accounts of consciousness, are criticized, and experiential
measures of consciousness are proposed in order to supplement
third-person accounts.
Kihlstrom's paper provides a contrast with Gardiner's emphasis on
experiential criteria. Kihlstrom contends that "...the evidence
favouring unconscious procedural learning is not as compelling as
evidence that the subjects' performance is mediated by consciously
accessible declarative knowledge structures" (p. 38). In implicit
learning studies, subjects can perform quite well in several
experimental situations in which the complex rules used were unknown or
even unpredictable, without being able to communicate verbally the
knowledge gained. This result was initially thought to reflect the
superiority of an unconscious learning process in comparison to a
conscious one when the situation is complex. But this conclusion
resulted from a weakness in the first person method used (often a
questionnaire). Indeed, subjects were simply asked the wrong questions
about their knowledge: if subjects in implicit learning experiments on
artificial grammar learning do not have conscious access to the complex
finite-state grammar, they do have conscious access to a portion of the
knowledge gained, and this partial knowledge is enough to explain their
performance (Dienes, Broadbent & Berry, 1991; Dulany, Carlson & Dewey,
1984, 1985; Matthews et al., 1989; Perruchet & Pacteau, 1990, 1991).
Consequently, there is no need to infer an 'omniscient' unconscious
which is superior to conscious processing when the situation is complex.
What appears to be a problem of overconfidence in deciding with
experiential criteria that information has been processed unconsciously
is then decomposed by Kihlstrom by means of the analysis of Shanks and
St. John (1994). They identify two failures of experimenters
investigating implicit learning: most demonstrations of implicit
learning do not meet the information criterion (they fail to show that
the information the experimenter is looking for in the awareness test is
indeed the information responsible for performance changes), and they
also do not meet the sensitivity criterion (they fail to show that the
awareness test is sensitive to all the relevant conscious knowledge).
For Kihlstrom, studies in implicit learning have provided an example of
a first major problem psychologists have encountered in their dealings
with the psychological unconscious: the problem of an omniscient
unconscious. Evidence for a second major problem psychologists have
encountered in dealing with the unconscious is also discussed: the
problem encountered by those who limit the unconscious to the unattended
and unprocessed. The same review (Shanks & St. John, 1994) is used by
Kihlstrom because it provides evidence for this second problem, which
consists in limiting the unconscious to the non-processed, despite the
fact that subliminal perception studies and anesthesia studies suggest a
processing - probably essentially perceptual processing - of
environmental events. The impact of these two major problems is
highlighted by results in the fields of implicit learning, anaesthesia
and subliminal perception. Kihlstrom offers a third approach and
outlines a plausible assumption: unconscious perception - perception
without awareness of what is perceived - can occur, but it is almost
certainly limited to what can be accomplished with elementary, automatic
processes.
At least from the point of view of a cognitive psychologist, Kihlstrom's
review makes a very important point which should be developed in any
scientific analysis of consciousness: a scientific approach to
consciousness should be firmly grounded in the cognitive literature on
automaticity. It is rather clear that 'what causes automaticity' forms
at least part of any answer to 'what causes consciousness'.
4. What are the Functions of Consciousness?
Concerning this question, the book reflects an important debate between
some of the contributors in another context several years ago. The
epiphenomenalism proposed by Velmans in a target paper (Velmans, 1991) -
the claim that consciousness has no functional role - has been
critically discussed (see for example the comments by Baars and Block
appearing along with the target article), but this epiphenomenalism was
restricted to third-person accounts. When replying to Baars and other
commentators who considered that he was supporting epiphenomenalism,
Velmans (1991) indicated that although there exists substantial evidence
in support of epiphenomenalism, this evidence appears from a third-
person, external observer perspective. He added that things look
different from a first-person perspective, and that this difference is
"an apparent paradox any theory of mind must offer to resolve" (p. 713).
So the treatment in the book of the question of the function(s) of
consciousness is consistent at least with those parts of the book which
emphasise first-person accounts of consciousness.
In their chapter, Baars and McGovern compare the ways consciousness is treated within several cognitive models, including Johnson-Laird's Operating System model (Johnson-Laird, 1988), Schacter's Dissociable Conscious Experience model (DICE) (Schacter, 1990), Shallice's Information Processing Model of Consciousness (Shallice, 1988), and Baars' Global Workspace theory (GW) (Baars, 1988). Among the selected models, two (Schacter's model, Shallice's model) are clearly inconsistent with epiphenomenalism, even if epiphenomenalism should be restricted to third-person accounts. In these models, the primary function of consciousness is to mediate voluntary action under the control of an executive. Schacter's model (DICE) gives consciousness an information processing role in integrating the output of specialised modules and transmitting them to an executive system. The picture is similar (although more complex) in Shallice's information processing model of consciousness. Here the output of specialized processors is not only integrated by the supervisory system but is also integrated with control systems other than the supervisory. Moreover, at the end of their chapter, Baars and McGovern outline eight functions of consciousness: definitional and context-setting, adaptation and learning, prioritizing and access control, recruitment and control of mental and physical actions, decision-making and executive, error detection and editing, reflection and self-monitoring, and optimizing the trade-off between organization and flexibility. All of this is surprising given Velmans' views as expressed in 1991: although the book could have been expected to consider the major idea that consciousness has no causal role in information processing, it turns out that consciousness has a causal role in information processing in the models referred to. Defining the functions of consciousness is not surprising if consciousness has a functional role when viewed from first-person perspectives. It is even consistent with the general emphasis the book seems to place on first-person perspectives. But one may note that the question of the functions of consciousness is here being addressed using cognitive models which are third-person descriptions. As a result, the relevance of the question of the functions of consciousness in this book >> see note 2 << is not clear for the reader who had been convinced by Velmans' (1991) argument that (all) third-person accounts support epiphenomenalism.
More generally, the emphasis in the book on first-person perspectives
can be questioned in a number of ways: the epiphenomenalism consistent
with third-person accounts is perhaps not developed enough, the
coordination between first- and third-person methods could have been
discussed by considering a difference between the two types of methods,
and the cognitive models reviewed should sometimes use third- rather
than first-person accounts. In addition, third-person accounts have
traditionally provided information directly relevant for different
subproblems discussed in this book: how capacity limitations may be
conceived, to what extent dissociations do or do not indicate the
operation of functionally independent systems or processes. Finally,
when they suggest which processes mediate conscious experience,
third-person accounts also contribute to the answer some authors have
provided to the first of the four questions outlined at the beginning of
the book and used for structuring this review. I will now discuss these
issues, grouping my remarks in five points.
5. Some Remarks and Questions
I shall submit remarks and questions related to some difficulties I had
as a student of the cognitive approach to consciousness when reading
this book. First, two important ideas (Velmans, 1991; this book) exposed
in the introduction are not well reflected by the contributions. Second,
and related, the critical attitude towards third-person methodologies
generally adopted in the book is not entirely convincing because the
relative benefits of first-person and third-person methods differ as a
function of the type of events (conscious vs. unconscious events) that
studies want to assess. Here I will return to a chapter (Gardiner) which
is representative of the sort of critical attitude towards third-person
measures we can find in this book: the need to supplement third-person
accounts with first-person accounts of consciousness. I have previously
indicated that both the interests and limits of third-person methods of
consciousness are clearly indicated in this chapter. Consequently, I
hope it will be clear that I do not think that this (or any other)
chapter denies the value of a third-person approach; what I am
discussing is the emphasis the book places on first-person approaches.
Third, the presentation of cognitive theories of consciousness (e.g.,
Baars & McGovern), which reflect a modularity and independence approach
to consciousness, raises an important logical problem concerning the
status dissociations may have. Fourth, I wonder if the cognitive
literature has been sufficiently covered with respect to the limitations
of consciousness, and consequently, fifth, I wonder if a processing
explanation of consciousness has been sufficiently developed.
(1) I was much interested in two ideas previously developed by Velmans
(1991) and I looked for them in this book, mostly in vain. The first
idea is that introspective access, or consciousness of the results of
cerebral processing, must not be confused with the operation of that
processing. What enters awareness follows the processing to which
awareness is related and cannot therefore enter into it. This applies to
all information processing stages, whether the information is simple or
complex, familiar or novel, whether the processing is data driven,
conceptually driven or a combination of the two. As shown by the
presentation of the Baars and McGovern article, which strongly militates
against epiphenomenalism, perhaps this position is not developed enough
in the book. The second important idea is that information processing
models view the brain from an external observer's third-person
perspective, which cannot encompass the subject's first-person
perspective. These two perspectives appear to be complementary and
mutually irreducible. This second point is important because it is in
tension with the idea of a science of consciousness: science usually
redescribes the way the world seems to us from our first-person
perspective in the objective terms of a third-person perspective. Again,
between chapters 1 and 9, I had some difficulty in finding many
arguments which were consistent with this proposition in the different
contributions. The chapter by Gardiner is perhaps the only one which
provides clear references to such a co-ordination. I will briefly return
to an example of co-ordination in the following paragraph.
(2) Now, and this is related, let us re-examine the book's critical
attitude toward third-person perspective methodologies. With respect to
previous books (e.g. Roediger & Craik, 1989), I feel this book generally
argues for supplementing third-person methods with first-person methods.
I am not entirely convinced that this attitude is justified, because the
relative benefits of first-person and third-person methods differ as a
function of the type of events (conscious, unconscious events) that
studies want to assess. Two additional observations are also worth
making: the two sorts of methods can sometimes be associated; and
considering the models discussed in the book, in some cases it might
even be more logical to use third-person methods.
Gardiner criticizes two important methods that pertain to third-person
perspective methodologies: the retrieval intentionality criterion
(Schacter et al., 1989, explained above in the first section), and the
process dissociation procedure (Jacoby, 1991), in which cognitive
control in retrieval is measured by alternately placing subjects in
inclusion and exclusion conditions during a word stem completion task.
For some word stems, subjects are instructed to complete the stem with
words from the study list (or with any words that come to mind if they
cannot). This is the inclusion condition. For other stems, subjects are
instructed to not complete the stem with studied words but to complete
the stem in order to form a word which has not been studied. This is the
exclusion condition. Inclusion and exclusion conditions give two
probabilities of completing a word stem with a studied word, and these
two probabilities reflect cognitive control in retrieval: if the
probability of retrieving a studied word when 'trying to' is the same as
the probability of retrieving a studied word when 'not trying to', then
cognitive control is null. The process dissociation procedure is a
second example of third-person methods. It is important to note that the
use of third-person methods does not contradict the assumption that
first-person methodologies are the best indicator of one's awareness.
Rather it contradicts the assumption that unconscious events can be
adequately assessed with first-person methods. After all, the literature
on implicit learning has given us clear examples over the years of the
difficulty of identifying "unconscious" states on the basis of
experiential measures (see Kihlstrom, chapter two). The essence of my
remark is the following: unconscious states are best assessed with
third-person methods, as shown by the rationale behind the retrieval
intentionality criterion and the process dissociation procedure. In
addition, one may note (as does Gardiner) that third- and first-person
methods can sometimes be associated. For example, conceptual
manipulations at study (e.g., read versus generated words) are known to
affect subsequent explicit but not implicit retrieval (a third-person
method). But they are also known to affect "remember" but not "know"
responses (Gardiner, 1988), a first-person method in which subjects
indicate when recognizing a word whether or not they can consciously
recollect its prior occurrence in the study list. More generally, it is
not clear to what extent the book's emphasis on first-person methods
could be fully connected, for the moment, to current cognitive theories
dealing with consciousness. For example, rather than dealing with
awareness generally, the DICE model Schacter has put forward in recent
years deals specifically with intentionality of retrieval and awareness.
In other descriptions of the DICE model (Schacter, 1989) it can be seen
that the phenomenal awareness of remembering or 'recollective
experience' is distinct from the deliberate or intentional initiation of
retrieval, and it is the latter activity which is assigned to an
executive system distinct from the Conscious Awareness System or CAS
(see Schacter, 1989, pp. 373-374), not awareness. In fact, in DICE,
intentional initiation of retrieval is handled by the executive system
and only those activated representations that gain access to CAS can be
used by the executive system and thus influence voluntary activities.
Consequently, I wonder why DICE is discussed (Baars & McGovern) in this
book which argues against third-person methods: since intentionality of
retrieval is crucial in DICE, mediating as it does the relationship
between awareness and responses, the use of third-person methods such as
the retrieval intentionality criterion would be consistent with the
suggestion being made here that first-person and third-person methods
each have their place in studying aspects of consciousness.
(3) Do dissociations reflect the operation of functionally independent
processes or systems? In order to outline a potential logical difficulty
with dissociations, I refer again to the paper by Baars and McGovern,
one of the most integrative reviews. The description of Schacter's model
(DICE), which assumes the independence of several modules, is followed
by two major observations which are intended to support a basic idea of
DICE, that the processes that mediate conscious identification and
recognition (i.e., phenomenal awareness) should be distinguished from
modular systems that operate on perceptual, linguistic, and other kinds
of information. First, failures of awareness in neuropsychological cases
are often restricted to the domain of impairment. The fact that amnesiac
patients do not necessarily have problems reading words, while alexic
individuals do not necessarily have memory problems, is the first
argument. Second, Baars and McGovern point out that numerous examples
are known of patients with neuropsychological deficits who have implicit
knowledge without having deliberate, conscious access to that knowledge.
But do these findings "...suggest an architecture in which various
sources of knowledge function somewhat separately..." (p. 83)? This idea
seems to rely on the logic of functional dissociation. More precisely,
the form of functional dissociation used here to argue for independence
is a double dissociation: variable A affects task 1 but not task 2 and
variable 2 affects task 2 but not task 1. However, a number of papers
have shown the weakness of this logic in the area of memory (Dunn &
Kirsner, 1988; several papers in Roediger & Craik, 1989; Ostergaard &
Jernigan, 1993). Dunn and Kirsner (1988) have made clear the point that
dissociation by itself is sufficient neither to exclude the possibility
that levels of performance in two conditions depend upon the same
resource of information, nor, if it is granted that two processes are
operative, to show that each selectively affects performance on only one
condition. All that may be concluded with any certainty from measurement
of performance on two conditions (tasks, populations) is that they
depend either upon the operation of more than one process or upon more
than one source of information.
(4) Has consciousness limited capacity? Baars and McGovern point out
that many philosophers and psychologists have noted limitations on
conscious awareness: in each conscious moment we tend to be conscious of
only a single internally consistent thing (object, intention); also, the
number of items currently rehearsed in working memory is limited. Here,
the cognitive literature could have been considered in more detail. How
are the limitations on conscious awareness conceived? This important
question is addressed by the GW theory, but the reader cannot easily
evaluate why a segregation principle is used in the theory in order to
explain what enters awareness. Many theories of conscious limitations
have been proposed and they fall into (at least) two categories:
segregation models, as in the GW theory, but also processing
explanations. Processing explanations have it that the 'capacity limit'
varies as people organise incoming information, as automaticity or
experience develop. If the 'capacity limit' is known to be a function of
the subject's knowledge, it is not clear to what extent a segregation
model can explain a (putative) limit on consciousness. Stated more
clearly, consciousness may not be limited for cognitive accounts (Hirst,
1996). I have reached a similar conclusion elsewhere (Terrier, 1998) in
my efforts to identify a variable that explains (i.e., a variable that
could be responsible both for the production and the absence of) several
dissociation phenomena. This brings us to the question of which process
or processes mediate conscious experience.
(5) Which process or processes mediate conscious experience? Because the
objective of the book was (partially) to review cognitive studies, I was
interested when reading the book to discover which cognitive variable or
variables have structured the investigation of the topics considered
usual in the study of consciousness in cognitive psychology:
automaticity, implicit learning, and implicit memory. I have searched
for this characterization and have been unable to find it. As previously
noted, contributors differ in their proposals. For some, consciousness
is the product of information processing - but the processing operations
are not fully discussed. Even for those who argue that consciousness is
the product of brain activity, it appears that consciousness should also
be defined in cognitive terms (see Young, chapter 6). I think that there
are arguments for both but that there is a lack of definition of the
processing operations that produce consciousness. Because I have
recently been working in this area, I suggest the following idea
(Terrier, 1998): a common mechanism can be detected which is responsible
for what has been called implicit versus explicit learning, implicit
versus explicit memory, and automatic versus controlled processing. In
each case, consistency of mental operations over time can be shown to be
the explanatory factor: this factor is responsible for both the
production and the non production of dissociation. Consequently, a
simple but substantially empirically motivated suggestion could be
elaborated on the basis of cognitive psychology: does consistency of
mental operations over time lead to consciousness?
6. A Snapshot
To sum up, in this new book, consciousness is (mostly) awareness, and
awareness is either a product of brain activity or the result of
information processing. For some, awareness is caused by brain activity:
special neuronal populations (Libet) or a change in what neurones are
doing (Young). For others, consciousness is caused by the integration by
an executive system of information processing streams (Baars &
McGovern). In this case, the primary function of consciousness is to
mediate voluntary action under the control of a unified executive
system. However, one can assume that consciousness mediates different
cognitive activities without necessarily locating consciousness in a
unified executive system (Baars & McGovern illustrate this). The
boundary between conscious and unconscious events cannot be easily
determined, as shown by the highly specific nature of neuropsychological
impairments (Young) and the different methodological problems
researchers have faced in contrasting conscious and unconscious events
(Kihlstrom). Finally, clinical phenomena which represent other classes
of mind-body interactions (Sheikh et al., Wall) should also be
considered.
The book is clearly organised for the multidisciplinary audience of
students of consciousness. One may feel (as I sometimes do) that because
of the concise style chosen for this book empirical arguments are not
always illustrated or spelled out clearly enough. However, provided the
reader has access to the given bibliographical resources, in order to
understand the important debates the book reflects (e.g. third- versus
first-person methods), there is no doubt that Max Velmans has edited an
interesting resource which can be used as a textbook.
Notes
1. Ten years ago, considering several difficulties in attempting to
evaluate whether or not a subject is 'aware' of a prior episode during
performance of an implicit test of memory, Schacter, Bowers and Booker
(1989) argued that it was preferable to distinguish between explicit and
implicit memory in terms of intentional vs. unintentional retrieval
processes - rather than in terms of the presence or absence of conscious
recollective experience - because we can develop rigorous criteria for
making the former, but not the latter, distinction. A two component
empirical test for making this distinction was put forward: the
retrieval intentionality criterion. First, cues provided to subjects
during implicit and explicit tests should be the same, and only test
instructions should vary. Second, an experimental manipulation should be
identified that selectively affects performance on one of these tasks
and not the other. Once researchers have identified an experimental
paradigm that satisfies both of these conditions, they can begin to use
the data generated to make inferences about the nature of implicit
versus explicit memory.
2. I recognize that this observation primarily applies to the chapter
under discussion. However, since this chapter is basically the only one
which deals with the question of the functions of consciousness, I feel
that the observation made about the chapter can be taken as a conclusion
for the book without too much distortion. This strategy is the one I
have tried to follow in examining to what extent the reader can find the
answer(s) in the book to the questions outlined in the introduction.
Acknowledgements
The author would like to thank Max Velmans for comments on a draft of
this review, and gratefully acknowledge the editorial assistance of
Steve Gardner in preparing the review for publication.
References
Baars, B.J. (1988). A cognitive theory of consciousness. New York:
Cambridge University Press.
Baars, B.J. (1994). A thoroughly empirical approach to consciousness [80
paragraphs]. PSYCHE [on-line journal], 1(6). URL:
http://psyche.cs.monash.edu.au/v1/psyche-1-06-baars.html
Dienes, Z., Broadbent, D.E., & Berry, D.C. (1991). Implicit and explicit
knowledge bases in artificial grammar learning. Journal of
Experimental Psychology: Learning, Memory, and Cognition, 17,
875-887.
Dulany, D.E., Carlson, R.A., & Dewey, G.I. (1984). A case of syntactical
learning and judgment: How conscious and how abstract? Journal of
Experimental Psychology: General, 113, 541-555.
Dulany, D.E., Carlson, R.A., & Dewey, G.I. (1985). On consciousness in
syntactic learning and judgment: A reply to Reber, Allen, and
Regan. Journal of Experimental Psychology: General, 114, 25-32.
Dunn, J.C., & Kirsner, K. (1988). Discovering functionally independent
processes: The principle of reversed association. Psychological
Review, 95, 91-101.
Gardiner, J.M. (1988). Functional aspects of recollective experience.
Memory and Cognition, 16, 309-313.
Hirst, W. (1996). Cognitive aspects of consciousness. In M.S. Gazzaniga
(Ed.), The cognitive neurosciences (pp. 1307-1319). London: MIT
Press.
Jacoby, L.L. (1991). A process dissociation framework: Separating
automatic and intentional uses of memory. Journal of Memory and
Language, 30, 513-541.
Johnson-Laird, P.N. (1988). A computational analysis of consciousness.
In A. Marcel and E. Bisiach (Eds.), Consciousness in contemporary
science. Oxford: Clarendon.
Matthews, R.C., Buss, R.R., Stanley, W.B., Blanchards-Fields, F., Cho,
J.R., & Druhan, B. (1989). Role of implicit and explicit processes
in learning from examples: A synergistic effect. Journal of
Experimental Psychology: Learning, Memory, and Cognition, 15,
1083-1100.
Ostergaard, A.L., & Jernigan, T.L. (1993). Are word priming and explicit
memory mediated by different brain structures? In P. Graf & M.E.J.
Masson, (Eds.), Implicit memory: New directions in cognition,
development, and neuropsychology (pp. 327-349). Hillsdale, N.J:
Erlbaum.
Perruchet, P., & Pacteau, C. (1990). Synthetic grammar learning:
Implicit rule abstraction or explicit fragmentary knowledge?
Journal of Experimental Psychology: General, 119, 264-275.
Perruchet, P., & Pacteau, C. (1991). The implicit acquisition of
abstract knowledge about artificial grammar: Some methodological
and conceptual issues. Journal of Experimental Psychology:
General, 120, 112-116.
Roediger, H.L. III, & Craik, F.I.M. (1989). Varieties of memory and
consciousness: Essays in honour of Endel Tulving. Hillsdale, NJ:
Erlbaum.
Schacter, D.L. (1989). On the relation between memory and consciousness:
dissociable interactions and conscious experience. In H.L. Roediger
III & F.I.M. Craik (Eds.), Varieties of memory and consciousness:
Essays in honour of Endel Tulving (pp. 355-389). Hillsdale,
NJ:Erlbaum.
Schacter, D.L. (1990). Toward a cognitive neuropsychology of awareness:
implicit knowledge and agnosia. Journal of Clinical and
Experimental Neuropsychology, 12, 155-178.
Schacter, D.L., Bowers, J., & Booker, J. (1989). Intention, awareness,
and implicit memory: The retrieval intentionality criterion. In S.
Lewandowsky, J.C., Dunn & K. Kirsner (Eds.), Implicit memory:
Theoretical issues, pp. 47-65. Hillsdale, N.J: Erlbaum.
Shallice, T.R. (1988). Information-processing models of consciousness:
possibilities and problems. In A.J. Marcel and E. Bisiach (Eds.),
Consciousness in contemporary science. Oxford: Clarendon.
Shanks, D.R., & St. John, M.F. (1994). Characteristics of dissociable
human learning systems. Behavioral and Brain Sciences, 17,
367-447.
Terrier, P. (1998). Re-examining the role of consistency: The
cornerstone, not simply an important factor. PSYCHE [online
journal], 4(5).
URL: http://psyche.cs.monash.edu.au/v4/psyche-4-05-terrier.html
Velmans, M. (1990). Consciousness, brain, and the physical world.
Philosophical Psychology, 3, 77-99.
Velmans, M. (1991). Is human information processing conscious?
Commentaries and author's response. Behavioral and Brain Science,
14, 651-726.
