research now being done around the globe on autism, and one volume is just not large enough to holdall of the important findings and ideas currently being published. Therefore, more special issues andcollections of research about ASDs are warranted. Another possible limitation is the price. At £29.95(about $55.00 US) it is somewhat high for a paperback. But since it’s likely to be purchased mainlyby professionals and institutions, and given the quality of the papers involved, I think this representsgood value for the money.

REFERENCES

Baron-Cohen, S. (2003a). The essential difference: Men, women and the extreme male brain.London: Penguin Books.

Baron-Cohen, S. (2003b). A mature view of autism. Trends Cognitive Sciences, 7, 380–383.Frith, U. (2003). Autism. Explaining the enigma (2nd ed.). Oxford: Blackwell.Happe, F. (1999). Autism: cognitive deficit or cognitive style? Trends in Cognitive Sciences, 3, 216–222.

CHRIS ASHWINAutism Research Centre, University of Cambridge, UK

Published online in Wiley InterScience(www.interscience.wiley.com) DOI: 10.1002/acp.1060

How to consider the unity of consciousness?

THE UNITY OF CONSCIOUSNESS: BINDING, INTEGRATION AND DISSOCIATION. A.Cleeremans (ed.). Oxford University Press, Oxford, 2003. No. of pages 314. ISBN 0-19-850857-3.Price £35.00 (hardback).

It is generally accepted that consciousness is unified: that phenomenal experience exists as a whole,in which all elements appear to belong to a spatial and temporal continuity. This book exploresvarious ways of thinking about the unity of consciousness. The distinguished contributors offer awide spectrum of views ranging from abstract philosophical arguments to detailed consideration ofhow the various aspects of an object or event, processed in separate areas of the brain, are integratedinto a unified representation (the binding problem). Following Axel Cleeremans excellent introduc-tion and summary of the contents, the book is divided into four roughly thematic sections.

The first section contains three papers discussing what it means for consciousness to be unifiedand whether partial unity may be possible. Bayne and Chalmers make a conceptual distinctionbetween an access-conscious state (one that is available for verbal report) and a phenomenal-conscious state (there is ‘something it is like’ to be in the state). They argue that all of a subject’sphenomenal-conscious states at a given time are necessarily unified, in that there is ‘something it islike’ to experience the conjunction of all the phenomenal states. In contrast, partial unity of access-consciousness is deemed plausible: a subject may be able to report on either of two statesindividually but not their conjunction. Shoemaker takes a different approach, defining consciousnessholism as the view that the factors that go into making a particular mental state conscious (e.g. itsaccessibility for integration with other mental states) are inextricably intertwined with those that gointo constituting a unified state of consciousness (a set of mental states are all mutually accessible).Consciousness atomism is the denial of this view, and Shoemaker argues against different types ofconsciousness atomism (e.g. higher-order thought theory) to conclude that consciousness requiresunity of consciousness. Whereas these two chapters make much use of the concept of ‘what it is like’to have a conscious experience, Hurley rejects this as a way of thinking about partial unity ofconsciousness. She concentrates instead on using specific empirical studies to develop the motor-dependence hypothesis, which states that perceptual experience depends on motor intentions andactions as well as on received sensory information. In this view, consciousness and the unity of

Copyright # 2004 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 18: 931–940 (2004)

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consciousness may depend on a temporally extended feedback process connecting motor intentionswith sensory input, and so in a very short temporal interval, partial unity may be apparent in theexperience and behaviour of experimental participants.

Section 2 explores how distinct aspects of an object or event processed in separate brain regionscan be bound into a unified representation. All concur that binding is necessary but not sufficient forconsciousness. Triesman and Humphreys both present chapters suggesting that early stages ofbinding are parallel and non-conscious, and that serial attention is necessary to produce a final boundobject representation that can enter awareness. The papers by Engel and Tallon-Baudry reviewdetailed evidence that the temporal synchronization of neural firing in different brain regions resultsin the integration of object features coded in those regions into an single object representation. Incontrast, O’Reilly, Busby, and Soto note that there are problematic limitations of temporal synchronyas the mechanism of binding (briefly discussed also by Engel). They argue that there are severalsolutions to the binding problem addressing the different requirements of binding in different parts ofthe brain: basic perceptual binding in the cortex; binding the distinct elements of an event into aspecific episode in the hippocampus; and phonological encoding in the prefrontal cortex. Mechan-isms of binding seem likely to be a key area for future debate (and Rolls & Deco, 2002, may also beof interest).

Section 3 When unity breaks down, contains three chapters that all address, in different ways,the issue of whether consciousness and unconscious knowledge must be unified—whether arepresentation of which one is conscious must necessarily be unified with unconscious mentalstates. Perruchet and Vintner propose a controversial self-organizing consciousness model thatexplains how properties of consciousness and attention (e.g. limited capacity, rapid forgetting) causethe contents of consciousness to become increasingly isomorphic to the world. Thus, consciousnessis seen as sufficient for learning and adaptive responses. This contrasts with the view that learningtakes place unconsciously and that only the outputs of learning become accessible to consciousness.The self-organizing consciousness model may be speculative, but it does define a fundamentalfunctional role to the unity of consciousness, rather than regarding it as something to be explained.Dienes and Perner offer an analysis of knowledge as implicit or explicit to varying degrees. Theyargue that fully explicit knowledge corresponds to conscious knowledge, building a link with higher-order thought theory. Considering that increases in explicitness of knowledge are necessarilyassociated with greater unity of knowledge, this implies that conscious knowledge must be unifiedwith co-conscious knowledge. However, in contrast to Perruchet and Vintner, Dienes and Pernerargue that causally effective unconscious knowledge may be disunified with conscious knowledge.This view would seem to be supported by Young in his paper on prosopagnosia, a classicaldissociation of conscious and unconscious knowledge, in which recognition of known faces may bemanifest in a covert test simultaneous with a complete absence of awareness of facial familiarity.

Section 4 Integration: The emergence of unity, looks at the neural basis of the unity ofconsciousness. Tononi considers that a conscious state presents integrated information, generatedwhen an integrated system occupies a particular state. So the question is, what physical system cangenerate the integrated information that is contained in a conscious experience? Tononi develops ameasure of the information represented in a system (MIDC) and goes on to propose that thethalamocortical system is a prime candidate for the system underlying unified consciousness, beingboth highly integrated, with multiple connections and feedback loops, and highly differentiated,capable of occupying a huge number of meaningful states. Varela and Thompson consider the causalefficacy of consciousness in the context of reciprocal causation, that is, both local-to-globalemergence of complex representations from local neural assemblies, and a global-to-local emergentprocess that allows the modulation of local neural activity by the whole dynamic system. They takethe view that consciousness and its unity arise at the level of the neural and mental processesembodied in the whole person interacting with the environment, and so the unity of consciousnessmust be explained in both phenomenological and neural terms at this level. Coterill notes thatconsciousness is always an active process, and reasons that consciousness and attention requireactivity in the motor planning area of cortex. Considering the role of schemata in perception andlearning, he suggests that the dependence of perception on activation of the appropriate schema mayexplain the half second delay before a percept becomes conscious that was observed by Libet et al.(1991). In simple terms, when a schema is active, and is attended to, there is a conscious percept.Coterill takes the bold position that the motor cortex controls the nervous system and must thereforebe responsible for the unity of consciousness.

Copyright # 2004 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 18: 931–940 (2004)

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Each of the chapters in this book makes a distinct contribution to the questions posed by the unityof consciousness. On the down side, there is little integration between the different levels ofdiscussion contained in different sections, e.g. section 2 focuses on the binding of object featureswhile section 1 examines the unity of consciousness at the level of the whole conscious fieldexperienced by the subject. Generally, the concept of attention is given insufficient consideration,with the notable exception of the Cotterill chapter. Regarding the individual chapters, some attributecausal efficacy to conscious states, as opposed to unconscious states, without clearly justifying thisposition. While cogent arguments are presented for the adaptiveness of the unity of consciousness inpresenting a coherent view of the world that facilitates learning and integration with previousknowledge, it should be noted that this unity is likely to be a reflection of the coherent, integratedinformation represented in the neural activity of the brain at any given moment. A clear argument forthe causal efficacy of consciousness per se remains elusive. As a note of caution, several of thearguments presented in this book rely heavily on just one or two empirical studies and case studies,which support more than one explanation: the reader might be wary of drawing too strongconclusions from selective examples.

The book may be most useful for illustrating the breadth of approaches applied to the unity ofconsciousness and the different levels at which the concept can be considered. It offers few solidconclusions but raises many questions. Overall, there is much that is stimulating and thoughtprovoking, and anyone with an interest in consciousness will find something worth reading.

REFERENCE

Rolls, E. T., & Deco, G. (2002). Computational neuroscience of vision. Oxford: Oxford UniversityPress.

Libet, B., Pearl, D. K., Morledge, D. E., Gleason, C. A., Hosobuchi, Y., & Barbaro, N. M. (1991).Control of the transition from sensory detection to sensory awareness in man by the duration of athalamic stimulus. Brain, 114, 1731–1757.

ANNA STONEGoldsmith College, University of London, UK

Published online in Wiley InterScience(www.interscience.wiley.com) DOI: 10.1002/acp.1032

An outstanding introduction to forensic psychology

HANDBOOK OF PSYCHOLOGY: VOLUME 11—FORENSIC PSYCHOLOGY. A. M. Goldstein(ed.), I. B. Weiner (series ed.). John Wiley & Sons, New Jersey, 2003. No. of pages 606. ISBN0-471-38321-X. Price £93.95 (hardback).

This volume of the Handbook of Psychology series focuses on forensic psychology. This is anauthoritative text, which examines and discusses forensic practice from a research perspective. Thetext is divided into seven sections. Part one: Nature of the field gives a concise and comprehensiveintroduction to the area. It clearly delineates how the authors define forensic psychology and theirdefinition revolves around the psychology of assessment for the courts. This section also differ-entiates clinical from forensic psychology, gives an excellent outline of the ethical concerns uniqueto forensic practice, and gives an introduction to the particular roles and responsibilities of a forensicpsychologist giving expert evidence. Later chapters of the book address the more specificrequirements of expert testimony.

Part two: Approaches to forensic assessment gives three excellent, if unrelated, chapters focusingon issues relating to assessment. First, there is a detailed and critical account of all aspects ofcollecting, using and assessing third party information in a forensic assessment. Second, the myriad

Copyright # 2004 John Wiley & Sons, Ltd. Appl. Cognit. Psychol. 18: 931–940 (2004)

Book reviews 937