In his book 'Consciousness: Creeping up on the Hard Problem' written towards the end of his life, Gray summarised his ideas about brain function and consciousness. He took the view that the contents of consciousness are usually about something, and this is described as intentionality or meaning. He suggested that intentionality is another aspect of the 'binding problem', as to how the different modalities, such as sight and hearing, are bound together into a single conscious experience. Gray argued that without such binding, eating a banana could involve seeing yellow, feeling a surface, and tasting something, without having the unifying awareness of a particular object known as a banana. Without such unifying binding, he argues that objects would be just meaningless shapes, edges, colours etc.

Gray thought that intentionality was based on unconscious processing. The processing in the visual cortex that underlies conscious perception is not itself conscious. Instead, the perception is argued to spring into consciousness fully-formed, including the intentionality of what the conscious perception is about. In arguing for this, Gray uses the example of pictures that can be either of two things, such as a duck or a rabbit. They are never hybrid, but are always completely duck or completely rabbit. The perception of a duck or a rabbit is argued to be constructed unconsciously up to the last moment. Gray's conclusion from this part of his discussion is that intentionality arises from the physical and chemical structure of the brain, but also that if intentionality can be constructed out of unconscious processing, it is unlikely to produce a solution to the 'hard problem' of how consciousness arises.

Gray was opposed to the idea that the brain contains a representation of the external world. He considered that the external world, as described by physics, is nothing like what it appears to be in conscious perception. He also dismissed, what he called the 'fall back position', which is to think that the perception of something, a cow for example, is a representation, in the sense of resembling a cow as it really exists. Gray argued that our only direct knowledge of the cow is a brain state. We have no direct knowledge of the cow as it really is, and it is meaningless to say that the cow brain-state is a representation of the real cow.

Instead, Gray thought that conscious perceptions should be treated as signals. Signals have no need to resemble the thing about which they communicate. A whistle might warn thieves of the approach of a policeman, but a whistle is nothing like a policeman. Perceptual experiences are seen as signals, about what observers might expect about their environment. However, he stressed that these perceptual signals arise in the brain, and do not have any kind of external existence. This is not to say that we cannot deduce useful information about the visual world from perception. Thus, for example, in his view, visual perception is a good guide to the reflectance of surfaces, which in turn often have survival value for the organism. Gray took the view that in investigating consciousness, discussions about intentionality and representation should be discarded, and research should be concentrated purely on qualia or subjective experience, as being the only aspect of the brain that involves consciousness.

Gray viewed the function of consciousness as a 'late error detector'. The brain was argued to be a 'comparator system' that predicts what should happen, and detects departures from that prediction. It was suggested that consciousness is particularly concerned with novelty and error. He also viewed it as something that causes us to review past actions, and to learn from errors in these actions. Late-error detection permits more successful adaption, if a similar situation emerges in the future. In respect of this, Gray looks at the example of pain. We remove our hands from a hot surface, before consciously feeling the pain of touching it. The pain involved is argued to be a rehearsal of the action that led to it, and has the survival advantage of making a repetition of the damaging action less likely.

Gray accepted that there are many unconscious systems that detect errors, so this on its own does not establish a survival value for consciousness. However, he distinguished consciousness as being multi-modal, and as directing us towards whatever is most novel within several modalities. The brain was argued to take account of plans as to what to do next, plus memories of past regularities, in assessing what is likely to be the next stage of a particular process. These predictions are submitted to a comparator, but still at an unconscious stage. Only the unexpected outcomes, or feedback for the continuation of motor action enters consciousness.

Gray regarded consciousness as a medium of display created by unconscious processing. He argued that the conscious display is used by unconscious systems, as in the example given of unconscious aversion to a food associated with a gastric illness. Conscious perception is in this theory created by unconscious systems, and used by other unconscious systems to respond to late errors, unexpectedness or novelty.

Gray likened conscious perception to a sketch made of a particular scene that is retained for use as a record or reminder of that scene. In this way, the sketch is causal in the sense that it performs the function of recalling or assisting memories, but it is not directly active in the brain. In Gray's consciousness model, the conscious perception plays much the same role as the sketch in his analogy. Consciousness is causal, in the sense that downstream unconscious systems respond to it, mainly in the area of error correction. However, this conscious aspect of the brain has no agency or freewill, with which to initiate or inhibit actions, anymore than the sketch on a piece of paper can initiate actions independently.

Gray disagreed with the functionalist theory of consciousness. He described the position of functionalism as saying that consciousness is the nature of certain complex systems, regardless of whether they are made of neurons, silicon chips or some other material. The underlying tissues or machinery are irrelevant. Further to that consciousness relates only to functions performed by the brain or other system, and does not arise as a result of anything that is not functional. For any discriminated difference in qualia, there must be a difference in function. It is also claimed that for every discriminated difference in function, there is a difference in qualia.

In discussing this question further, Gray looked at synaesthesia, where he described modalities as becoming mixed, as when numbers or sounds are experienced with colour. Experimentation in recent years has demonstrated that synaesthesia is most likely the consequence of abnormal projections into the V4 colour region of the visual cortex from other parts of the brain. Brain scanning studies have shown that when words are spoken, in addition to the normal activity in the auditory cortex, the V4 colour vision area in the visual cortex became active, in a way which does not occur in normal subjects. There was no related activation in V1 or V2, the earlier stages of the visual pathway. The conclusion drawn from a whole series of experiments was that the 'word-type' of synaesthete has an abnormal projection from the auditory cortex into the visual cortex causing the V4 colour area to produce consciousness of colour. However, there is no evidence that this colour sensation has any function.

Gray argued from these findings that there was no relationship between the occurrence of the synaesthete's colour experience and the linguistic function that triggers them. Gray argues that this phenomena refutes the functionalist analysis of consciousness, because the theory claims that conscious experience relates only to functions performed in the brain, and does not arise as a result of anything that is not functional, as is claimed to be the case with this type of synaesthesia.

Gray also discussed the Penrose/Hameroff Orch-OR theory of consciousness. His main objection to this is the question as to why particular wave function collapses should select for one particular qualia. He also questions the temporal aspect of Hameroff's model, where the proposed 25 milliseconds to wave function collapse is only a tenth of the time considered necessary for a conscious perception to form.

Books

• Gray, J. A. (1964). Pavlov's Typology. Elsevier ISBN 0-08-010076-7
• Gray, J. A. (1987). The neuropsychology of anxiety. OUP. ISBN 0-19-852127-8
• Gray, J. A. (1987). The psychology of fear and stress (2nd ed.). Cambridge:

Cambridge University Press.

• Gray, J. A., & McNaughton, N. (2000). The neuropsychology of anxiety (2nd ed). (Revised version with theoretical implications)
• Gray, J. A. (2004). Creeping up on the hard problem OUP. ISBN 0-19-852090-5

Book Chapters

• Gray, J. A. (1981). A critique of Eysenck's theory of personality. In H. J. Eysenck (Ed.), A model for personality (pp. 246—276). New York: Springer.
• Gray, J. A. (1994). Framework for a taxonomy of psychiatric disorder. In S. H. M. van Goozen, & Van de Poll,Nanne E. (Eds.), Essays on emotion theory. (pp. 29—59). Mahwah, NJ: Lawrence Erlbaum Associates, Inc.

Papers

• Gray, J. A. (1970). The psychophysiological basis of introversion-extraversion. Behaviour Research & Therapy, Vol. 8(3), 249-266.
• Gray, J. A. (1990). Brain systems that mediate both emotion and cognition. Cognition & Emotion, 4(3), 269-288.
• Gray, J. A. (2002) Implications of synaesthesia for functionalism: theory and experiments Journal of Consciousness Studies 9 (12), 5-31
• Nunn, J. A. et al. (2002) Functional magnetic resonance imaging of synaesthesia: activation of V4/V8 by spoken words

Nature Neuroscience 5, 371-5

• Baron-Cohen, S. et al. (1993) Coloured speech perception: is synaesthesia what happens when modularity breaks down? Perception, 22, 419-26
• Quantum-mind

Critiques

• Higgins, E. Tory (1997). Beyond Pleasure and Pain. American Psychologist, 52(12), 1280-1300.