Consciousness: Creeping up on the Hard Problem
Book review of Jeffrey Gray’s Consciousness: Creeping up on the Hard Problem. The late Professor Emeritus Jeffrey Gray is one to be remembered well. He is known for many things, including being one of the most highly cited experimental psychologists in the UK to generating theories of human consciousness. (See the obituary by Nick Rawlins). […]
Book review of Jeffrey Gray’s Consciousness: Creeping up on the Hard Problem. The late Professor Emeritus Jeffrey Gray is one to be remembered well. He is known for many things, including being one of the most highly cited experimental psychologists in the UK to generating theories of human consciousness. (See the obituary by Nick Rawlins). This book is the culmination of Gray’s long-standing quest for understanding the essential properties of consciousness.
Although many topics are covered in Gray’s final book, a few common threads run through it. Gray returns again and again to the fact that consciousness lags behind stimulus and response. He argues this proves that unconscious servomechanisms mediate our actions. Prompted by this paradox, Gray probes: Do we need consciousness at all? Is it epiphenomenal? After much consideration, he concludes that consciousness does serve a very important purpose.
The purpose proposed by Gray is late error detection, with consciousness serving the role as comparator. He restates the comparator model that he first published in 1995 in Behavioral and Brain Sciences (a journal for which Gray was the one of Do we need consciousness at all? Is it epiphenomenal? the distinguished editors) and later elaborated upon with Neil McNaughton in their book The Neuropsychology of Anxiety published in 2000. Consciousness lags behind the onset of a stimulus by a few hundred milliseconds. This makes it an ideal comparator system, evaluating outcomes with predicted outcomes. If there is a match, then the brain does not get too excited; however, if there is a mismatch the brain responds and corrects the error often the next time the stimulus is presented. Gray goes on to explain situations in which this theory works well and situations in which it falls short.
In addition to his own theory, Gray ponders a number of other key theories and pieces of evidence on consciousness. He is searching for insights, forever the gatherer of information looking for ideas to improve upon his own thesis. He analyzes Searle’s model wherein consciousness is a macro-property emerging from micro-elements (the former deduced from the latter). He reviews Dennett’s multiple drafts model. Gray spends a good deal of time going over Stevan Harnad’s model for categorical representation. Intriguing examples, such as synesthesia, blindsight and phantom limb pain are sprinkled throughout the book bolstering Gray’s various arguments. In particular, Gray argues that synesthesia precludes a strict functionalist explanation of consciousness.
Later in the book, Gray applauds neuroscientists Colin Blakemore and Susan Greenfield for breaking the dam, so to speak, and publishing on the taboo subject of consciousness in their 1987 book Mindwaves. He gets to the heart of the problem that neuroscience used to gloss over consciousness, frequently writing it out of the story altogether.
Gray devotes an entire chapter (and then some) to global workspace theory. This theory developed by Bernard Baars and elaborated upon by others has many attractive features (seven are enumerated by Gray). One issue Gray raises, however, is the importance of uncovering the neural underpinnings that are essential to global workspace theory.
Visual consciousness has a particular place in consciousness, if for no other reasons than the vivid visual experiences we have and the large amount of cortical mass devoted to this sense. Gray elaborates on several features of visual Gary argues that synesthesia precludes a strict functionalist explanation of consciousness. consciousness. He comes to agree with Crick and Koch that V1 is not essential for consciousness, but disagrees that the frontal lobe is essential. Summarizing Zeki’s work on color vision, Gray points out that individual conscious components, such as color, may well involve a single cortical area, such as V4 (or V8 in the human brain). Hence conscious entities turn out not to be perfectly unified after all!
A primary focus of Gray’s book, as spelled out in the book’s very name, is to tackle the hard problem of consciousness, a term originating with David Chalmers. In search of a possible solution to the hard problem, Gray delves into the Penrose and Hameroff quantum physics model of consciousness. Gray does an excellent job at describing this model, thereby making it accessible to many who may not have fully appreciated the degree to which this quantum physics model of consciousness is internally consistent.
Gray’s book is well worth the read. His coverage of models that address the hard problem of consciousness is reasonably complete. Gray is highly skilled at thoroughly critiquing each model (always finding both strengths and weaknesses). He gives the same constructive criticism to each model, in exactly the same measure he gives his own. His style is entirely fair-minded and refreshing.
I, for one, agree with most aspects of Gray’s comparator model wherein consciousness serves in late error detection, especially the next time a stimulus is presented. One potential point missed by Gray (but perhaps alluded to) is that consciousness may, in some instances, provide a representation of the stimulus-response. As Gray astutely argues in matters of brain, everything is a representation.
Regarding global workspace theory, Gray seems to have missed that certain cholinergic and monoaminergic ascending projection neurons, which are known to play roles in consciousness, have a global anatomical organization (see Woolf, 1996). These global neurons, which project diffusely upon cerebral cortex, might complement and expand upon the actions of the thalamocortical systems and strengthen the neuroanatomical basis for the theory.
All in all, Gray’s selection of material is well balanced. As the title suggests, the fundamental essence of consciousness, or the hard problem, is the main thrust of the book. Thus, the selection of material is dictated by that focus and Gray does a brilliant job discussing even the most difficult of topics. This is an excellent book that comes at the conclusion of the life of an outstanding member of academia. It is a timeless addition to any library for this reason alone.
References
- Gray, JA. (1995) The contents of consciousness: A neuropsychological conjecture. Behavioral and Brain Sciences, 18:659-722.
- Woolf NJ. (1996) Global and serial neurons form a hierarchically arranged interface proposed to underlie memory and cognition. Neuroscience, 3:625-51.
