Gray’s Brain-Built World-Model: Qualia, Comparators, Late-Error Detection

Psychologist Jeffrey Gray’s theory treats phenomenal consciousness as a brain-built, multimodal “display” of the organism and its world, generated too slowly to direct most immediate behavior but useful for detecting failures in the unconscious systems that do. Conscious experience supplies an arena in which actual outcomes can be compared with predictions across separate perceptual and action-control systems. Gray thereby offers a naturalistic account of conscious contents and their adaptive function, while conceding that it does not explain why the relevant neural processes should feel like anything at all (Gray, 1995, 2004).

Gray approached consciousness as an experimental psychologist who had spent a career modeling the “septo-hippocampal comparator” (see below), and he brought that machinery to bear on what he insisted was the only genuine explanandum: qualia. Stripping away intentionality and representation as achievements the unconscious brain manages perfectly well, Gray argued that conscious experience is a late-arriving, brain-constructed display medium in which the outputs of unconscious computation are presented in a unified multimodal model, enabling a comparator to perform late error detection against prediction (Gray, 2004). Two empirical planks support and constrain the account: conscious percepts arrive too slowly to control online behavior, and synesthesia dissociates qualia from function in both directions, which Gray took to refute reductive functionalism (Gray et al., 2002; Gray, 2003). The title of his posthumously published book, Consciousness: Creeping Up on the Hard Problem, is a concession as much as a program, since Gray explicitly and laudably denied having solved the hard problem, claiming only to have narrowed the target by establishing what consciousness does and what it demonstrably is not.

Constructed Phenomenal Reality

Perceptual consciousness is not, for Gray, a transparent apprehension of mind-independent reality. Colors, sounds, bodily location, objects, and the apparent self belong to a simulated world constructed by unconscious neural activity; qualia are the felt properties of that construction. Conscious perceptions function less as pictures resembling external objects than as useful signals. Intentionality—experience being about a banana, face, or danger—arises when features processed in distinct pathways are unconsciously bound into unified objects before awareness. Since this organization can occur unconsciously, Gray argues that intentionality does not much affect, much less resolve, the phenomenal problem (Gray, 2004).

Qualia as the Sole Explanandum

Gray's opening move is eliminative about the problem space rather than about consciousness. Intentionality, binding, and behavioral control are all exhibited by unconscious processing; a duck-rabbit figure is resolved unconsciously and springs into awareness already interpreted. He also rejected representational construals of perception: the external world as physics describes it is nothing like the world as experienced, and conscious percepts are better treated as signals, which need not resemble what they signal. What survives this subtraction is qualia alone, and Gray held that consciousness research should concentrate on them exclusively (Gray, 2004).

The Comparator and the Function of Late-Error Detection

Gray’s affirmative theory about phenomenal consciousness extends his approach to the neuropsychology of anxiety, in which the septo-hippocampal system compares actual against predicted states and interrupts behavior on mismatch (Gray & McNaughton, 2000). Because organisms err, they require a mechanism for detecting errors after the fact, and such a mechanism needs a stable, integrated model of the environment against which predictions can be checked. Conscious experience is that model: a display medium created by unconscious systems and used by other unconscious systems, in which novelty and mismatch are made available across modalities so that servomechanisms can be adjusted for future performance (Gray, 2004; Biggs, 2005).

The “septo-hippocampal comparator” is a core neurocomputational model— developed by Gray and Russian cognitive neuroscientist O.S. Vinogradova—proposing that the brain continuously evaluates predictions against reality. The system uses the medial septum to regulate hippocampal theta oscillations. The hippocampus predicts what will happen next, and when an incoming sensory signal contradicts these expectations, the comparator detects a mismatch.

Conscious Perception Comes Too Late

The timing argument is the theory's empirical fulcrum. A visual percept requires roughly a quarter-second from retinal stimulation, too long to initiate the motor programs that return a fast tennis serve, and the dorsal stream governing visually guided action is dissociable from the ventral stream yielding visual qualia (Milner & Goodale, 1995; Gray, 2004). Qualia cannot be doing online control. Gray nonetheless resisted epiphenomenalism, citing late error detection, the smoothing of jerky sensory input, and the public consensus underwriting language, science, and aesthetic judgment. His illustrative case is pain, which typically arrives after the hand has withdrawn and functions to make repetition less likely. Even so, the display is causal only in an attenuated sense: Gray likened conscious perception to a sketch of a scene, effective as a record that downstream systems consult, but possessing no agency and unable to initiate or inhibit action. Two criticisms recur: the proposed benefits would accrue equally to an unconscious mechanism performing the same operations, and Gray held some non-linguistic animals to be conscious, which strains an account whose most distinctive functions are unavailable to them (Bacrac, 2004).

Synesthesia and the Case Against Functionalism

Gray's most-cited empirical argument against reductive functionalism came from colored-hearing synesthesia. Functionalism entails that qualitative differences track functional differences and conversely; synesthesia breaks both entailments, since the same color quale arises from functionally distinct modalities while a single input-output profile yields both auditory and visual qualia (Gray et al., 2002; Gray, 2003). Imaging showing spoken-word activation of V4 (visual cerebral cortex) without earlier visual-pathway involvement, and the opposition of synesthetic to veridical color in the alien color effect, were offered as converging evidence (Nunn et al., 2002; Gray et al., 2006). Gray reviewed Penrose–Hameroff quantum proposals seriously but objected that nothing in wave-function collapse explains why one quale rather than another is selected.

What Remains Unsolved

Gray rejected dualism, denied that identifying neural correlates would constitute explanation, and declined to claim his functional account bridges the explanatory gap. Reviewers note the residual difficulty that a display appears to require an audience, reintroducing homuncular structure (Kriegel, 2005; Biggs, 2005). His standing in the Landscape is accordingly distinctive: a rigorously neurobiological theory specifying what phenomenal consciousness is for, while insisting that why any of it is felt remains untouched.

[Note: Appreciation to George Marcus for suggesting Jeffrey Gray’s theory. George is Professor of Political Science, Emeritus, at Williams College; he is known for developing affective intelligence theory, which integrates neuroscience and psychology to explain how emotions shape political judgment and behavior.]

References

Gray, J. A. (2003). How are qualia coupled to functions? Trends in Cognitive Sciences, 7(5), 192–194.

Gray, J. A. (2004). Consciousness: Creeping Up on the Hard Problem. Oxford: Oxford University Press. (Paperback edition 2007.)

Gray, J. A., Chopping, S., Nunn, J., Parslow, D., Gregory, L., Williams, S., Brammer, M. J., & Baron-Cohen, S. (2002). Implications of synaesthesia for functionalism: Theory and experiments. Journal of Consciousness Studies, 9(12), 5–31.

Gray, J. A., & McNaughton, N. (2000). The Neuropsychology of Anxiety: An Enquiry into the Functions of the Septo-Hippocampal System (2nd ed.). Oxford: Oxford University Press.

Gray, J. A., Parslow, D. M., Brammer, M. J., Chopping, S., Vythelingum, G. N., & ffytche, D. H. (2006). Evidence against functionalism from neuroimaging of the alien colour effect in synaesthesia. Cortex, 42(2), 309–318.

Bacrac, N. (2004). Review of Consciousness: Creeping Up on the Hard Problem. Philosophy Now, 48, 44.

Biggs, S. (2005). A review of Jeffrey Gray's Consciousness: Creeping Up on the Hard Problem. PSYCHE: An Interdisciplinary Journal of Research on Consciousness, 11.

Kriegel, U. (2005). Review of Consciousness: Creeping Up on the Hard Problem. Mind, 114(454), 417–421.

Milner, A. D., & Goodale, M. A. (1995). The Visual Brain in Action. Oxford: Oxford University Press.

Nunn, J. A., Gregory, L. J., Brammer, M., Williams, S. C. R., Parslow, D. M., Morgan, M. J., Morris, R. G., Bullmore, E. T., Baron-Cohen, S., & Gray, J. A. (2002). Functional magnetic resonance imaging of synesthesia: Activation of V4/V8 by spoken words. Nature Neuroscience, 5(4), 371–375.