Avoiding the
Porsche-Driving Zombie.

by
Nigel J.T.Thomas
Woodbury University
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[Unpublished commentary on A sensorimotor account of vision and visual consciousness by J. Kevin O'Regan & Alva Noë, Behavioral and Brain Sciences, 24 (2001) 939-1031.]

Perhaps it is not too much to hope, in the light of this truly excellent exposition, review, and defense of the sensorimotor, or active, approach to perception, and of striking, newly discovered effects such as change blindness, that this conceptual framework is at last poised to replace the Cartesian (materialist or otherwise) paradigm that has now dominated scientific and philosophical thinking about perception for centuries. Perhaps, before long, perception will cease to be generally regarded as a matter of getting representations into our heads (for the spiritual or neuronal homunculus to ponder), and perceptual experience will not be thought of as the "having" of such representations (veridical or otherwise), but rather as experience of the actual physical world in which we live and act (more or less successfully). Perhaps, consciousness will no longer be conceptualized as a property somehow mysteriously attached to brain states (or even to spiritual states), but as a property of organisms as embedded in and interacting with their environments (i.e. of the organism-environment system). With all the convergent lines of research that seem to point in this direction - from the latest robotic engineering (Aloimonos, 1996; Breazeal et al., 2000) to the established research program of ecological psychology (Gibson, 1966, 1979; Stoffregen & Bardy, 2001), from the theory of imagination (Thomas, 1999) to the study of eye movements (Landy, Maloney, & Pavel, 1996; Stark & Choi, 1996), from theoretical neuroscience (Ramachandran, 1990; Churchland, Ramachandran, & Sejnowski, 1994; Cotterill, 1997, 2001) to the philosophy of intentionality (Akins, 1996; Newton, 1996) - perhaps a true scientific revolution in the theory of perception and consciousness is at hand, at least if the cadres can avoid excessive infighting and factionalism.

Nevertheless, although I can find very little in the target article with which I am much inclined to disagree, and so much that is insightful, in an enterprise of this ambition there are bound to be aspects of the framework that will need further articulation. In particular, a skeptic might well worry that the crucial but underdeveloped metaphor of mastery of the sensorimotor contingencies conceals an undischarged homunculus. However, the recently proposed perceptual activity theory of mental imagery already incorporates an outline account of cognitive structures and mechanisms to support active, intelligently directed, perceptual exploration (Thomas, 1999). Although speculative, I believe this does demonstrate at least the possibility of a fully mechanistic account of sensorimotor mastery.

By contrast, I think that O'Regan & Noë worry too much about explaining why sight differs experientially from each of the other traditional five senses: i.e. their sensorimotor alternative to the doctrine of specific nerve energies,. Their account is not exactly wrong, but I suspect the problem is one of those that will be recognized as ill-posed as the new conceptual framework develops (Thomas, 2001b).

More significantly, the proffered explanation of the qualitative nature of consciousness may beg the question. We will never solve the "hard problem" without risking some metaphysical revisionism. We are told that what-it-is-like to drive a Porsche "derives from the different things we do when we drive a Porsche, and from our confident mastery of the relevant sensorimotor contingencies". But the experience of driving, surely, comprises not only what we do as we drive, but also the myriad qualitative sensations that we feel as a result. It is not only that I know just how to turn the wheel in order to corner smoothly, but that this action results in characteristic qualitative feelings of pressure against my fingers, characteristic feelings in the "seat of my pants" (or, rather, the flesh of my buttocks, as they deform against the car seat), and characteristic vestibular sensations, experiences of visual flow, and so on. However much I may be a master of the sensorimotor contingencies of Porsche driving, however much I implicitly know (and rely upon knowing) about how my movements at the controls will affect the stimulus energies impinging on my sensory transducers, without all those qualitative experiences I would be no more than a Porsche driving zombie.

Zombies cannot really exist (Thomas, 1998), so, without qualia in the head (and I entirely sympathize with the authors' rejection of these troublesome entities), how can the sensorimotor paradigm accommodate the qualitative nature of experience? In fact O'Regan & Noë (so rich is their article) do give us the answer, but so casually that it might well be missed, despite its (perhaps unintended) metaphysical audacity. While discussing the presence and immediacy with which we perceive something as red, they say, "The redness is there, in the environment." Quite so. The active perception (or sensorimotor) framework can accommodate the qualitative by locating it out in the world, just where it seems to be (Thomas, 2001a). The redness that we experience looking at a fire engine exists not in our heads, but there on the surface of the vehicle (or, perhaps, in the optic array (Gibson, 1979), the structure of the light, around it). Active, exploratory, sensorimotor perception does not bring the redness (or some surrogate for it, some quale) into our heads, rather, it takes our minds out into the world to meet it where it lives.

This view is metaphysically audacious in two respects. Firstly, it views the conscious mind not as some receptive center locked inside the skull, but as out in the environment, together with the body; having its very being, indeed, as the structure and coherence of the body's activity (a view Aristotle would have understood, but which Descartes has made us forget). Secondly, it rejects the deeply entrenched view of colors, and other experienced qualities, as "secondary," as inner mental constructs having no existence as such out in the physical world (Thomas, 2001a). A number of contemporary philosophers do argue for the physical reality of colors (identifying them with, roughly, surface reflectances, appropriately categorized) (e.g. Hilbert, 1987; Ross, 2001). If this can be generalized to qualitative experiences of all types then the sensorimotor paradigm may enable, at last, a true natural scientific understanding of qualitative consciousness (even though no philosopher, to my knowledge, is yet investigating the ontological status of buttockal sensations).

References

Akins, K. (1996). Of sensory systems and the "aboutness" of mental states. Journal of Philosophy, 91, 337-372.

Aloimonos Y. (Ed.) (1996). Visual navigation: From biological systems to unmanned ground vehicles. Mahwah, NJ: Erlbaum.

Breazeal, C., Edsinger, A., Fitzpatrick, P., Scassellati, B., & Varchavskaia, P. (2000 July/August). Social constraints on animate vision. IEEE Intelligent Systems Magazine, 32-37.

Churchland, P. S., Ramachandran, V. S., & Sejnowski, T. J. (1994). A critique of pure vision. In C. Koch & J. Davis (Eds.), Large scale neuronal theories of the brain. Cambridge, MA: MIT Press.

Cotterill, R. M. J. (1997). On the mechanism of consciousness. Journal of Consciousness Studies, 4, 231-247.

Cotterill, R .M. J. (2001). Evolution, cognition and consciousness. Journal of Consciousness Studies, 8, 3-17.

Gibson, J. J. (1966). The senses considered as perceptual systems. Boston, MA: Houghton Mifflin.

Gibson, J. J. (1979). The ecological approach to visual perception. Boston, MA: Houghton Mifflin.

Hilbert, D. R. (1987). Color and color perception: A study in anthropocentric realism. Stanford, CA: Center for the Study of Language and Information.

Landy, M. S., Maloney, L. T., & Pavel, M. (Eds.) (1996). Exploratory vision: The active eye. New York: Springer-Verlag.

Newton, N. (1996). Foundations of understanding. Amsterdam: John Benjamins.

Ramachandran, V. S. (1990). Visual perception in people and machines. In A. Blake & T. Troscianko (Eds.), AI and the eye (pp. 21-77). Chichester, U.K.: Wiley.

Ross, P. W. (2001). The location problem for color subjectivism. Consciousness and Cognition, 10, 42-58.

Stark, L. W. & Choi Y. S. (1996). Experimental metaphysics: The scanpath as an epistemological mechanism. In W. H. Zangemeister, H. S. Stiehl, & C. Freska (Eds.), Visual attention and cognition (pp. 3-69). Amsterdam: Elsevier Science B.V.

Stoffregen, T. A. & Bardy, B. G. (2001). On specification and the senses. Behavioral and Brain Sciences, 24.

Thomas, N. J. T. (1998). Zombie killer. In S. R. Hameroff, A. W. Kaszniak, & A. C. Scott (Eds.), Toward a science of consciousness II: The second Tucson discussions and debates (pp. 171-177). Cambridge, MA: MIT Press.

Thomas, N. J. T. (1999). Are theories of imagery theories of imagination? An active perception approach to conscious mental content. Cognitive Science, 23, 207-245.

Thomas, N. J. T. (2001a). Color realism: Toward a solution to the "hard problem". Consciousness and Cognition 10, 140–145.

Thomas, N. J. T. (2001b). Perceptual systems: 5+, one or many? Behavioral and Brain Sciences, 24.

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