Bridgeman's effort to say something new or useful about consciousness and language is flawed. His major theoretical construct, the "plan," on which he depends to develop his arguments is defined in at least four different ways. Consciousness, which is variously described as the operation of the plan-executing mechanism or the outcome of its operation, is relegated to a purely epiphenomenal status with no psychological functions ascribed to it. Finally, Bridgeman's discussion of perception as deriving from the "plan-monitoring mechanism" leaves much that is known about perception unaccounted for.
1.2 Bridgeman's title offers a grand promise but unfortunately what follows is programmatic, at best. Nothing new is presented. He uses terms like "consciousness," "plans," and "goals," in an ill-defined way without offering operational definitions for them. His arguments are sometimes self-contradictory, frequently unsupported by evidence, or by reference to the growing scientific literature on consciousness (Baars, 1988, in press; Baars & Newman in press; Crick 1984; Mandler 1975; Marcel 1983; Marcel & Bisiach 1988; Posner & Rothbart 1992; Milner & Rugg 1992; Shallice 1988; Weiskrantz 1986).
1.3 There are at least three major problems with the target article. First, Bridgeman's definition of the notion of "plan" is not clear or consistent and does not address everyday experience or empirical data. Second, his view seems to be that consciousness is epiphenomenal -- it apparently has no function. Third, Bridgeman seems to advance a simplistic motor theory of perception- -- a notion that has been offered previously elsewhere.
1.3 Looking more closely, we can see that Bridgeman's definition of plan is not entirely clear. Consider: A plan is "an internally held image of an intended achievement" (2.2). "The plan is defined... to mean a scheme that can control a sequence of actions to achieve a goal" (2.2). "It is plans that motivate behavior" (2.3). "The plan becomes the path from motivation to action" (2.6).
1.5 According to Bridgeman's definition, then, a plan is an unconscious entity that incorporates motivation, image of the goal, and a series of steps to achieve the goal. At this point we should note that the same goal can generally be accomplished in more than one way. To take Bridgeman's example, a goal to examine an object could be accomplished by walking over and picking it up, sitting where you are and squinting at it, putting on your glasses, or asking someone to bring the object to you. Thus, in Bridgeman's scheme a single goal could be achieved by executing several plans. How do we decide which plan will be used if consciousness does not arise until execution is undertaken? Do we decide unconsciously?
1.6 The most serious problem in Bridgeman's proposal is that "consciousness is ...nothing more or less than a result of the operation of [the plan-executing mechanism]" (2.8). The architecture of the plan-executing mechanism is not further specified, though in 2.7 Bridgeman alludes in a general way to "neurological machinery" that "must" exist. Throughout the discussion, Bridgeman takes this "nothing but" attitude toward consciousness. Thus, in 2.9, "consciousness has no separate existence of its own. Because it is an effect, not a cause, there is no sense in looking for its functions." In fact, consciousness seems to be in the way theoretically -- being something that must be explained but that itself has no explanatory power. Nowhere does Bridgeman carry out the kind of contrastive analysis that has been so useful in teasing apart the varied functions of consciousness (Baars 1988). For example, what can be learned from noticing the difference between the extensive conscious concentration required for performance of an unskilled act and the relatively fleeting consciousness required during the execution of THE SAME ACT when it is, with practice, performed skillfully? Consciousness per se seems to serve no function in Bridgeman's analysis and hangs around like an epiphenomenal appendix.
1.7 According to 4.6, "we become aware only of the plan currently being executed and of the perceptual and motor events surrounding it." Apparently, once an unconscious decision is made about which plan to execute, we become conscious of its perceptual and motor consequences. This contradicts everyday experience. It seems more accurate to say that we are conscious of the decision "to do x" or "to say y" but we are not conscious of the articulatory processes or the detail control of further action. For example, having reached a decision to "say hello," we are not aware of the detailed movements of our vocal tracts during the course of the production. This is true even though speech is clearly the most complex and rapidly executed motor system available to human beings. Many students of motor systems believe that the only conscious components of complex skills, like speech production, are PERCEPTUAL feedback loops (Levelt 1989)!
1.8 Bridgeman's account of perceptual mechanisms is similarly flawed -- which is surprising for someone who has made a career of very sophisticated studies of perception. The account basically comes down to a motor theory of perception, an idea that has a substantial history in speech perception (Studdert-Kennedy, Liberman, Harris & Cooper 1970;) and cognition (Weimer 1977). In Bridgeman's terms (3.3), "speech understanding is handled by another existing module. It normally monitors the progress of plans, taking the sequence of events and packing it into an idea." Thus the only way we get perception is by reference to plans. The trouble is that this motor theory of conscious perception seems to have no place for stimulus input as such, independently of plans. But our plans are very often interrupted by events for which we have no plans yet which are nevertheless conscious. The long research tradition on the orienting response makes the attention-grabbing effect of unexpected stimuli quite clear (Sokolov, 1963).
2.1 Bridgeman's effort to say something new or useful about consciousness and language is flawed. His major theoretical construct, the "plan," on which he depends to develop his arguments is defined in at least four different ways. Consciousness, which is variously described as the operation of the plan-executing mechanism or the outcome of its operation, is relegated to a purely epiphenomenal status with no psychological functions ascribed to it. Finally, Bridgeman's discussion of perception as deriving from the "plan-monitoring mechanism" leaves much that is known about perception unaccounted for. We find these shortcomings especially surprising in the face of the burgeoning empirical and theoretical literature on consciousness.
Baars, B. (1988) A cognitive theory of consciousness. New York: Cambridge University Press.
Baars, B. (in press) A global workspace theory of consciousness. In A. Revonsuo and M. Kamppinen (Eds.), Consciousness in philosophy and cognitive neuroscience, London: Routledge.
Baars, B., and Newman, J. (in press) A neurobiological interpretation of the global workspace theory of consciousness. In A. Revonsuo and M. Kamppinen (Eds.), Consciousness in philosophy and cognitive neuroscience, London: Routledge.
Bridgeman, Bruce (1992a) On the Evolution of Consciousness and Language. PSYCOLOQUY 3(15) consciousness.1
Crick, F.H.C. (1984) Function of the thalamic reticular complex: The searchlight hypothesis. Proceedings of the U.S. National Academy of Sciences 81: 4586-93.
Levelt, W. J.M. (1989) Speaking: From intention to articulation. Cambridge, MA.: MIT Press.
Mandler, G. (1975) Consciousness: Respectable, useful, and probably necessary. In R. Solso (Ed.), Information processing and cognition: The Loyola Symposium, Hillsdale, N.J.: Erlbaum.
Marcel, A. J. (1983) Conscious and unconscious perceptions: An approach to the relations between phenomenal experience and perceptual processes. Cognitive Psychology 15: 197-237.
Marcel, A.J. and Bisiach, E. (Eds.) (1988) Consciousness in contemporary science. Oxford, U.K.: Oxford University Press.
Milner, A.D. and Rugg, M.D. (Eds.) (1992) The neuropsychology of consciousness. London: Academic Press.
Posner, M.I. and Rothbart, M. K. (1992) Attentional mechanisms and conscious experience. In Milner, A.D. and Rugg, M.D. (Eds.) (1992) The neuropsychology of consciousness. London: Academic Press.
Shallice, T. (1988) From neuropsychology to mental structure. Cambridge, UK.: Cambridge University Press.
Sokolov, Y.N. (1963) Perception and the conditioned reflex. New York: MacMillan.
Studdert-Kennedy, M., Liberman, A.M., Harris, K.S., and Cooper, F.S. (1970) Motor theory of speech perception: A reply to Lane's critical review. Psychological Review 77: 234-249.
Weimer, W.B. (1977) A conceptual framework for cognitive psychology: Motor theories of mind. In R. Shaw and J. Bransford (Eds.), Perceiving, Acting, and Knowing: Toward an Ecological Psychology. Hillsdale, N.J.: Erlbaum.
Weiskrantz, L. (1986) Blindsight. Oxford: Oxford University Press.