Multiple Drafts Model
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Daniel Dennett's Multiple Drafts Theory or Model of Consciousness is a physical theory of consciousness based upon the proposal that the brain acts as an information processor. The Theory is described in depth in the book Consciousness Explained, written by Dennett in 1991. It proposes a form of strong AI.
The theory is unashamedly operationalist, as Dennett says: "There is no reality of conscious experience independent of the effects of various vehicles of content on subsequent action (and hence, of course, on memory)."
Dennett's starting point in the development of the Multiple Drafts theory is a description of the phi illusion. In this experiment two different coloured lights, with an angular separation of a few degrees at the eye, are flashed in succession. If the interval between the flashes is less than a second or so the first light that is flashed appears to move across to the position of the second light. Furthermore the light seems to change colour as it moves across the visual field. A green light will appear to turn red as it seems to move across to the position of a red light. Dennett asks how we could see the light change colour before the second light is observed.
An example of the phi illusion in the format described by Dennett is shown here: phi illusion (http://www.users.globalnet.co.uk/~lka/handle.exe) (use the 'test' option to select the simple phi demonstration).
Dennett explains the change of colour of the light in terms of either Orwellian or Stalinesque hypotheses. In the Orwellian hypothesis the subject develops a narrative about the movement of the lights after the event. In the Stalinesque hypothesis the subject's brain would have a delay in which the movement of the green light towards the red light could be modelled after the sensory information from the red light had been received. He then says that it does not matter which hypothesis applies because: "the Multiple Drafts model goes on to claim that the brain does not bother 'constructing' any representations that go to the trouble of 'filling in' the blanks. That would be a waste of time and (shall we say?) paint. The judgement is already in so we can get on with other tasks!"
According to the Multiple Drafts theory there are a variety of sensory inputs from a given event and also a variety of interpretations of these inputs. The sensory inputs arrive in the brain and are interpreted at different times so a given event can give rise to a succession of discriminations. As soon as each discrimination is accomplished it becomes available for eliciting a behaviour. A wide range of behaviours may occur ranging from reactions to the event such as running away to descriptions of the experience of the event etc.
At different times after the event a person is able to relate different stories of what happened depending upon the extent to which the event has been analysed. Dennett compares this with a 'Cartesian Theatre' model of consciousness in which events suddenly appear on some sort of mental screen and then disappear as quickly. He provides numerous examples to show that events are analysed over a period of time rather than instantaneously.
Although Multiple Drafts is described as a model or theory of consciousness that differs from other models, Dennett points out that even Descartes was aware that reactions to an event could occur over a period of time with reflexes occurring first and judgements later. What makes Multiple Drafts different is that Dennett, in different sections of Consciousness Explained, either denies that normal conscious experiences actually occur or describes these as emerging in some unspecified way from the sheer complexity of information processing in the brain. His emergentism is clear when he defends the Multiple Drafts Model from Searle's chinese room argument by saying of the critics: They just can't imagine how understanding could be a property that emerges from lots of distributed quasi-understanding in a large system (p439).
As an example of denial of conscious experience Dennett denies that there is any internal experience of colour, instead he says that qualia in general are "mechanically accomplished dispositions to react". This view originates in Dennett's belief in the method of heterophenomenology in which narrative is thought to be the most crucial tool for investigating consciouness.
It is the combination of the Multiple Drafts concept with an extreme radical behaviourist point of view that constitutes Dennett's theory of consciousness. What is disappointing about this theory is that it does not explain how complexity makes conscious experience and it denies the existence of any phenomena, such as qualia, that do not comply with the theory. The failure to explain how complexity gives rise to experience means that the theory describes consciousness as a phenomenon that weakly supervenes on an information system and so should probably be classified as a form of dualism or indirect realism with an unknown physical phenomenon that is responsible for consciousness.
See Also
References
Daniel C Dennett. (1991). Consciousness Explained. Little, Brown & Co. USA. Available as a Penguin Book.
Dennett, D. and Kinsbourne, M. (1992) Time and the Observer: the Where and When of Consciousness in the Brain. (1992) Behavioral and Brain Sciences, 15, 183-247, 1992. Reprinted in The Philosopher's Annual, Grim, Mar and Williams, eds., vol. XV-1992, 1994, pp. 23-68; Noel Sheehy and Tony Chapman, eds., Cognitive Science, Vol. I, Elgar, 1995, pp.210-274.http://ase.tufts.edu/cogstud/papers/time&obs.htm
External links
- The Philosophers Magazine: Philosopher of the Month, April 2003: Dan Dennett (http://www.philosophers.co.uk/cafe/phil_apr2003.htm)