Book Review: Consciousness Explained (D. Dennett): part V : Delay of consciousness

In the 80's, Libet reported an experiment where subjects (wearing scalp electrodes) were asked to flex one hand at the wrist while noting the position of a moving spot at the precise time they formed the intention to flex. Afterwards, said subjects reported where the spot was at the moment they decided to flex their hand. The electrical measurements performed by the electrodes permited to determine that the subjects flexed their wrist 350 to 400 ms before the time indicated by the subject as being his time of intention to flex.


This experiment seems to indicate that we are conscious of the decisions made by our brain AFTER they have been made.


It seems to me  that Dennett does not like this conclusion (although he does not express it explicitly) which seems to contradict the intuition that our conscious acts control our bodily motions.

He considers this kind of explanation as being stalinesque (i.e. presuming that the brain delays consciousness in order to be able to presents all the facts it wants to present in the order it wants them to be presented).


He points out that there is an alternative explanation: "the subjects were conscious of their intentions at an earlier moment, but this consciousness was wiped out of memory (or just revised) before they had a chance to recall it". He calls this kind of explanation "Orwellian" because history is re-writen after the facts.

Finally, he also points out that yet another explanation which is that "an element of content becomes conscious at some time t, not by entering some functionally defined and anatomically located system, but by changing state right where it is: by acquiring some property or by having the intensity of one of its properties boosted above some threshold."

Dennett seems to doubt very much the possibility to equal the time of reporting of the subject with the time of conscious experience.


Personally, I would call on Ockham's razor with such an issue: stick to the simplest hypothesis until proven otherwise. Hence, as far as I am concerned, this experiment seems to indicate that consciousness arises after the facts. Clinical cases like the case of Mrs. Dee in "sight unseen" are also pointing toward such an explanation.


I think Dennett doubly dislikes the results of this experiment. 1) as mentioned earlier, it places consciousness after the events and 2) it looks like we are watching a movie of our live in a cartesian theater (he despises the idea of the cartesian theater).


[this page has been amended on 12/03 after a reader pointed to me some errors of interpretation. Thanks to Jason]