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Benjamin Libet: We live 1/2 second in the past and have no free will [View All]

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HamdenRice Donating Member (1000+ posts) Send PM | Profile | Ignore Wed Jul-22-09 06:25 AM
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Benjamin Libet: We live 1/2 second in the past and have no free will
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Edited on Wed Jul-22-09 06:43 AM by HamdenRice
I was just wondering whether anyone else had come across this or pondered the neurophysiological work of Benjamin Libet, and the philosophical questions it raises.

Benjamin Libet did a series of experiments between the 1950s and 1990s that fundamentally challenge our subjective experience of reality and free will.

I won't go into the technical set up of his experiment, which is available on many internet sites. Basically at first, all he was trying to measure was the amount of time it took for a stimulus (say a pin prick on the skin) to be perceived consciously, subjectively by a person. Because of his collaboration with a neurosurgeon and consent of patients he was able to experiment on live human subjects before MRIs were available.

The results were surprising. After gathering data from the late 1950s until the 1970s, he came to the conclusion that it took about 500 msec for a stimulus to be subjectively and consciously perceived by a person. A half second was a surprisingly long time.

In effect, that meant that our conscious selves were "living" one half second later than objective reality. (In recent years, the amount of time has been challenged as much smaller, but in a sense it doesn't matter if the delay is much shorter, because as long as there is a delay, it means our subjective experience of reality and objective material reality were still offset.)

There were several equally disturbing corollaries.

The first dealt with the fact that people experience existence as happening "now". Libet proposed that because we live 1/2 second behind objective reality, our conscious brains then make up a story or illusion, called "subjective referral backwards in time" to make it seem as though our objective material experience of existence and our subjective internal experience of existence were happening at the same time. The experience is "antedated" from reality, in other words.

One essay I've read that discussed the amount of time it takes the conscious brain to parse grammar in conversation made me think of a metaphor for the world Libet described. If you speak a foreign language but are not fluent, when you listen to tv or radio in that foreign language it always feels that you are a half second or so behind, in putting together what the speaker is saying. Libet is saying that reality is like that, except that we then convince ourselves that the delay didn't happen.

Another troubling implication of the delay between objective reality and subjective conscious experience was that it should be impossible to do certain things if this were true. Humans do things much faster than would be allowed with a 500 msec delay. For example, it should be impossible to hit a fastball in baseball. It would be extremely dangerous to drive a car.

The solution to this quandry was solved by a set of even more disturbing experiments. Libet tried to look at the other side of consciousness -- volitional acts. He was able to use very precise markers and time recordings to determine when a person decides to lift a finger, when the various unconscious brain processes (eg motor, "readiness potential") involved in finger lifting began, and when his finger is lifted. (By this time, MRI was available.) The results of this experiment are what Libet is even better known for than the delay experiments or the theory of "subjective referral backwards in time" because they were more disturbing.

Libet found that the unconscious brain processes involved in lifting a finger occurred before the conscious decision to lift a finger occurred. The non-conscious brain prepares to do something before we consciously, subjectively decide to do it. Libet concluded that conscious free will was an illusion. Your unconscious mind is constantly carrying out your behavior, and then your conscious mind tells itself a story that says, "I did that."

This also solved the "subjective referral backwards in time" problem, because the conscious mind "dates" the stimulus at the time that the unconscious mind perceived it.

edited for clarity and italics.
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