Biology of Will - Libet's experiment

[selfAdjoint]

Here is a discussion of a recent experiment paralleling Libet's famous one of 20 years ago. Our free will is "spread out" (Dennet) in time.

http://www.carlzimmer.com/blog/C1015037710/E317172943/index.html

 

[Mentat]

So, what kind of insights do you think we can glean from this experiment? What did Dennett use it for (I can't remember his application, though I do remember him explaining the experiment, for some reason)?

 

[Monique]

The application? Proving that free does not exist and that we don't become aware of our intentions until we are already doing them.

I am not sure about the experiment though, in the article they say: "In other words, they had already started preparing to make a voluntary movement for half a second before they felt like they were making a voluntary movement."

How is this half a second determined?

 

[Monique]

The time between the EEG peak and the actual button push? And since subjects were able to push the button within milliseconds of the correct timing position, this would be the positive control?

I am not sure about the purpose of the parietal patients.. (never really heard of the experiment in general before).

 

[selfAdjoint]

It's quite famous in consciusness circles. You sit and watch a clock hand go around, much faster than a second hand. You also have your eye on a light by a button, which you keep your finger lightly on. Plus, your hooked up to an EEG rig (this was 20 years ago).

So the light goes on and you push the button as quickly as possible while memorizing the position of the clock hand. Then you write down the mark the hand was by when you decided to push the button. Many subjects were tested and the EEG rigs found the attention spike occurred about an average of 1.5 seconds before the time the subjects noted down. So our body's (brain's) response comes measurably before our conscious response.

Some people say this contradicts free will, since by the time we get a chance to make a decision the action is already in progress. Dennet takes a broader view. He retains a kind of ghost of free will, spread out over that 1.5 seconds and partly subconscious.

 

[Monique]

Who says there is not a delay in reading the clock? I can imagine it takes time to process the position the arm is in and to translate that to a time to be written down.

How about the example of sitting in a car, driving along. All of a sudden the car in front of you slams the break. Will you break immediately upon seeing the red lights?

The answer is no! It is very well known that it takes time to process the signal and take action, this would argue against the timing experiment right?