Bereitschaftspotential and free will

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Twelfthroot
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Bereitschaftspotential and free will

Postby Twelfthroot » Mon May 28, 2012 8:00 pm UTC

I was recently reading into the notion of Bereitschaftspotential ("readiness potential"), the notion that voluntary muscle movement can be linked to brain activity that precedes the subjective experience of having decided to move. It came up because I've found not a small number of scientists claiming that it somehow clearly invalidates the notion of free will.

To me, this is in no way the case, so I assume I'm either failing to follow their argument or using a different definition of free will, but perhaps it's just a poor interpretation. Consider the following: suppose we hook somebody up to a device to measure their Bereitschaftspotential, such that they can see the readings. For full simplicity: say you're instructed to raise your finger whenever you "want to", and you're wired to a brain scanner such that you can see a light turn on whenever your Bereitschaftspotential is detected.

As far as I can tell, the people applying the experiment as evidence of lack of free will would argue that the monitor would light slightly before every time you raised your finger, and before you felt you had decided to do so. But if that's the case, then you would see the light before you "decide" to raise your finger. From here there are two possibilities -- to me the most likely is that you could then decide not to follow through with moving. This would mean that the monitor did not correctly "predict your action" -- it merely indicated that you were (subconsciously) focusing on or considering raising your finger -- getting bereit. You could use this to claim "impulses to act (or even 'ideas') rise spontaneously from the unconscious mind, without our volition", and I would largely agree. But whether or not we act on these impulses remains unpredictable to others but seems to us entirely within our control -- which to me would be if anything scientific validation of the plausibility of "free will", or at the least definitely not a rejection of it.

The other possibility is that you would see the light but not be able to change your mind "in time", which to me would indeed suggest problems with a notion of self-influencing willpower. But I imagine that the subjective experience of this setup would be indistinguishable from the experience "the light is forcing me to raise my finger", and while this outcome might well force me to reject willfulness, I have a hard time imagining that this outcome is possible. Has this test been carried out? Is it feasible? Unless I'm omitting some other possibility (say, you somehow perceive the light to activate concurrent to your 'deciding' to raise your finger even if another observer would see it preceding your time of decision), this experiment would quite readily either reject the "this says anything about free will" claim or give it serious credence.

I'm sure people have been thinking about this issue more in depth since the advent of the the experiment and the decades-old essays I've been reading. What is the current thinking on this matter?

Slightly tangential clarification:
Spoiler:
Of course, this argument against free will can be extended ad infinitum ("what if we could predict how you would respond to our prediction?"), but it seems to me that in every case the sidestepped contention is "but if you told me that prediction I could invalidate it too" -- i.e. in any case, if one can correctly predict our actions and inform us of the prediction before we feel we have made it, we would either feel that we didn't have free will or feel that the predictor was as a god to us, deciding our decisions for us.

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gmalivuk
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Re: Bereitschaftspotential and free will

Postby gmalivuk » Tue May 29, 2012 8:21 pm UTC

Twelfthroot wrote:For full simplicity: say you're instructed to raise your finger whenever you "want to", and you're wired to a brain scanner such that you can see a light turn on whenever your Bereitschaftspotential is detected.
This is only possible if we first decide what level of potential should get the light to turn on. If instead of a single light you were shown a plot of the potential, I suspect you'd see it start to rise far enough ahead of a finger-raising to be able to change your mind, but that there would be a point of no return beyond which you could not change your mind and not raise your finger after all.

Twelfthroot wrote:you somehow perceive the light to activate concurrent to your 'deciding' to raise your finger
I suspect this is by far the most likely case, if we set the light to go off at or beyond the "point of no return" I described above. It turns out your brain is not particularly good at determining which of two things happened first, especially when they are not even the same sort of thing. (That is, I'd expect you to be able to accurately say which of two lights went on first down to a pretty short time span, but would not do nearly as well if you had to say whether a light went on before or after you felt a tap on your shoulder, and would do even worse if you had to say whether the light went on before or after you decided to move your finger.)
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Twelfthroot
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Re: Bereitschaftspotential and free will

Postby Twelfthroot » Tue May 29, 2012 11:45 pm UTC

gmalivuk wrote:This is only possible if we first decide what level of potential should get the light to turn on. If instead of a single light you were shown a plot of the potential, I suspect you'd see it start to rise far enough ahead of a finger-raising to be able to change your mind, but that there would be a point of no return beyond which you could not change your mind and not raise your finger after all.

Certainly, I agree. However, I don't see this as invalidating free will any more than the similar and irrefutable fact "once you have sent impulses to your finger that will cause it to raise, you cannot decide to not raise it." The way I interpret the experiment, the Bereitschaftspotential is measuring your impulse to raise your finger -- the idea has, without your volition, arisen. But when it arises, it will (or at least can) reach the level of conscious consideration, at which point whether or not it will continue to manifest as action cannot be predicted by anything except the originating entity (be it the brain and/or "the mind") of the action. That is, I only see the Bereitschaftspotential possibly disproving free will if the point of no return always (or almost always) occurs prior to the subjective experience of decision, which I don't think it could.

I don't doubt that our ability to order events, especially of different sensory natures, is easily fooled. But given that the experiment relies on the subjective experience of the participants to determine when they "decided" to move, if I perceive the potential to reach threshold simultaneous with the perception of deciding that I will go through with lifting my finger, I don't see how that can be called mistaken perception.

That said, I'm not sure if you were arguing that the experiment can indeed be used as evidence against free will. If you are, I'd request that you explain how, but given we're talking about free will, I imagine it's very possible that my own definition is too circular to lend any validity to my objections.

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Re: Bereitschaftspotential and free will

Postby gmalivuk » Wed May 30, 2012 3:37 am UTC

Twelfthroot wrote:I don't doubt that our ability to order events, especially of different sensory natures, is easily fooled.
But it's not just that. Our brains are also exceptionally poor at remembering things accurately, and exceptionally good at coming up with after the fact explanations and rationalizations for things. Even if the point of no return precedes the actual awareness of a conscious decision to do something, I doubt it would be accurately remembered as such.
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Re: Bereitschaftspotential and free will

Postby Technical Ben » Wed May 30, 2012 8:22 am UTC

I thought the experiment showed we have a time delay in action/thought processes. Nothing more.
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Re: Bereitschaftspotential and free will

Postby gmalivuk » Wed May 30, 2012 2:08 pm UTC

Which experiment are you talking about? Because the one 12th root and I are discussing hasn't actually been done.
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Re: Bereitschaftspotential and free will

Postby Iceman » Wed May 30, 2012 5:00 pm UTC

Is the whole point just to show you can act before you're aware you're thinking of it?

It really just presupposes that free will must be a result of concious thought, which I wouldn't say is a prerequisite of it at all.

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Re: Bereitschaftspotential and free will

Postby Twelfthroot » Wed May 30, 2012 9:18 pm UTC

Yes, I agree that the experiment which was actually performed simply shows that (to oversimplify slightly) volitions are (detectably) unconscious before they are conscious. However, some scientists (Sam Harris, possibly Jack Copeland) seem to be using this experiment as evidence against free will, so I wanted to see if there was any justification for that claim.

gmalivuk and I were also discussing what kind of hypothetical experiment which could be used for such a claim. On that topic: the experiment relies on "the moment of experiencing having decided" being empirical enough to compare to the moment of detecting potential. Even if you found a point of no return that possibly preceding the "real" moment of decision, I don't see how you could verify that, or give any meaning to the statement "you thought you decided at time X but you are wrong, you decided at X-t". Unless, say, I videotaped myself performing the experiment and with a clock in view from both perspectives, and saw in the videotape that even though I had thought the light activated right when I felt I had decided, but then by examining footage saw that the light consistently preceding the moment I recalled as when I decided, perhaps?

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Re: Bereitschaftspotential and free will

Postby Technical Ben » Thu May 31, 2012 8:36 am UTC

gmalivuk wrote:Which experiment are you talking about? Because the one 12th root and I are discussing hasn't actually been done.


My apologies. There have been tests done AFAIR with scanning brain activity and asking a subject to say when they first think of an action or make a decision. It's been found that there is a delay from the readings in the brain activity to the subject acting on or saying they have had a thought.

Such as this one... http://www.wired.com/science/discoverie ... d_decision Although others might have been done.

"Your decisions are strongly prepared by brain activity. By the time consciousness kicks in, most of the work has already been done," said study co-author John-Dylan Haynes, a Max Planck Institute neuroscientist.

Haynes updated a classic experiment by the late Benjamin Libet, who showed that a brain region involved in coordinating motor activity fired a fraction of a second before test subjects chose to push a button.


Does this mean my concious has no effect on decision making? To mean the answer is no. It may mean it has less immediate effect, but it could still have a big long term effect. Also, for all I know my subconscious could be making the exact same decisions and though processes as my concious. It's just I'm only aware of my concious a few moments after.

In an exam for instance, my subconscious might crunch the numbers and decisions processes, way before my concious kicks in. But it only has the information from what I've fed it by reading a book on mathematics. So then it causes me to write the correct answers to the questions. The fact I only realise I have the answer a few seconds after the though process, does not invalidate the thought process that went into it in the first place.

Hey, most of us have driven a few blocks and not had any "concious" recollection of it. It was still very much a real though process going into that driving. One which we could never have done if our concious decision to "learn how to drive" was never made.
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Re: Bereitschaftspotential and free will

Postby Fire Brns » Fri Jun 01, 2012 6:55 pm UTC

This is highly tangential so feel free to skip by it:

I think a major misunderstanding of free will is that it results in multiple outcomes. Free will I find is self awareness of decisions whereas many simple creatures only respond to stimulus we are constantly creating new information on our own. Let's say you are deciding what you want to eat for lunch, ham n cheese or PB&J, you ultimately make a decision but there isn't a universe where you eat ham n cheese and a universe where you eat PB&J. You made a choice, if every option was selected that would undermine free will as no choice was truly made.
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Re: Bereitschaftspotential and free will

Postby fr00t » Fri Jun 01, 2012 8:39 pm UTC

It would be an interesting experiment, but not because of what it would tell us about free will (one way or the other). From what I recall, there was a pretty significant amount of time between readiness potential and the action itself, like on the order of a second. I lost the book but I seem to also remember further evidence for our brain buffers the sensory feeds so there is a short latency, but then does some post-editing to give us the illusion that our consciousness is in charge.

Iceman wrote:It really just presupposes that free will must be a result of concious thought, which I wouldn't say is a prerequisite of it at all.


I think that sums it up. We understand our minds and the phenomena of consciousness so poorly, we don't even know how to ask the right questions. Armchair philosophizing about free will at our level of neuroscience is probably as effective as astronomers were without telescopes.

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Re: Bereitschaftspotential and free will

Postby Rhadamanthys » Mon Jun 04, 2012 8:17 pm UTC

From what I recall, the point Harris makes while citing said experiment is that if indeed the "decision" to raise your finger isn't made consciously (i.e. the moment you feel, as an agent, that you choose to do so) but rather seconds before through an inscrutable process you're not aware of, then you did not choose to raise your finger any more than you "choose" to produce red blood cells or make your heart beat. In other words, you merely witness the result of a process over which you have no control in any meaningful sense of the word.

Regarding the experiment proposed by the OP (test subject sees Bereitschaftspotential-detecting-light switch on, decides not to raise finger), I would say — intuitively and without any scientific basis to back this up — that there are three possible outcomes:

1) The test subject knows that the light will switch on whenever the Bereitschaftspotential to raise his or her finger arises, and decides in advance that he or she will prove the machine wrong and never raise it. But in doing so, the test subject is actually never "bereit" to raise his or her finger and thus never allows the light to switch on in the first place.

2) The test subject hasn't yet decided what he or she will do upon seeing the light switch on, and when it does either:
a) decides to raise his or her finger as predicted and does so, while the light accordingly stays on; or
b) decides to prove the machine wrong and keeps his or her finger down, while the light accordingly switches off (and indeed some fraction of time before the test subject becomes conscious of the decision to prove the machine wrong).

For this to make sense, one has to understand the machine not as something meant to predict your future actions, but rather your readiness to do an action given the perceived circumstances (i.e. the decision your brain makes given some input; a decision you become aware of seconds later). As soon as the circumstances change (the light switches on), your brain is faced with a new situation and the Bereitschaftspotential may vary — while you still become aware of the decision only moments later, as per the intial premise.

This is of course, as another poster has pointed out, highly speculative. The conclusion that Harris draws still seems pretty unavoidable, IMHO.


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