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Libet’s “readiness potential” and free will

Brian Leiter

Several readers kindly sent along this article about some new research purporting to undermine Libet's results; of course, objections to Libet's interpretation of his original results are well-known (the article doesn't really convey that accurately it seemed to me).  But I'd be curious to hear from readers familiar with this new research and the philosophical issues what they make of all this.  Feel free to include links to other relevant material.

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4 responses to “Libet’s “readiness potential” and free will”

  1. Ned Block

    This article is right that Schurger's paper reset the discussion of the relation between the readiness potential and the decision to press the button, but its conclusion is philosophically controversial. The key sentence is this one: "The Bereitschaftspotential would be the rising part of the brain fluctuations that tend to coincide with the decisions." As many philosophers have noticed, an alternative interpretation is that the rising part of the brain fluctuations IS the decision.

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  2. Tim O'Connor

    As Ned says, Schurger’s work does call into serious question the role of the readiness potential in the process leading to decision in Libet-style experiments, although the article doesn’t do a very good job of explaining it clearly. The article also fails to convey just how little is presently known about the neural processes underpinning that process. Schurger’s gloss on his findings – that random fluctuations in spiking levels may ‘tip the scales’ when it comes to arbitrary decisions is itself just a (reasonable) conjecture. It’s early in the first quarter, and the game awaits improved technology and techniques. As one of the people involved in the large project mentioned in the article, I am happy to say that the neuroscientists working in this area are eager to collaborate with philosophers in trying to slowly correlate psychological categories with neural structures and processes. Stay tuned.

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  3. Aaron Schurger

    Saying that the rising part of the brain fluctuations IS the decision could be interpreted in different ways. Do you mean that it is the process of coming to a decision, or is it the outcome of a decision? Our account is more consistent with the former. I think that Murakami et al (2014) said it best: Bounded integration models “identify the initial intention to act as the moment of threshold crossing while explaining how antecedent subthreshold neural activity can influence an action without implying a decision.” I don't know how well this view will hold up to a philosopher's scrutiny, but it seems right on the money to me. One point in favor of our account of the RP is that it is parsimonious (relative to the alternative account). The RP is *really* long, on neural time scales, and *really* variable both within and between subjects. If it is the outcome of a decision process, then why should it be so insanely long and variable? On the other hand, if it is antecedent to the decision then it makes sense. (A "decision" here being something like a "neural-level commitment to initiate a given action.")

    Regarding the Atlantic article, I think it is very well written. However, some of the language used is a bit too strong. I would not have used the word "debunk", for example. I'm not sure that we have debunked anything. What we have done is to introduce an alternative and relatively parsimonious explanation, and provided some empirical evidence to back it up. I think that the going interpretation of the RP deserves to be revisited (i.e. called into question) before we use it to draw any conclusions about conscious free will. We may have thrown a wrench into the works, but more research needs to be done before we settle on an interpretation of the RP.

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  4. David Frost

    It seems to me one can say the readiness potential or this or that antecedent correlated brain signature is not whatever others have claimed it to be, as those others attempt to establish that Libet helps skepticism about free will.

    But it would important not to hide in that move denying the significance of the RP, a denial of a broader nature. I think the Libet stuff is interesting but the upshot I take away from Libet is something that we could have arrived at almost non-empirically. Namely, before any conscious decision the contents of the phenomenology of that decision, or just the cause of that decision, will be found in nonconscious parts of the brain. It would have to be. It could not be otherwise. Anything else would suggest a super-Cartesian idea that we are 100% conscious in everything we do, that all mentality is awareness, anything else is biology.

    I mean, we could have known without Libet–indeed from Nietzsche–that the contents of consciousness bubble up from nonconsciousness. Thoughts come unbidden as Nietzsche said. Search this essay of mine for “unbidden” https://www.armchairvertigo.org/p/essay )

    It’s like this: the experimenter gives the stimuli (the instructions) to the participant in the experiment (whether Libet 1.0 or Libet 2.0 or 3.0 with Dylan-Haynes, Soon, and Alexander Huth); and then, as time passes, the participant or subject must decide when to act, when to press the button, which hand, or when to do some math calculation or whatever it is. It cannot be that all the causes relevant to the decision remain at the level of consciousness. Lots takes place unconsciously.

    Indeed if the subject waits too long–or waits like 3 seconds–it is quite possible and almost likely that their conscious experience, their thinking, will go down an unrelated tangent. And, like in meditation, they might have been going along that tangent for a good little while (4 seconds or whatever) before realizing it and remembering that they were supposed to be deciding when to push the button (or in the case of meditation realizing they have not been paying attention to the breath for 4 seconds without realizing it). Whatever tangent they went down was provided by something other than consciousness. It bubbled up. And the really interesting part is people’s phenomenological vocabulary is so meagre and people’s own experience is so mis-described that they might say they went down that tangent consciously or in virtue of a conscious decision (which is not the same thing). But truly paying attention to one’s experience while meditating shows that the tangent came into existence without assisting from consciousness. Consciousness endorsed it immediately but it came out of the darkness of nonconsciousness. You can be down the tangent of thinking about dinner rather than concentrating on your breath, and rather than getting ready to decide when to press Libet-ian buttons… You can be distracted from your task and be conscious of what you are thinking namely “what should I make for dinner” but are you consciousLY proceeding down that tangent. Well you are not MINDFULLY proceeding down that tangent. You started down that tangent because of an unconscious event bringing a thought into consciousness unrelated to your previous conscious state which would have been the breath or preparing to “decide”.

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