The Libet free will experiment revisited

I have long been interested in the question of free will and back in 2010 even wrote a 16-part series (!) looking into what was known about it. Many people are Cartesian dualists where they view the brain and mind as distinct, the former being a physical organ while the latter is an immaterial entity, dubbed the ‘Ghost in the Machine’ by Gilbert Ryle, that controls the cognitive processes of the former, though how that actually happens has not been made clear.

Back in 1983, Benjamin Libet used a technique to measure brain activity that was called Bereitschaftspotential (readiness potential) that had been discovered nearly twenty years earlier by two German scientists Hans Helmut Kornhuber and Lüder Deecke who concluded that there was brain activity prior to the decision to tap one’s finger. Libet did more measurements and found that the brain activity started about 500 milliseconds before the action but that the participants were conscious of making a decision only 150 milliseconds before the action. This seemed to suggest that the action was decided upon 350 milliseconds before the person became conscious of making it, throwing the idea of free will into serious doubt. (You can read more about Libet’s experiments here.)

A new experiment has revisited Libet’s experiment and has suggested an alternative explanation, that the brain has random rises and falls of the readiness potential and that the correlation between that activity and the decision to act may not be a strictly causal one.

In a new study under review for publication in the Proceedings of the National Academy of Sciences, Schurger and two Princeton researchers repeated a version of Libet’s experiment. To avoid unintentionally cherry-picking brain noise, they included a control condition in which people didn’t move at all. An artificial-intelligence classifier allowed them to find at what point brain activity in the two conditions diverged. If Libet was right, that should have happened at 500 milliseconds before the movement. But the algorithm couldn’t tell any difference until about only 150 milliseconds before the movement, the time people reported making decisions in Libet’s original experiment.

In other words, people’s subjective experience of a decision—what Libet’s study seemed to suggest was just an illusion—appeared to match the actual moment their brains showed them making a decision.

The issue of whether we have free will is far from settled because there are still other studies that suggest that we do not.

There is a lot riding on this question because not only does the question of whether we have free will have moral, ethical, and legal implications, there is something deeply unsettling in the idea that we do not have free will, thus losing our sense of agency, and that we are not responsible for our actions. People tend to desperately want to hold on to the idea that they consciously control their decisions. As Isaac Beshevis Singer said, “We must believe in free will, we have no choice.”

Where does a lack of free will leave the idea of culpability and the insanity defense in criminal cases? Anthony Cashmore takes a close look at that question.

Here is a video discussing the implications of brain science and the lack of free will for the law.


  1. anat says

    The whole concept of ‘free will’ comes from earlier times in the understanding of the human mind and is based on assumptions that are intuitive, but have to be questioned once one accepts that our sense of self does not mean the self is a well-defined entity with clear boundaries, isolated from our bodies and the rest of the physical universe. We know that the choices we make are influenced by the state of our body (including the brain), but then, anything we are exposed to changes the state of our brain at least somewhat.

    The best way forward, IMO, is to get rid of the concept of culpability (and with it the concept of punishment), and focus instead on what means are likely to result in better behavior in the future for each individual case. And if the evidence suggests that a certain person is likely to behave in ways that are unacceptably harmful to others with little chance of improvement then long-term confinement is needed.

  2. Ketil Tveiten says

    “Free will” is like most of the old philosophical canards in that it is an undefined concept, and perhaps even an undefinable concept. Trying to reason about such things will inevitably get you nowhere, unless you’re really really careful about it -- which basically no one is.

    Further reading for the interested: “what does ‘free will’ even mean?” is the central question Daniel Dennett worked on, try his essay The varieties of free will worth wanting for a starter.

  3. says

    Neural activity doesn’t mean we have free will; it just means that something is causing neural activity before we recognize that we have made a decision.

    I think we’d need to have an agreed-upon definition of what constitutes free will before we can say what kind of action we’d have to measure, and when, that would indicate we had it. Personally I am unconvinced that it’s a topic that’s worth discussing. [I then go on to discuss it, but I can’t help myself because I have no free will]

    Researcher: “OK, now when I turn the scanner on, I want you to raise a finger. OK? GO!”
    Subject: (raises finger)
    Researcher: “See!? You have free will!”
    Subject: “but I was doing what you told me to do.”

  4. Dauphni says

    Speaking as someone who dissociates a lot, I can say from experience that the control I have over my decisions is a very very variable thing.
    Even without such fairly extreme experiences, I think most people can recognise times when their decisions are controlled not by their rational thoughts, but by impulses originating elsewhere in the body.
    Of course a common objection to that is that we as humans should be able to override that through sheer force of will, but as any addict can tell you, that’s just not how it works.

  5. starfleetdudet00 says

    Dennett’s work “Freedom Evolves” (2003) already anticipated this news about Libet’s experiment not being conclusive.

  6. says

    Of course a common objection to that is that we as humans should be able to override that through sheer force of will, but as any addict can tell you, that’s just not how it works.

    Anyone who has accidentally grabbed an electric fence also knows that.

  7. mnb0 says

    “there is something deeply unsettling in the idea that we do not have free will”
    And what would that “something”be? While my bet is that free will is a useful concept on naturalism/ materialism (note: I tend to lose such bets) I don’t see what is supposed to be unsettling. Free will or not, it’s a scientific given that many of my views and manners have been influenced by lots of people.
    The big problem with free will is that it never has been properly defined. Many christians and many unbelievers seem to think that free will only can have meaning on dualism (“while the latter is an immaterial entity”). As they never show why free will can’t be defined on naturalism/ materialism the result is a false dilemma.
    That alone is enough reason for me to bet on free will. From one of your links:

    “Note that the predictions of which button to push were not perfect, with only
    around 60% accuracy.”
    That’s hardly impressive as soon as you realize that the default position is 50%. It’s easy to understand that 0% would be a strong argument to reject free will.
    Now several years ago I read that the highest score is 75%. If this isn’t raised considerably, say to 95% (note that physicists raise the bar considerably, to well over 99%, when talking about elementary particles), there is lots of room for a naturalistic definition for free will.

    From the other link: “granting for the sake of argument that the idea of a god who can read everyone’s thoughts makes any sense at all.”
    No way I’m going to grant this.

    “Libet argues that secular ethical systems will also have to adjust”
    As a utilitarian the only adjustments I’m going to accept are those who work in terms of lowering crime rates. As a result the discussion on free will has very little impact on “moral, ethical and legal implications” asaIc.

    “Where does a lack of free will leave the idea of culpability and the insanity defense in criminal cases?”
    In the latter case Dutch law has something called “terbeschikkingstelling”.

    This means mandatory treatment in psychiatric clinics like the Mesdag clinic in Groningen. It’s possible that this treatment is lifelong.
    As for the idea of culpability there is this imaginary conversation:

    Criminal: Your honor, you can’t hold me responsible for my decisions and actions and hence should not punish me. Scientific consensus is that people don’t have free will.
    Judge: Neither do I have free will and I can’t do anything but sending you to jail for five years. Next case.

    The discussion is far less relevant as way too many people think. Perhaps this is why I don’t see how it’s unsettling.

  8. anat says

    Dauphni @4:

    Even without such fairly extreme experiences, I think most people can recognise times when their decisions are controlled not by their rational thoughts, but by impulses originating elsewhere in the body.

    That’s one of the points of disagreement I have with my husband. He considers such impulses as part of ‘free will’ -- ie he considers the subconscious processes in the brain as part of the same self that is making choices, regardless of whether the narrating self is aware of them or not, whereas I think all our choices are probably caused by things that ultimately lie outside of ourselves and we just come up with an after-the-fact narrative to convince ourselves why we did what.

  9. Jean says

    Do chemical processes have free will? The brain is just a very complex arrangement of molecules affected by an uncountable numbers of inputs (past and present) affecting chemical processes. The actions are the result of these chemical processes so they will be what they will be regardless of the illusion of free will we have.

  10. Lassi Hippeläinen says

    So there’s a fork in the path, and you can choose right or left. Is that free will? The purist says no, because you are forced to stay on the path. The minimalist says yes, because there is still one bit of choice left.

    A fairly recent book (from 2015) that explores the various approaches and suggested solution is “Freedom Regained: The Possibility of Free Will” by Julian Baggini. His conclusion is that there is room for free will -- as you can guess from the title.
    The first chapter is a bit slow, but from there on it gets on the move.

  11. starfleetdudet00 says

    I’ve always thought the strict determinist take on free will amounts to no more than hindsight being 20/20. Sure, after something happens, then we can say with utter confidence that it was going to happen. Get back to me when your determinism can do more heavy lifting than that with respect to free will. Otherwise, there’s no good reason to deny that there is some degree of freedom that humans and other sapient beings possess.

  12. file thirteen says

    In the future there may be artificial intelligences which surpass human thought in every respect. And yet as programmed entities, they will have as much free will as a landslide does. All but the ignorant will know they won’t have free will, but if it weren’t known to be fact, facing them, would we believe it?

    And if they hold arguments on the same subjects with different people or groups of people, they may come to different conclusions. That’s because their behaviour is not merely a function of their own programming (minds and bodies for us) but also of their inputs, which are functions of everything that happens everywhere, and of their memories, which are functions of previous inputs, ie. of everything that has happened.

    Faced with these artificial gods, it will be harder to support the idea of free will. I don’t see living creatures as any different to machines myself. But as mnb0 says, this revelation may be less important than people fear. I am what I am; I do what I do; I think what I think. So what? I’m too complex to be predictable; my mind will, and does, change, from moment to moment.

    There will still be culpability and redemption.

    (the only spanner in the works is the question that forever bugs me; why am “I”, this observer, experiencing this consciousness? But I don’t believe that can be tied to the question of free will)

  13. anat says

    starfleetdudetoo @11:

    If the reason for non-determinism is a random process, where is freedom? How is that a meaningful source of accountability? It is not enough to disprove determinism to show that free will (however defined) exists, and actually plenty of proponents of free will say their version of free will is compatible with a deterministic universe, or even require the universe to be deterministic to work. So your comment is neither here nor there.

  14. says

    “Free will” is like quantum mechanics, in that it is impossible to predict outcomes on an individual basis but it gets easier as the number of particles (people) increases.

  15. Ridana says

    I’ve always been skeptical of that experiment because of the self-reporting aspect and the times involved being in milliseconds. I’m not even sure how I’d go about simultaneously deciding to move my finger while noting the time at which I decided that. Just the act of noting the time would itself delay my action. So it seems reasonable that I could actually, consciously, decide to move less than half a second before I note the time, and then after completing that task would able to move.
    I’m not thinking very clearly at the moment, so if that makes no sense, my point is that I can’t believe in this experiment until they figure out a way to objectively determine the point of conscious decision making. I’m not even sure that’s possible unless someone develops mind-reading technology. But self-reporting is too subjective and itself influences the outcome.

  16. Jenora Feuer says

    While Persinger is problematic for multiple reasons, I did kind of like his approach to this question. Basically, what we consider ‘consciousness’ is actually the result of the serialization of the parallel processing going on in the brain. Consciousness isn’t actually our mind happening, it’s the part where our mind tries to understand itself, after the fact. The actual decision being made comes before the conscious recognition of the decision.

    ‘Rational’ decisions are ones where the serialization catches multiple stages of the decision-making so we can backtrack and check it all; ‘Intuitive’ decisions are ones where all the decision-making happens in a part of the brain that doesn’t get serialized regularly so the idea just seems to come from nowhere to the consciousness-tracking.

    This doesn’t really answer whether we have ‘free will’ or not, since that is such a vague question as to be almost unanswerable anyway. It does suggest that a lot of the people looking for ‘free will’ are looking at the wrong thing, because consciousness happens later in the process than the timing they’re looking at.

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