Home > Determinism, Philosophy, Philosophy of Mind > Libet Revisited: Neuroscience, Intentions, and Free Will

Libet Revisited: Neuroscience, Intentions, and Free Will

February 24, 2011 Leave a comment Go to comments

**Note: The content of this post has been edited and expanded since the original posting. Additionally, a version of this post can be found here at UNFSPB.**

In “Agent Causation” Timothy O’Connor makes a passing assertion that there are many unresolved questions for materialist agency as he posits it, and that many of these questions are empirical in nature and can only be resolved with “extensive advancements within neurobiological science.” [1] Two particularly salient questions are (1) “Precisely to what extent is an ordinary human’s behavior directly regulated by the agent himself, and to what extent is it controlled by microdeterministic processes?”[2] And (2) whether microdeterministic processes can be predicted or not. While O’Connor may believe that advances in neuroscience will reinforce rather than call into question his theory, this is not the case. Stretching from the 1980s to a recent study in 2008, neuroscience has demonstrated that predictive brain activity can be seen to occur prior to a test subject’s consciousness of making a decision. From Libet to present, these studies provide damaging replies to the questions which O’Connor’s theory leaves unanswered.

In 1985, Benjamin Libet crafted an experiment to measure what he deemed “unconscious readiness potential” (RP) and a test subject’s experience of having an intention or volition toward a specific, repetitive movement at chosen intervals. Libet measures Readiness Potential as voltage levels in the brain. Paling in comparison to today’s standards of FMRI machines and 3 dimensional mapping, Readiness Potential simply indicated an increase, decrease, or maintenance of brain activity as measured by changes in voltage. The original test was set up where brain activity was monitored as the subject performed the task, which allowed Libet to measure the interval between the beginning of brain activity, the claim of conscious feelings of volition, and the action being performed. The tests demonstrated a marked and measurable increase in brain activity prior to the subject reporting becoming conscious of deciding to flex his or her wrist. On average, 200ms elapsed between the subject becoming aware of willing the action and that action taking place.  However, a change in the subject’s RP occurred 550ms prior to the actual flexing of the wrist. This meant that, on average, 350ms elapsed between increased RP in the motor cortex and the subject becoming aware of willing the action. In effect, measurable brain activity was occurring prior to the subject’s consciousness. Libet’s reading of these results was that, should it be the case that we choose to act out of consciousness, there would not be a 350ms period of activity prior to the subject becoming aware of the intention to act.[3] This would seemingly point to the conclusion that brain activity prior to consciousness, not conscious decision-making, was the cause of a subject’s action. At the very least, it would seem that such antecedent brain activity must be explained.

Adding a layer of complexity to Libet’s study were instances of ‘veto’ where subjects were capable of changing their decision to flex their wrists at the last moment, reporting that this occurred in the last 150ms of the experiment. Libet indicated it was this narrow margin which seemed to give hope that human action could indeed be caused, or at least effected by, conscious choice.[4] Discussing the case of veto scenarios, Libet writes that “The concept of conscious veto or blockade of the motor performance of certain intentions to act is in general accord with certain … views of ethical behaviour…‘Self control’ of the acting out of one’s intentions is commonly advocated.”[5] Such vetoes, however, are hardly the substantial platform upon which free will might rest that Libet believed them to be. As John Ostrowick points out in “The Time Experiments of Libet and Grey Walter,” it would seem that veto scenarios only offer a negative definition of freedom – the ability to stop oneself from acting rather than be the source of one’s actions. This, of course, is presupposing that veto decisions do not themselves possess unconscious antecedent brain activity.[6] In The Actor’s Brain, Sean Spence also argues that we would have good reason for postulating that all conscious vetoes are preceded by unconscious brain activity and that the act of consciously vetoing is merely a construct after the fact.[7]

Since Libet does not seem to offer any substantial reason as to why vetoes do not have similar antecedents, or is vague in that if antecedents exist they are unconscious, we are still left without a positive account of conscious deliberation or choice playing a causal role in action a la O’Connor’s defense of indeterministic reasons explanation.[8] I need not offer a detailed account for why O’Connor and other agency theorists must be committed to the claim that deliberation, consciousness, or reasons play some role in free action – this is because the agent’s ability to participate in action is an implicit requirement of any ‘interesting’ definition of freedom. For if reasons, deliberation, or consciousness play no role in action, then in what meaningful sense can the agent participate in her own actions? Alternately, if the cause of action is unconscious brain activity, conscious deliberations seems to have been preceded, and therefore superseded as a cause, by brain activity outside the control of the agent.

However, the details and science of Libet’s studies do leave room for error, as well as questions about the equipment utilized, etc. The margin of error for Libet’s experiment is quite small, measured in milliseconds, making it difficult to ascertain whether the margin of error was to blame for the conclusion that brain activity geared toward action occurs prior to a person choosing to act. Similarly, because RP measurements only demonstrate an increase in voltage in the brain, an argument could be made that such antecedent unconscious brain activity is merely preparing the agent’s brain for deliberation, choice, or conscious action. Recently, however, a new study has emerged that confirms Libet’s findings and provides substantial evidence that brain activity precedes conscious volition by a much larger degree than in Libet’s experiment and that this very same brain activity can be utilized to predict between two choices what choice the subject will choose with a significant level of accuracy.

Published in Nature Neuroscience, “Unconscious Determinants of Free Decision in the Human Brain” found that “the outcome of a decision can be encoded in brain activity of prefrontal and parietal cortex up to 10s before it enters awareness.”[9] Chun Siong Soon and the other authors of the study postulate that the delay between brain activity and the subject’s awareness is due the communication among high-level control centers preparing for action. This study made use of fMRI that monitored the subject as she viewed a series of letters on a screen. When the subject felt the desire, she pressed a button in either the left hand or right hand. After pressing the button of her choice, the subject then was presented with a selection of letters and asked which letter was being displayed on the screen when she felt the desire to press a specific button. In order to clarify the testing procedure, Figure 1 from the study is represented below.[10]

Figure 1

This study clearly surpasses Libet’s experiment in a number of ways. First, the technology utilized far surpasses the EEGs and oscilloscope used by Libet in its ability to record information but also in its ability to differentiate areas of the brain. For example, Libet tested only the motor cortex. This most recent study was able to simultaneously monitor 7 different areas of the brain and measure each area’s separate predictive capability. Secondly, as mentioned earlier, this study turned the several hundred millisecond interval between brain activity and consciousness into a 7-10 second interval, thanks in part to advances in technology. Thirdly, the ability to utilize brain activity to predict what choice the subject will take anywhere from 7-10 seconds prior to the subject even having the experience of deciding to choose:

Taken together, two specific regions in the frontal and parietal cortex of the human brain had considerable information that predicted the outcome of a motor decision the subject had not yet consciously made. This suggests that when the subject’s decision reached awareness it had been influenced by unconscious brain activity for up to 10 s, which also provides a potential cortical origin for unconscious changes in skin conductance preceding risky decisions.[11]

The predictive capability of this study is where, in my opinion, true ground has been gained toward demonstrating physicalist reduction claims. The Soon study demonstrates that the frontopolar and precuneus regions of the brain demonstrate the highest predictive capability prior to conscious decision, hovering around 59-60%. There is also a noted difference in predictive capacity between brain areas both before and after conscious decision. So, prior to the conscious decision the frontopolar and precuneus regions have a 60% predictive capacity and the motor cortices have predictive capacities at or below 50%. After the conscious decision, however, the cortices display a predictive capacity around 62% and the frontopolar and precuneus regions show diminished capacity at round 54%.[12] Even though Libet’s original experiment entailed the possibility that brain states might determine a specific action, the lack of predictability (paired with his margin of error), meant that his findings could be shrugged off as inconclusive, or just seen as proof that brain activity prepares a person to make a decision but does not determine which decision a person makes.

With the discovery of predictability comes the stronger argument that brain activity does not merely prepare for some sort of agent causal power but rather determines such behavior, all the while unbeknownst to the agent. As the Soon study says, “Also, in contrast with most previous studies, the preparatory time period reveals that this prior activity is not an unspecific preparation of a response. Instead, it specifically encodes how a subject is going to decide.”[13] However, there are two potential criticisms that might threaten physicalist conclusions, and represent potential replies from those who adopt O’Connor’s theory of agent causation, or those who may be skeptical of these conclusions.

Potential Criticisms

The first of these potential criticisms is that brain activity might encode meaningless choices, like when to press a button (and which button to press) or when to wiggle a finger. However, there is no guarantee that complex, weighty actions are similarly encoded. A choice between left and right carries no importance to an agent, whereas the choices that interest agency theorists and determinists alike are those that carry the most significance, such as choices for which agents may be held morally responsible.

It is true that the structure of the Soon test does not allow for measuring non-choices (i.e. choosing not to press either button) any more than it allows for complex, weighty decisions. Despite this, there is a sense in which a correlation can be drawn between planning  and ‘weighty’ or ‘moral decisions, and between spontaneity and  ‘meaningless’ choices.  Indeed, Libet found there was a measurable difference in RP between those subjects who planned or considered their actions versus those who acted whenever they felt the desire. In subjects who allowed time for ‘planning’ before an action, the RP occurred earlier and increased at a slower rate than  in subjects who acted spontaneously, when RP occurred much later and the rate of increase was much sharper.[14] This is confirmed by a later study, published in 2006, which found late and early components of the RP. The ‘early RP’ seemed to increase in instances where “the agent attends to their intention, is learning a new task, or uses greater physical force.”[15] In contrast to this is ‘late RP’ which increased when actions required precision or strict, isolated muscle use, leading to the conclusion that ‘late RP’ was involved with fine tuning action.[16] Because there is a marked and measurable difference between planned versus spontaneous action, it is not unreasonable to draw a parallel between planned action and ‘weighty’ action. This is because it must surely be the case that planning involves the weighing and measuring of the different options open to a person. So, the content of the action itself would seem to be far less important than whether or not any planning occurred. Because antecedent brain activity was detected in the cases of those who planned as well as those who did not, it seems warranted to conclude that more complex or ‘weighty’ decisions that require more planning would still possess antecedent determined brain activity.

The second potential criticism is that the margin of error could be greater than anticipated because the study relies upon the person’s subjective memory of when they felt they became conscious of beginning to decide. The person could be mistaken, or the apparatus for indicating when the experience of volition occurred could be unrefined.

While this is a possibility, especially with Libet’s older experiments, the most cutting edge and recent experiments would seem to negate such a response. This is because even if it is granted that there is an additional 2 seconds in the margin of error to account for the subject not being sure when s/he decided to choose, there is still a wide enough interval to demonstrate that brain activity occurred prior to the subject becoming conscious of deciding, and that this brain activity can predict fairly accurately the exact choice that will be made. Also, we can postulate that because the Soon test improves upon the Libet experiment and also confirms its findings, similar future studies would also confirm these findings and improve upon the margin of error and possibly the interval, predictability, etc. Equally, because the experiments are testing the timing of volition and action, and we currently do not have a way to observe volition outside of deciding when and where RP factors into volition and consciousness, there is a sense in which these experiments are necessarily subjective.

While the Soon and Libet studies are surely not a knockdown argument against agent causal theorists, I believe they present a significant hurdle to overcome if one is to propose that brain activity does not determine or predict the actions of an agent. They present an equally high hurdle for agent causal theorists who wish to claim that consciousness can inform action without being determined by antecedent physical properties, i.e. neural properties. While not complete and certainly improvable as technology and science develop, they offer demonstrable evidence that at least in all observed instances, antecedent brain activity determines conscious choice. No such evidence seems to exist which demonstrates consciousness arising without any antecedent or encoded brain activity.


[1] O’Connor, “Agent Causation,” 265.

[2] O’Connor, “Agent Causation,” 264.

[3] Details of the study taken from John M Ostrowick, “The Timing Experiments of Libet and Grey Walter,” South African Journal of Philosophy 26, no. 3 (2007): 272, as well as from Sean A. Spence, The Actor’s Brain: Exploring the Cognitive Neuroscience of Free Will (Oxford: Oxford University Press, 2009), 127-140.

[4] Ostrowick, 273.

[5] Ostrowick, 273, quoting Libet, B. 1985. “Unconscious cerebral initiative and the role of conscious will in voluntary action”. Behavioural and Brain Sciences, 8:4 and Libet, B. 1985. “Theory and evidence relating cerebral processes to conscious will”. Behavioural and Brain Sciences, 8:4

[6] Ostrowick, 273-274. As Ostrowick points out, Libet’s assertion that vetoes do not possess antecedent unconscious brain activity seems to imply that they occur out of nowhere- hardly a better option. Ostrowick believes that Libet must either accept that vetoes have antecedent unconscious brain activity, or that dualism is the case.

[7] Sean A. Spence, The Actor’s Brain: Exploring the Cognitive Neuroscience of Free Will (Oxford: Oxford University Press, 2009), 126. Spence also discusses the discovery of a “neural correlate” to Libet’s “free won’t” view of vetoing as a regulatory action, 147-149.

[8] Though not treated in this post, O’Connor’s position can be found in the second half of “Agent Causation” and amounts to the claim that reasons can inform an agent’s decisions but not cause them. For a response to this aspect of O’Connor’s theory, see:

Feldman, Richard, and Andrei A. Buckareff. “Reasons Explanations and Pure Agency.” Philosophical Studies: An International Journal for Philosophy in the Analytic Tradition 112, no. 2 (January 2003): 135-145.

[9] Chun Siong Soon et al., “Unconscious Determinants of Free Decisions in the Human Brain,” Nature Neuroscience 11, no. 5 (May 2008): 543.

[10] Figure 1 from Soon, “Unconscious Determinants,” 543.

[11] Soon, “Unconscious Determinants,” 245.

[12] Soon, “Unconscious Determinants,” Supplementary Figure 6.

[13] Ibid.

[14] Spence, 128.

[15] Ibid.

[16] Spence, 128-129.

Here is a video regarding the study, courtesy of Machines Like Us:

  1. February 24, 2011 at 6:20 PM

    Thank you for outlining (and linking to) the study clearly. This has been a point of deep curiosity for me as of recent. Also, thank you for being honest enough to pre-empt criticisms.

    I am still hesitant to accept hard determinism of will across the board. This study, though deeply interesting and undermining of conventional views about free will, does not close necessitate determinism (as you have pointed out more adeptly than myself here and other places).

    • February 26, 2011 at 5:39 PM

      I always enjoy including potential criticisms to ideas I support, since I think it helps demonstrate that the ideas are indeed carefully considered and investigated. That being said, I might not have given enough credit to (1). As I am sure people like Timothy O’Connor are likely to point out, there does not seem to be an a priori reason for claiming that complex choices would obtain in the same way as simple choices, or a reason to believe that complex choices could be encoded. There is also the potential that such simple choices are governed by instinct or impulse, and complex choices are subject to deliberation. However, as I think my post demonstrates, I do not think such a counter is necessarily cogent since I am not aware of any similar work that an agency theorist could point to for support.

      While it does not necessitate hard determinism, I think it might necessitate hard incompatibilism, at least in the case of simple choices. This is due simply to what I see to be the Nemean Lion of the agency position: to have the most robust sense of freedom that our common sense picture of the world requires, action must come after deliberation, or at the very least consciousness, for such freedom to exist even in the hypothetical. The next Herculean task would be to demonstrate how such deliberation is not caused. Nevertheless this first hurdle must be overcome and this study certainly puts a dent in that endeavor.

      I think the next piece I’m going to write will address Derk Pereboom’s final section in “Living Without Free Will” where he claims that hard incompatibilism/hard determinism need not result in the belief that life has no meaning. From what I have read, this seems to be one of your primary concerns with accepting Determinism and has certainly been a blockade for many.

  2. February 27, 2011 at 3:51 PM

    Jared: I look forward to your subsequent posts. You are more aware of the Free Will dialogue than I.

    In a conversation with a friend recently he made the following comments about the video at the end of this post. I thought I would post them for conversation-sake.

    1. There is an improper inference being made when one says “I can tell you what you’re going to do 6 seconds before you do it.” What he means to say is “I can tell the causal story of your brain waves that will bring your body to act 6 s…econds before you do” But even that is flawed. There is no roadmap of brain states that tells you which one of them is the state of “desire” or “belief” as he says, so EVEN IF we granted him that EVERY mental state was reducible to some brain state (which it isn’t) then mass of brain state that represents a decision making process is far more complicated than telling the difference between a blue region and a yellow one. Saying the “blue region lights up when you’ve made a decision” isn’t telling me you can tell what decision I will make. If I asked you “Would you like peperoni or Sausage” it would be stupid for me to think that because some portion of your brain lights up when you make a decision…..that I can actually answer “sausage” for you…..for what brain state exactly images your decision that you want sausage more than pepperoni?

    2. Six seconds is enough time for the messages sent by neurons to travel to your toes and back….in a man who’s dying of old age (that means I’m assuming all neurons act as slow as possible) three times. In six seconds it is possible to make any number of decisions and it is equally possible to not even be thinking about the decision at the time. It is IMPOSSIBLE to even FATHOM what neurological science has the balls to say they can do. Predict people’s behavior huh? Alright….so when I’m thinking about Savanah Georgia on a hot afternoon with a glass of lemonade reading poetry on a front porch of a house that I made up………can you show me a picture of my brain and tell me precisely what color the house was, how tall the glass of lemonade was, or if the house was in the city of Savanah or just outside it?


    So to say that you know that THIS PICTURE of the brain is “The causally determinate path to the decision you made” is a fallaciousness. These kinds of claims are bold and brave and the experiments are wonderful……….but the claims are not coming from evidence they are finding in the experiment. The most that can be said about brain states as pertains to the will is that a few brain states act in tandem. But which brain states are responsible for which tasks is impossible to decider. The other problem I have is that these experiments often say “when you decide then do…so and so” so the decision is temporally prior to the action of reporting the decision……and then they go on to say that in your head they record your brain as having gotten excited BEFORE your report of having made a decision….which indicates we don’t have free will.

    Now, I don’t know about you, but I find it pretty obvious that OF COURSE my brain was excited BEFORE I REPORTED the decision………I was still MAKING the decision. And even WHEN the decision was MADE it takes WAY longer for my lips to move (or my hand to hit a button) then it would for my brain to state processing the information. That doesn’t entail the absence of free will……it entails precisely the kind of thing that one might SEE if one HAS free will.

    • February 27, 2011 at 5:58 PM


      Thanks so much for sharing the video with a friend. I think the study does a much better job of reserving judgment than the video, but I thought I would include it to make the post a little more interactive. If I can, I’d like to address the issues your friend had with the video’s claims in an attempt to reconcile them with the study.

      As a bit of a brief rejoinder to start with, I find it interesting that your friend attacks, in part, an overconfidence of researchers in their findings yet makes the claim in (1) that not all mental states are reducible – I would argue, as would Jaegwon Kim, as would Timothy O’Connor, that it is demonstrable (a priori) that all emergent mental states (and causal powers) are indeed reducible to the behavior of basal physical properties. I can provide citations and an argument for this if need be, but chiefly I wanted to point out that it is clearly not a matter of simply stating that not all mental states are reducible – there must be an argument made for this, otherwise it seems like posturing.

      (1)The video certainly might have misrepresented the study, since your friend appears to believe that the scientists make the claim they can predict any choice. This is not so. As I understand it, the way the predictions work is that the fMRI machine is fired up and observes brain states in multiple areas of the brain as the subject makes simple choices between Left and Right. With the knowledge of what choice was made, the computer then looks at what areas of the brain lit up more frequently when Left was chosen and what areas lit up more frequently when Right was chosen. From this, the colors are assigned to those areas so that researchers can look at the brain activity as it is happening and say “Well, the blue region is lighting up and we have a 65% probability that when this region is lit up the choice will be Left.” This is the nature of such predictions. The study could be conducted between any simple choice and I imagine the outcome would be similar. As for resolving how brain activity could indicate a choice, I am not sure why your friend does not understand this portion of the experiment. If you’d like I can e-mail you a PDF of the study – I just can’t post it for copyright reasons.

      (2) This is not so much a reasoned argument as it is disbelief in the findings of the study. With respect to the disbelief that brain states can encode choices due to the speed at which we normally perceive choices and activity, the simple response is that these were experimental circumstances. Surely the subjects were doing other things mentally and physically as they were being tested – thinking, feeling, twitching, etc. But this is not what was being studied; only a simple choice was being observed and there were certain controls in the study to prevent bleed over from other brain activity or to prevent flaws, i.e. a subject could not in quick succession press L, R, R, L, L, R, L all in one second. Even though such behavior is purely possible (and we no doubt can act much faster than this) the study was seeking to view brain activity over a measurable period of time. In this way, we can effectively toss out the 6-10 second window of prediction and merely say that the study clearly demonstrates that simple decisions are encoded in brain activity prior to consciousness. I do not see any way, based on the structure of the actual study and not the video, that this can be denied, though I am welcome to hearing how it can be.

      As for complex mental pictures, your friend is also mistaken. In a different but related study at Berkeley, brain activity was observed using an fMRI machine while subjects viewed one out of 120 photographs. 72%-92% of the time the computer was able to correctly identify what picture the subject was looking at based purely on brain activity. This predictive power was based on the computer observing fMRI data from the subject viewing stock photos of various objects and scenes, etc. and the brain activity was narrowed in much the same way that I outlined above in this comment. The abstract of the study can be found here: http://www.nature.com/neuro/journal/v12/n3/abs/nn0309-245.html and an ABC report on the study can be found here: http://abcnews.go.com/Health/MindMoodResourceCenter/story?id=4396370&page=1

      So, in short, yes the same sort of test can be used to ascertain whether your friend is looking at a picture of Georgia and whether s/he is looking at a picture of England, or a tree, or a friend, etc. While this is not the same as a computer predicting WHAT you are thinking about, an extreme extrapolation of this test, if the computer were given months and months and months to compile data on your brain states, it is not out of the question that it could figure out what you are thinking based purely on your brain states. This seems to be more evidence that more mental states than your friend is willing to admit are reducible to brain states.

      As for this:
      “The most that can be said about brain states as pertains to the will is that a few brain states act in tandem. But which brain states are responsible for which tasks is impossible to decider. ” I again appeal to the study itself and not the video, and ask how exactly the isolation of areas of the brain, coupled with the predictive capacity, do not entail that mental states of simple choices are not reducible to brain states.

      As for this:
      “The other problem I have is that these experiments often say “when you decide then do…so and so” so the decision is temporally prior to the action of reporting the decision……and then they go on to say that in your head they record your brain as having gotten excited BEFORE your report of having made a decision….which indicates we don’t have free will.” Again, as I concede in my post, there is a certain issue with having the subject report when s/he became conscious of the decision. But even if we grant a very large gap of 2 seconds for the subject not being sure about when they actually became conscious of having decided which button to push we are still left with a very wide margin where brain activity that matches quite closely with how the subject ends up deciding is going on without the subject being aware of this. I do not think this can just be explained away as your friend seeks to do.

      As for the study not demonstrating an absence of free will, this was not the claim made in the study and I do not believe it was the claim made in the video either. All that is being said is that the mental states of simple decisions appears to be reducible to brain states that occur prior to a subject becoming conscious of his or her own decision to act. Even if we grant that there is some sort of “free” or “quantum” element at work PRIOR to the brain activity that actually sets it off, this is still not the type of freedom of the will that your friend, or any agent theorist, is talking about. This is because such “freedom” does not occur from deliberation and so I am not sure in what sense it can be said to stem from any sort of agent, soul, or mind, since it occurs PRIOR to brain activity which occurs PRIOR to consciousness. This is not at all what we would expect to see if we had free will – if we had free will we should expect that (1) any brain activity occuring prior to the moment of consciousness is preperatory (i.e. preparing the agent to decide) but not predictive in any way, even looking at past actions, etc. (2) after the moment of consciousness a flurry of brain activity as the agent deliberates as to which button to push, still with no predictive element. This is clearly not the case given the outcome of the study.

      If I am understanding your friend’s issues with the study, I believe these responses address them, but I certainly welcome your friend to come by and post his or her thoughts about the study. I might put up a similar post on the Berkeley study if I have time after the Pereboom post. Thanks again, Nick!

  3. Dirk
    June 14, 2011 at 8:35 AM

    Dear Jared,
    While fully admitting that predictive brain activity has been demonstrated by Libet et al. and Soon et al. to occur prior to a subject’s consciousness of making a decision, there are some elements that in my opinion are left out of consideration. I mean that the test subjects, having heard the instructions given by Libet or Soon, are fully aware of the situation that they are expected to make a ‘free’ decision for a movement or choice, that they have to act accordingly if they are willing to do so, and that they must keep an eye on Libet’s clock or Soon’s letter stream. Instead of only speaking about the readiness potential that is generated by the supplementary motor area, or about the frontopolar cortex and parietal precuneus, the sequence may be enlarged by also pointing to the fact that the abovementioned conscious elements precede (and later also accompany) the frontopolar and parietal brain activities. The whole sequence therefore starts eventually with these conscious elements (and the brain states these elements refer to). I wonder whether the recognition of these elements may alter somehow the usual conclusion that a subject’s decision for a particular choice finds is preceded by and dependent on unconscious brain activity. I look forward to your reply.

    • June 23, 2011 at 2:52 AM


      Thank you for visiting my blog and taking the time to thoughtfully respond to my post. I hope my response can get at the heart of your questions. To that end, I see two primary prongs to your criticism and I do believe I have appropriate responses to both.

      (1)The first part of your criticism is that the very nature of the experiment, i.e. testing conditions and the general artificial nature of the experiment might exagerate or otherwise skew the results. Specifically, you mention that the participants’ knowledge of the parameters of the experiment would indicate that they are not truly making a “free” decision, since they are there solely to perform the task required by the experiment, and are expected to comply. First, you are correct that all experiments are artificial in that they attempt to recreate an event or occurance in a controlled setting while also removing confounding variables. However, we currently do not have many other options in terms of recreating events in order to study them, and so a certain level of artificiality is appropriate.

      That being said, I do not agree that the artificial structure of the experiment calls into question the findings, i.e. how relevant the predictive capacity of brain activity is with regard to the study. This is because the point of the Libet and Soon experiments was to measure the timing of brain activity compared to consciousness and to action. What action – whether wiggling a finger or pressing a button – matters very little. For this reason I do not think it proper to claim that simply because I know I must, at some point, press one of two buttons that suddenly the predictive power of brain activity paired with the MRI scans are meaningless. Certainly, actions and thoughts that arise organically seemingly MUST occur much faster than in the many seconds the study represents. This, however, is the point of the study: to elongate these very short and quick instances to the point where we can examine them in order to demonstrate that unconscious brain activity does, indeed, precede action and, further, it is predictable based on brain activity.

      (2) The second part of your criticism centers on drawing attention to the artificiality of the experiment by way of elongating the sequence of events itself to include the subjects’ knowledge of the parameters of the test. If I understand this portion correctly, you seek to argue that participation and knowledge regarding the test itself might constitute a conscious and ‘free’ choice, which would more appropriately be viewed as the ’cause’ of the actions taking place in the study. While you are certainly correct in pointing out that participation in the test is consent to act according to the parameters of the test, I would point to the findings of the test itself. If we generalize the findings (and I cannot see a prima facie reason why we cannot) then even the conscious acceptance of the test and whatever other states or actions you deem ‘conscious’ must necessarily themselves be preceded by determinant unconscious brain activity. The simplest argument for this answer is: why would there be determinant unconscious brain activity prior to conscious thought during the test but not for conscious thought prior to the test? So, while for every determinant unconscious brain state that exists there might very well be a linked or relevant conscious state prior to that, this conscious state would itself have an antecedent unconscious brain activity which determined it.

      In this way, I do not think these considerations alter the conclusion of the studies. I hope my responses are adequate, and I am more than happy to continue the dialogue even further! Also, thank you for your patience in awaiting a reply – I have been on an extended ‘vacation’ with numerous obligations. I thought it only fair to give your thoughtful comment a fitting reply.

  1. September 14, 2011 at 7:58 PM

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