Friday, 18 April 2008

Libet Redux: Free will takes another hammering

The scientist Benjamin Libet shocked the world in 1985 when he published research showing that preparatory brain activity occurs several hundred milliseconds prior to when people consciously choose to move.

His experiment suggested free will is an illusion. But there were problems with this interpretation. For example, the apparent lead time of the preparatory brain activity was so short that some critics suggested it could be accounted for by the inaccuracy of people's reports of when they'd made their conscious decisions to move.

Now, using modern brain imaging methods, Chun Siong Soon and colleagues have replicated and extended Libet's famous study - once again reinforcing the notion that our sense of free will is an illusion.

Participants had their brains scanned while they decided to press a button with their right or left index fingers. Participants referred to a constant stream of changing letters, visible on a screen, to indicate when they'd made their decision. Around ten seconds before participants reported making their conscious decision, patterns of brain activity in two areas correlated with the decision they would go on to make. These regions were in the frontopolar cortex and the parietal cortex.

Unlike Libet's study, which reported non-specific preparatory activity, the current experiment showed it was possible to use brain activity to discern which of two options a person was going to choose from, well before they consciously knew which choice they'd made.

Meanwhile, activity in the same movement-related brain area reported by Libet - the supplementary motor area - predicted when the participants would move, up to five seconds before they consciously decided to.

"Thus a network of high-level control areas can begin to shape an upcoming decision long before it enters awareness," the researchers concluded.

Link to earlier related Digest item.
Link to another related Digest item.
Link to essay arguing free will is not an illusion.
Link to recent journal special issue on free will.
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Soon, C.S., Brass, M., Heinze, H., Haynes, J. (2008). Unconscious determinants of free decisions in the human brain. Nature Neuroscience DOI: 10.1038/nn.2112

Post written by Christian Jarrett (@psych_writer) for the BPS Research Digest.

24 comments:

  1. In my view, the problem with this whole free will debate is that people rarely define what they mean by the term, and there are two very different implicit definitions that are being used.

    Definition 1: Humans can think about different courses of action and then choose based on their thoughts.

    Definition 2: There is a decision-making capacity that's independent of physiology.

    Obviously, there is a free will in sense 1, but not 2. That's pretty much the end of the debate in my book.

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  2. Anonymous11:20 am

    This doesn't reinforce anything about free will being an illusion. Unless, you have some very specific idea of about what free will is, which would be very silly since we don't have enough scientific studies on free will to be that specific in the first place. That's if you believe that it is possible to actually to prove something about free will either way to begin with. We also don't know enough about neurology, either, to make such logical deductions about free will assuming we were all on the same page in that area.

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  3. People feel as though they make decisions consciously - that's the key point. This research suggests that decisions are formed in the brain first, beneath the level of consciousness, and that we only become aware of that decision sometime afterwards, at which point we (i.e. our conscious selves) experience an illusion of ownership over the decision.

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  4. Anonymous4:39 pm

    The study is interesting, but the title incorrect.

    The issue here is not about free will. It's about (levels of)consciousness/awareness and embodiment of decision.

    Since this is a scientific publication, why confuse the readers with a newspaper-like title?

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  5. Anonymous: Can you explain why a study about conscious awareness of decisions is not about free will? I think it is, hence my choice of title.

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  6. Anonymous7:49 pm

    Why the title is incorrect/unfortunate?

    Because, while taking into consideration the various processes, creates confusions.

    Before a decision is reached, the huge network that is our body engages in this process. The time delay/gap between patterns of brain activity; initiation of action/movement; and being fully aware/conscious of this fact, does not mean that free will is an illusion.

    This is just how the process unfolds, how our complex body functions, employing many processes of which most are not conscious.

    Did PARTICIPANTS wanted/decided to press the button?
    YES.
    Then this was, their, free will. Which did not take any hammering.

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  7. No anonymous: they were instructed to press one of the buttons - so that's the boring bit. The crucial, possibly 'free', choice was over which button to press and when. The participants' conscious sense of when they freely chose which button, and when, came after nonconscious activity in their brains, which was predictive of the choice they would go on to make. That is, the choice of which button and when felt like it was made freely by their conscious selves, but it seems it wasn't. The free will debate isn't over. But I'd say the pro camp have taken a fresh hammering.

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  8. Mike Lawrence1:23 pm

    I wonder: How many science bloggers & journalists bothered to read the supplementary material to this article? Those who did might have noticed this tidbit:

    "Importantly, in order to facilitate spontaneous behaviour, we did not ask subjects to balance the left and right button selections. This would require keeping track of the distribution of button selections in memory and would also encourage preplanning of choices. Instead, we selected subjects that spontaneously chose a balanced number of left and right button presses without prior instruction based on a behavioural selection test before scanning".

    A stunning piece of methodological incompetence if I've ever seen one. Let's instruct people to avoid X then only choose those participants who manifest behaviour that matches what might be produced if they ignored our instruction.

    This control failure could account for their entire result. The period of predictive activation could represent accessing memory for the last response or some calculation of the average number of left/right responses. When this stage returns a value of right-last(left-last) or right-more-often(left-more-often), the subsequent response is more likely to be left(right) in a participant who is trying to balance responses.

    I'm no advocate of free will (colloquial or Dennett-esque redefined flavors), but in the tradition of Libet's original work, this is just shoddy science that does not bear on the question.

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  9. Minor corrections:

    1) I implied above that the authors explicitly instructed against balancing responses, but clearly in the quote I cite they did not even raise the issue with participants beforehand. To my mind this in fact increases the likelihood that participants selected by the authors were those that of their own accord attempted to balance their responses

    2) My name above links incorrectly, it is fixed in this post.

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  10. speaking of methodological incompetence... one more try at that link! (presumably because someone cares :Op )

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  11. Anonymous2:34 pm

    My last reply to digest about the inappropriateness of the title.

    digest said:
    “The participants' conscious sense of when they freely chose which button, and when, came after nonconscious activity in their brains, which was predictive of the choice they would go on to make. That is, the choice of which button and when felt like it was made freely by their conscious selves, but it seems it wasn't.”

    While you type your message, are you conscious of absolutely all processes that take place in your brain, and indeed in your body, of which the brain is just a part? Of course you are not. Yet it is you who initiates the thinking and actions that lead to the message you are typing. Without your free will/decision to engage in typing the message, there would be no message posted by digest.

    The fact that you become aware of the decision you take after a slight delay is secondary, it’s just part of the overall process that involves countless non-conscious/subconscious processes taking place in the whole body. Yet it is you who decides and acts as a whole person/being/animal.

    A mistake is that you equate free will with awareness/consciousness of all processes involved in decision-making. A second mistake is that you expect a specific part of the brain to give the answer about the existence of free will, while in fact that specific part is operating within a network, and it is the whole network/body that takes part, in conscious and non-conscious/subconscious processes.

    This is why nonconscious activity in the brain - which is integrated in an overall complex process leading to an outcome - was predictive of the choice participants would go on to make.

    It was their choice, and their free will, regardless of the slight time delay in becoming aware of the outcome/action they were engaging in.

    Sometimes a tree can prevent us from seeing the forest…

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  12. Anonymous said: "Without your free will/decision to engage in typing the message, there would be no message posted by digest".

    I don't think there is any dispute that courses of action are being selected and acted upon. The interesting bit is whether *we* freely choose those actions. And I think most people equate the *we* in this debate as their conscious selves. Of course this perspective risks slipping into a dualist discourse, but then who would be interested in a free will they had no conscious control over? In fact isn't that a contradiction in terms? In short, nothing you (anonymous) have written so far, has persuaded me of your astonishing claim that this study is irrelevant to the free will debate.

    Mike Lawrence: You raise an intersting point and I'm planning to go back to the paper (and supp material) to check out your claims.

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  13. Digest, you said:

    "The interesting bit is whether *we* freely choose those actions. And I think most people equate the *we* in this debate as their conscious selves. Of course this perspective risks slipping into a dualist discourse, but then who would be interested in a free will they had no conscious control over?"

    A few points, all only on the basis of the press coverage of the paper:

    1. If that's the point of the study, then I don't see how it improves on the many studies that show that you can influence actions by subliminal priming (besides identifying the relevant brain parts and putting a "time tag" on it).

    2. I guess most people would agree that most people's actions are influenced by forces outside of their consciousness. Effects of advertising come to mind.

    3. Saying that an action is under conscious control isn't saying that all of the influences on the preferences leading to that action are under conscious control. Icek Ajzen made pretty much the same point.

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  14. Lemmuslemmus: Sure, external influences can affect our behaviour in powerful ways and the research on that is facinating too. Indeed, there are influences caused by stimuli that we can't consciously detect (because they're too quick, or not bright enough etc) and there are also nonconscious influences from stimuli that we can consciously detect, but we don't realise the effect they're having on us. I wrote about this stuff for The Psychologist last month. I would agree, that research also undermines our sense of free will. But this study is a bit different because it's about simple, internally generated, volitional actions which feel as though they are under our conscious control. I think it is interesting to discover that activity predicting the choice of button press comes before the conscious sense of having made the decision.

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  15. Anonymous7:47 pm

    1. Free will and internally generated, volitional actions, is one thing.

    2. Conscious control over how all networked processes in our sophisticated bodies function is a totally different thing.

    Expecting conscious control over this is illusory. And such illusory conscious control does not have anything to do with free will, as it is not you who decides how each bit of your body functions; or the order, and time delay, between the various conscious or nonconscious integrated processes.

    It is of course “interesting to discover that activity predicting the choice of button press comes before the conscious sense of having made the decision”, as you said.

    But this simply means discovering little bits about how we function.

    It does not contradict/hammer the notion of free will, simply because this is not at all about free will/internally generated volitional actions.

    This is why your title/conclusion is incorrect/unfortunate.

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  16. Anonymous, you said "Conscious control over how all networked processes in our sophisticated bodies function is a totally different thing."

    No-one is saying anything about conscious control or awareness of all bodily functions. We're discussing free will - the act of make a deliberate, conscious choice. This study suggests our choices are not instigated by our conscious selves. They are initiated nonconsciously first and then only afterwards do we become aware of having made a choice, except we don't experience this feeling veridically. No, we experience the illusion that our conscious choice instigated the process. I've already said this is not the end of the free will debate, but the idea that this has nothing to do with free will is ludicrous. If you want to convince me that the title is inappropriate, you need to explain what is free about a choice that you have no conscious control over, or conscious access to, at the moment it is conceived. Just saying that our bodies are very complicated and we can't be conscious of everything won't wash. It's the moment of will, the instant of choice we're talking about here. Are we driving this thing, or mere backseat passengers? This study suggests, though by no means proves, we're sat in the back.

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  17. Mike Lawrence: I checked out your interesting point. The authors put aside considerable space in the supplementary material answering your specific criticism. They argue there are many reasons for believing that the predictive neural activity is not related to the carry-over of information from previous trials, but is only associated with the current trial. To take just two reasons: the pattern of participants' responses appears to be random and the predictive accuracy preceding a decision grows in accuracy with increasing time since the last trial.

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  18. Anonymous1:11 pm

    Digest, you said:
    “If you want to convince me that the title is inappropriate, you need to explain what is free about a choice that you have no conscious control over, or conscious access to, at the moment it is conceived”.

    In the cited experiment, there is no question that participants’ free will was manifested in their deliberate choice over what button to press and when. Their choice was instigated by them.

    The part that creates confusion/debate is about “the moment it is conceived”, the "moment of will, the instant of choice", which you thought should be the moment of awareness of decision.

    One answer is that we can not specify an exact “moment/instant” when a choice/decision is conceived, because this is actually an unfolding complex PROCESS.

    While engaging in the decision-making process, mental and physiological changes took place in participants’ bodies, most of them outside conscious control or conscious awareness. Some of the brain activity during this process preceded the moment of awareness, whereas other elements of the process followed it, even allowing for the decision to be cancelled/changed at will before being carried out. Our intelligent bodies are designed to work like this, and this does not cancel the notion of free will.

    We don’t choose, at our will, how the body carries out a decision-making process when, for example, we decide what button to press. But we do press the button we want. And this is an outcome of our free will, regardless of the moment/instance we become aware of this during the decision-making process.

    In other words, when using our free will, we decide about something - an object/behaviour. But not about how the body will integrate all its subsystems, or the order and timing of all mental and bodily events during this process.

    Therefore, my argument is that (i) decision-making is a process, a large part of which falls outside our awareness, process that can not be reduced to a precise, single moment or only to a specific part of the brain that gets activated during this process; and that (ii) the intelligently orchestrated succession of conscious and nonconscious processes taking place in our bodies during a decision-making process falls outside the remit of free will, because they are not the object of our free will.

    Separate from this, I think it might be interesting for future articles if you could also report on studies showing how unconscious processes, or electro-magnetic fields - to give just two examples - interfere with, or manipulate, our free will.

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  19. Justin Bell4:56 am

    digest: But the way you are talking about it makes it seem as if the way free will works equates to if free will exits or not. Saying that it's another hammering for the free-will camp is an argument based on some non-scientific, preconceived notions about what free will is and how it works, and therefore it says nothing in a scientific test.

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  20. Non Serviam4:47 pm

    The results have not shown that free will does not exist but rather that it takes time to form Dennet would argue. In everyday trivial decision making we do the work without being aware of doing it - it is not needed because we have already learned to do it; like pressing notes on a guitar after the song has been learned. Awareness is not free will. What this research shows is that we should not think of our selves as being our conscious selves but rather the whole package, conscious, subconscious, unconscious. It is all part of what manifests and it all takes part in who we are.

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  21. Non Serviam4:53 pm

    Perhaps a more appropriate title would be: Control by the Cartesian Ego takes another hammering

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  22. Interesting. I just read an interview of neuroscientist Jill Bolte Taylor in the April 19, 2008 edition of New Scientist titled "Rebuilding your own mind" that would seem to refute the analysis of this study. In it, she discussess healing from a stroke she had, where she felt she was consciously choosing how to rebuild her brain. Her response to the question "Did you actually consciously reconstruct your brain with your thoughts?" is most intersting. I quote: "Yes, rerunning or renewing neurocircuits was a cognitive choice. The non-functional circuits started to come back online one at a time and I could choose to either hook into that circuitry or not feed it. For example, when the anger circuit wanted to run again, I did not like the way it felt so I said 'no' to its running..." Sounds like free will to me.

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  23. Anonymous11:21 pm

    I don't understand this study, but in my own personal experience, I used my "will" to get out of some pretty difficult situations.

    Of course my biology, background and environment plays an important role, but there is still a "Me" that didn't give up, that kept presevering and eventually succeeded.

    I also believe that I deserve credit for that.

    However, my "will" isn't all powerful. I've had alot of people chastise me for not "willing" myself to get better or succeed. But, it's not that easy, and I am vulnerable: I can be placed in situations where I would be overwhelmed and there is not enough "will" to pull me through.

    Also, it's a study - and only one. It's interesting that people are quickly jumping to conclusions and no one seems to be cognizant of the fact that this is the first step in helping people deal with schizophrenia, etc.

    With regards to the penal system - I always felt we should take the person's life into account: Is it reasonable to assume this person could have the "will" to act otherwise? There's no standard really for everyone.

    I plead human (with finite amount of free will).

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  24. Anonymous2:20 am

    "Around ten seconds before participants reported making their conscious decision, patterns of brain activity in two areas correlated with the decision they would go on to make."

    I am curious. Every day I cross two eastbound lanes of traffic to merge into the westbound lanes. The cars in both lanes are traveling at least 40 mph (19.6 yds/sec), and the ones in the westbound lanes emerge over a hilltop not 60 yards away. Is my very conscious thought, "Go now," the result of a process that begins 7 seconds before I see the last car come over the hill? Is this a test hammering free will, or one proving prescience?

    Please tell me what I am missing.
    Sincerely,
    Anonymous II

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