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The Neural Basis of Free Will: Criterial Causation by Peter Ulric Tse (MIT Press, 2013)

The views expressed are those of the author and are not necessarily those of Scientific American.


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What is free will, and how can it be generated by a neural circuit? The problem may seem, at first, like a fairly trivial issue. It seems evident to each of us that we wield free will. It feels like the world is our oyster—that with our wit and our will power we can overcome adversity.  But the problem is actually deep, and it even precedes science in that it’s fundamental to religion as well. If God is perfect and knows all our fates, the Jesuit quandary goes, then the future is known, at least to Him, and therefore how can there be free will since every decision for the entire expanse of eternity has been laid out, unchangeable? There can be no real decisions, if true, no matter how free they seem. No matter how random or how spur of the moment any given decision was made, God knew you were going to do that.

The scientific version of the same quandary is not too different. Laplace imagined a similar scenario based solely on a universe of particles. Think of the universe as a billiards table, and all the particles in the universe so many billiards balls. If you could know all of the vectors of all the balls on the table, and all of the physical rules by which balls interact with each other—and with the table itself—you could predict any future position for the balls on the table. All possible interactions could be simulated forward to any future point in time. But even in a billiards table (or other closed system, like, say, the universe) where you don’t know every vector exactly, this line of thought suggests that although you cannot to predict the future accurately, you nevertheless know that future is predictable. That everything in such a universe is fated to happen.

If our universe is deterministic in this way there can be no free will because you were destined to make that same decision—every single one of your decisions—from the very moment of the big bang. It’s not that you don’t make decisions: you do. But you’ll make them the same exact way in two different universes that have identical big bangs. It means that the universe conspired from its very inception to bring you and your significant other together. It’s quite romantic, actually, so long as you’ve been fortunate enough to have a nice life. But if not, you’re truly screwed, and the universe has been literally plotting your demise for the last 14 billion years.

For some physicists, these issues are not really issues at all because the universe, they claim, is not deterministic. That is to say, quantum level effects on particles are truly random. Therefore, the same big bang, if it occurred twice in two different universes made up of exactly the same particles having identical initial vectors would result nevertheless in different futures, because quantum level random effects change things up. Other physicists, including Stephen Hawking, poo-poo the quantum gambit, instead concluding that quantum effects may randomize particle vectors a bit at a low level, but only on such a minute scale that irrelevant to human life, and that the universe is, for all intents and purposes, deterministic. That rings true with me—quantum mechanics predicts that everything is possible with varying levels of probability, but that means that the way things are would probably happen again and again, given the same big bang and the same universe of particles, in each iteration.

So the universe is either deterministic or non-deterministic, and your free will to choose the red versus the green sauce for your burrito hangs in the balance. First, why would there be a problem with free will? A blade of grass rotates to follow the sun throughout the day in a process known as heliotropism. But does it intend to follow the sun? No, it’s just a chemical reaction, its basis is known, and it’s straightforward to explain. To be clear, I reject the idea that the blade of grade is conscious at some low level. That’s silly. Ok, now, what about if you take a neuron—a brain cell—and stick it in a dish with all the nutrients it needs, then spritz neurotransmitter on it. It responds with a vigorous burst. Did it intend to burst? “Well, ah, noooo, I guess not”, you might say, with some discomfort, as you realize that your brainpan is merely a dish that provides all the nutrients your brain needs, and the neurotransmitters on each neuron are all provided from other neurons in the same dish.

Making your will even less free, research in John-Dylan Haynes’s lab at the Bernstein Center for Computational Neuroscience in Berlin, Germany has shown that an upcoming decision being made by human volunteers can be predicted from brain scanning data, at levels better than chance, up to 10 seconds before the volunteers know what they themselves are going to decide. So unconscious processes are thus actually in control your decision making long before you even know you’re making a decision. Whoa!

So that’s it, we’re done, there is no free will, right? The universe can’t sustain it, your brain has made up its mind before you have, and you have merely experienced the illusion that you’ve been in control since the moment you learned to crawl and discovered the feeling of agency.

Not so fast. Enter Dartmouth neuroscientist Peter Tse, who has found a middle ground in his new book “The Neural Correlates of Free Will: Critical Causation” (MIT Press). Tse has thought through this enormous problem and realized something important that brings free will back to the realm of the living. Remember that determinism is an unavoidable fact of the universe at the macroscopic but not the quantum level. Well what if the macroscopic universe is not deterministic because the brain is designed to amplify quantum level particle effects to the macroscopic level through the action of specialized neuronal channels that make decisions potentially truly stochastic?

There are chemical receptors on most neurons that receive neurotransmitters (globs of chemicals secreted by other neurons), that then respond by opening ion channels, causing neurons to create neutral impulses (aka: macroscopic real world events normal people call “brain activity”, or “thought”). Well, in a deterministic universe… so what? You could have predicted every idea I’ve ever had, before my birth, if had enough data about the universe. Right? Tse says no, because some chemical receptors, called NMDA receptors, are actually blocked by a single atom of magnesium, that must first be released before ions can flow to cause brain activity. Because macroscopic brain activity is therefore dependent on the position of a single atom, which is itself a quantum-level creature, it means that these neurons amplify the quantum level activity of the magnesium atom to the level of neural circuit behavior and real life. Thus our behavior is indeed subject to quantum effects and the universe cannot be deterministic.

I love Tse’s book. It has literally set me free. It explains these ideas in full glory, in exquisite detail, and much better than I can summarize here.

Added post-hoc: Author Peter Tse contracted me and thought that some  potential reader  questions could be clarified by noting that the brain works as a coincidence detection machine at the neuronal, dendritic and receptor level, and that quantum level randomness has its effects by randomizing spike timing, and therefore  this determines what will count as a coincidence. Also, a key idea of the book is that certain brain circuits associated with planning can change synaptic weights extremely rapidly, so that neurons  can respond differently to same inputs, even within a short period of time based on the rapid synaptic weight changes brought about by quantum level effects. This can change the information that neurons are responsive too, so that the neural code becomes not just a spike code, but a synaptic weight code. For example, executive circuits might set the criterion that memory circuits should recall a politician. Margaret Thatcher might come to mind, because she meets that criterion. But from the exact same initial conditions, Obama might also have come to mind. Which came to mind was a matter of chance. This is not deterministic, because the outcome could have turned out otherwise. But it is also not random, because the outcome had to be a politician.

Stephen L. Macknik About the Author: Susana Martinez-Conde and Stephen L. Macknik are laboratory directors at SUNY Downstate Medical Center. Follow on Twitter @illusionchasers.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Dave W. 11:05 pm 08/12/2013

    Free will involves conscious control of thought processes. Finding the universe and/or the brain is non-deterministic doesn’t return control to the brain. You would have to find a mechanism through which a person chooses to harness those quantum effects magnified to the macro world during a decision-making process. Otherwise, Tse has only found a way that a person’s “decisions” are the result of quantum dice-rolls – that if we “replayed the tape,” different decisions might be made, but still with no sign of free will evident.

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  2. 2. SBujarski 11:06 pm 08/12/2013

    While I understand the desire to draw from quantum mechanics to free us from determinism (and indeed very convincing arguments can be made that quantum fluctuations do throw Laplace’s demon out with the bath water) I do not see how this rescues the idea of human free will. The argument that truly random (or probabilistic) fluctuations in the behavior of single atoms govern some aspects of nerve function does not lead to the conclusion that “you” freely chose anything. Such an argument is still claiming that neurons, which follow physical laws of the universe (whether deterministic or not) are wholly responsible for the decisions you (in the subjective sense of the word) make. Here’s a thought experiment to clarify this. Imagine I could hook up the neurons in your striatum (or any part of the brain for that matter) to fire according to a true random number generator. This situation would certainly be less deterministic than quantum probabilities governing the behavior of a single receptor type. In this experiment you could no more claim that your decisions were freely chosen than if Laplacian determinism were true, because the firing of your neurons outside of your subjective awareness led to your decisions, not the other way around. Merely introducing randomness to the behavior of neurons does not insert the subjective you as the author of all your thoughts and decisions. In my opinion, true free will would require not only the falsity of determinism, but a mechanism through which conscious awareness, separate from the behavior of physical entities like neurons or atoms, made decisions.

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  3. 3. looie496 11:51 pm 08/12/2013

    It’s certainly plausible that brain circuits amplify quantum fluctuations to macroscopic scales — brain circuits are almost ideal for creating a “butterfly effect”. But I’ve never been able to understand why so many people think that a decision made by rolling dice is somehow freer than a decision made deterministically — even if they’re real, true, honest-to-god *quantum* dice.

    Regards, Bill Skaggs

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  4. 4. aleandrade 8:47 am 08/13/2013

    Reading the article, it seems to me that our decisions might be random, which does not mean that they are free.

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  5. 5. jyudin30 9:02 am 08/13/2013

    “**If our universe is deterministic in this way there can be no free will because you were destined to make that same decision—every single one of your decisions—from the very moment of the big bang.”

    **guest editors note: There is a prominent philosophical notion known as compatibilism (or soft determinism) which postulates that free will can be reconciled with determinism. The two are thus compatible when defining free will as an instance in which the agent had freedom to act according to their own motivation.

    The argument for compatibilism goes as follows–Imagine two different lottery formats.

    1) One is the traditional lottery format where tickets are purchased prior to the numbers being drawn. After the purchasing period has stopped the numbers are drawn.

    2) In the second lottery the numbers are drawn before the tickets are purchased. The numbers that are drawn are completely unknowable by the purchasers and placed in an inaccessible vault until the time for purchasing tickets has ended.

    Are the chances of winning the lottery any worse in the second lottery format? Did determinism constrain your ability to choose the numbers? Thus as Danniel Dennet would say: If you answered “no”..you might be a compatibilists.

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  6. 6. August Berkshire 10:14 am 08/13/2013

    By its very definition quantum indeterminacy can’t be determined, thus we can have no control over it, thus there is still no free will.

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  7. 7. gubbler chechnova 10:50 am 08/13/2013

    “If God is perfect and knows all our fates, the Jesuit quandary goes, then the future is known, at least to Him, and therefore how can there be free will since every decision for the entire expanse of eternity has been laid out, unchangeable?”

    Not necessarily. If God is all-powerful, He can create a zone or sphere in which His will is not directly applicable and in which He cannot foresee the future. It is paradoxical to be sure but conceivable.

    We humans are not all-powerful, therefore we cannot un-know what we know. We all know what an elephant is, and no matter how much we try to un-know of its existence, we still know what an elephant is. But if we were truly powerful, we would be able to un-know the fact of the existence of the elephant.

    If God is all-powerful, He could created a zone in the universe in which His will and full knowledge don’t apply.
    It’s like Superman cannot see through lead. God can willfully place ‘lead’ between His knowledge and the secret box known as the world of men. God knows but also has the power to un-know.

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  8. 8. gubbler chechnova 11:02 am 08/13/2013

    Free will is meaningless in relation to the universe since stars and meteors have no consciousness.
    Free will is only meaningful in relation to man. Though man is like an organic machine, it is possible for men to reflect on his life and decisions and realize how they might have been wrong. It is on this human level that free will has any meaning. It’s about the ability for introspection that allows individuals to break out of cultural conditioning. Such men are rare but they exist. Buddha, Socrates, Jesus.

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  9. 9. jayjacobus 11:23 am 08/13/2013

    Determinism depends on the starting point. Start with potentials and explain how potentials were deterministic before there were any natural laws. Were the natural laws selected deterministically from potential? Before the big bang where did potential come from and what was the (deterministic?) trigger that started the big bang?

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  10. 10. Arun 11:35 am 08/13/2013

    Nice article. Do we have a consensus of what counts as “free will” or not? I do think there is something along the lines of it, mainly because we’ve evolved to a point at which we can look at ourselves and ask if we have it (free will, I mean).

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  11. 11. davenussbaum 11:53 am 08/13/2013

    Sounds like an interesting argument and book, but I have one clarifying question:

    Isn’t this an argument that our choices have an element of randomness rather than being determined — not that our will is free? After all, we don’t have much choice in determining whether that atom of magnesium is one position or another. What’s the step between our choices being free from being pre-determined and actually being free?

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  12. 12. zstansfi 12:24 pm 08/13/2013

    In writing this essay it is apparent that you have failed to understand the most fundamental problem with free will.

    In a non-deterministic universe, where decisions are determined by stochastic physical events, then how do I have any free will? Choice in the colloquial sense is impossible because my decisions are predicated upon randomness.

    Did I *choose* the position of the magnesium ion placed inside or outside of the NMDA receptor pore? Of course not, this is ridiculous. Free will cannot be found in quantum mechanics.

    Herein lies the rub: free will assumes a deterministic universe, because in the absence of determinism, my choices do not lead to specific actions, but could have a random variety of outcomes. But, in a deterministic universe, I have no free will unless we additionally assume that processes placed outside this universe can overcome these physical laws to enact a “willful action”.

    This paradox cannot be undone simply by conjuring up quantum theory and applying it to a popular receptor mechanism with no relevance to free will.

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  13. 13. Big Questions Online 12:41 pm 08/13/2013

    If you’re interested in free will, please join a new online discussion, “Does Belief in Free Will Make Us Better People?” https://www.bigquestionsonline.com/content/does-belief-free-will-make-us-better-people

    UCSB prof.and leading researcher Jonathan Schooler is responding to comments through Monday, Aug. 19. We welcome your contributions.

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  14. 14. dburress 4:45 pm 08/13/2013

    I really don’t get this free will/determinism quandary. Why is being random any better than being determined? To my mind Hume blew this argument out of the water long ago. Both causality and randomness are testable operating assumptions we make in some specific cases that sometimes work. If one doesn’t work we change the assumption, or perhaps we give up. They are not testable feature of the universe as a whole. Even if quantum mechanics were both true and random in our corner of universe, it could be deterministic in a larger universe that is not observable to us: God could bias the dice using undetectable angels. Even leaving that aside, we will never know with with certainty that quantum mechanics is “true.” It remains a best guess based on operating assumptions.
    When I say I have free will, it has nothing to do with this kind of issue. What I mean is two things, both of which are scientifically testable:
    1. I can take action based on a decision process such that the process really does lead to the action. Granted that some of that process is necessarily unconscious, nevertheless I can review its logic in my conscious mind and see how that process leads to that outcome.
    2. I can take actions that you absolutely cannot predict without eavesdropping on my mental process. For example I can take what are from your point of view truly random actions. One way to do that is to use a pseudorandom number generator calculated inside my brain to decide between alternatives. Or I could use truly random seed for the generator based on events such as the last digit in microseconds of the moment I turn on my computer.
    David Burress
    Lawrence KS

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  15. 15. Stephen L. Macknik in reply to Stephen L. Macknik 7:18 pm 08/13/2013

    Thank you for your comment, please see the addition made post-hoc to the post, as it may clarify things.

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  16. 16. Stephen L. Macknik in reply to Stephen L. Macknik 7:18 pm 08/13/2013

    Thank you for your comment, please see the addition made post-hoc to the post, as it may clarify things.

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  17. 17. Stephen L. Macknik in reply to Stephen L. Macknik 7:19 pm 08/13/2013

    Thank you for your comment, see the addition made post-hoc to the post, as it may clarify things.

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  18. 18. Stephen L. Macknik in reply to Stephen L. Macknik 7:20 pm 08/13/2013

    Thank you for your comment, please see the addition made post-hoc.

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  19. 19. Stephen L. Macknik in reply to Stephen L. Macknik 7:20 pm 08/13/2013

    Thank you for your comment, please see the addition to the post made post-hoc, as it may clarify things.

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  20. 20. Stephen L. Macknik in reply to Stephen L. Macknik 7:21 pm 08/13/2013

    Please see addition comment in post. Thanks for your comment.

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  21. 21. Stephen L. Macknik in reply to Stephen L. Macknik 7:21 pm 08/13/2013

    Thanks for your comment. Please see addition comment in post.

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  22. 22. Stephen L. Macknik in reply to Stephen L. Macknik 7:22 pm 08/13/2013

    Thanks for your comment. There are new post-hoc comment s in the post.

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  23. 23. teri eddy 8:12 pm 08/13/2013

    If Time exist past, present, future together. Then free will not only exist; it changes the future instantly and continuously.

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  24. 24. Peter_C 8:46 pm 08/13/2013

    My question is whether the term “free will” has any meaning? I’ve never come across an operational definition of free will. Is there such a definition? If someone has such a definition I would appreciate if they shared it. If all that people mean by “free will” is that some events are randomly determined, or the even weaker, some events cannot be predicted with perfect accuracy, is there anything added by the term “free will”? If free will means something in addition, what is that additional content and how, operationally, how can that special additional component required to turn unpredictable into “free will” be detected? That is, how do I identify free will when I come across it? Does the term “free will” have any meaning beyond being words that we observe certain people use in certain situations particularly when talking about moral culpability? Is “free will”, hence, purely a moralistic label which belongs completely to the “ought” world rather than the “is” world, and, therefore is the concept of “free will” about ethics or moral philosophy and nothing at all to do with the real world? (That is, if one takes the view that moral and ethical theories say nothing substantive about the real world and, instead, that such theories simply systematically place evaluative labels on things like behaviours, individuals, and their decisions.)

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  25. 25. RabbiDan 12:36 am 08/14/2013

    Cool article. 2 points that crossed my mind: 1) The author makes it seem that if God were to know everything that would happen in advance, there can be no free will. The truth is though, if God operates on a level beyond time (as Judaism teaches that He created time & space) , then the fact that he knows what you WILL do is because He sees it AT THE TIME you do it ahead of time. He is not limited in time; so in 1998 He is able to simultaneously watch & know your actions in 2007, WITHOUT having caused them to be. He is merely observing your future FREE WILL. 2)On the other hand, true completely OBJECTIVE free will is very rare. When one chooses a green shirt over a red one, or ketchup over mustard, it was less of him choosing freely and more that the ITEM chose him so to speak. He was already emotionally inclined to choose that thing which he likes

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  26. 26. voice 8:58 am 08/14/2013

    We can only understand a small fraction of the way things are. But I believe that external events are truly random from the standpoint of an observer and the observer can excercise some degree of free will in responding, at least to the external events. Maybe the grass can’t, but we can. If the future is actually unfolding that doesn’t prove that the future is undetermined. It all depends on the nature of time.

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  27. 27. JohnOstrowick 2:16 pm 08/14/2013

    http://johnostrowick.blogspot.com/2011/11/this-debate-amongst-neuroscientists-and.html

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  28. 28. scwarren 7:10 pm 08/14/2013

    Although quantum effects may make the sub-microscopic world non-predictable they introduce only a degree of randomness to the future. We exert no control over quantum events.
    A more serious objection is the fact that both the special and general theories of relativity are incompatible with a flow of time as Einstein and Godel proved in 1949 (Palle Yourgrau – “A World Without Time” – 2005). The half century of embarrassed silence that followed was broken by Julian Barbour’s “The End of Time” (1999), since when it has become mainstream. Without a flow of time there can be no cause and effect and no free will. Since the theories of relativity are unchallenged and no-one has refuted the proof of Einstein and Godel discussions of free will have neither meaning nor value.

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  29. 29. josephrockheart 8:18 pm 08/19/2013

    the only factor unknown is if u will cure the leper, or take away bread from a starving child!!! that is free will = surrender to the thou = be of the survivors (doing good) … so goes the sufi philosophy of the criteria of judgement of man … to do good inspite of having a chance to do evil … the emergent features of the patterns occurring in the brain (in its dynamical form r being mis-understood) … science is the knowledge of how n y things work … the deterministic causation … while religion is the explanation of the humble (surrendered) way of co-habitation … leading to freedom from birth of desires (that r pure illusions leading to chaos n thus lust in the non-fulfillment) n their death … a way of cleansing the mind … in modern parlance = being lean n mean, i can b!!! i will b!!! i will circuit feedback loops to peace, love, bliss n most of all surrender unto The MANIFESTATION = for the thou doth rest in the heart (ghazali says it is the center of thought, the secrets of the heart, book of knowledge, vol ??) … then let the cosmos speak ITS WILL … wilt thou cleanse thy heart sufficiently to hear Reality/Cosmos/God … the thou thee speak??? o peace, blessed b thou o thee!!!!!!!!! :)

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  30. 30. jeanblake80 12:16 pm 01/7/2014

    Free will is the right to make decisions for yourself. You cannot chose the outcomes or be above the laws, but you can make the choice of how you act.
    Jean Blake | http://www.pdceng.com/services/surveying

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  31. 31. August Berkshire 1:57 am 04/24/2014

    From Added Post-Hoc: “For example, executive circuits might set the criterion that memory circuits should recall a politician. Margaret Thatcher might come to mind, because she meets that criterion. But from the exact same initial conditions, Obama might also have come to mind. Which came to mind was a matter of chance. This is not deterministic, because the outcome could have turned out otherwise. But it is also not random, because the outcome had to be a politician.”

    So we get the non-free-will idea that a politician should be recalled. This leads to the non-free-will search of our memories. By chance, due to an indeterminate quantum effect, Thatcher is selected from our limited pool of options (politicians we know).

    We rerun the experiment and, by chance, due to a different indeterminate quantum effect, Obama is selected this time from our limited pool of options (politicians we know).

    So the selection is indeterminate, but since we can’t control that indeterminate quantum effect that led to that selection, free will was not involved. And what difference does the size of the pool of options make?

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