Do Rats Have Free Will?

By Neuroskeptic | November 12, 2014 12:11 pm

New research on the neural basis of ‘spontaneous’ actions in rats could shed light on the philosophical mystery that is human ‘free will’.

The study, just published in Nature Neuroscience, is called Neural antecedents of self-initiated actions in secondary motor cortex. It’s from researchers Masayoshi Murakami and colleagues of Portugal’s excellently-named Champalimaud Centre for the Unknown.

The senior author is Zach Mainen, whom I interviewed recently after he helped organize the campaign for reform of Europe’s Human Brain Project.

Murakami et al. trained rats to perform a task requiring patience. In each trial, the rat heard a sound and had to wait in place until a second sound occured. If they waited, they got a large amount of water as a reward. If they moved to get some water too soon, however, they only got a small amount.

Using tiny electrodes implanted in the premotor cortex of the rats’ brains, Murakami et al. discovered that some neurons seemed to act as “integrators” (or counters) – over the course of the waiting period, their firing activity gradually increased. If activity reached a certain threshold before the second sound played, the rat would stop waiting and ‘spontaneously’ decide to go for the small reward.

These “integrator” neurons didn’t always count at the same speed, however. On some trials, they ‘ramped up’ more quickly – and when this happened, the rat was more impatient. This image shows the relationship between ramp up rates and waiting time –


Why did the integrators sometimes count faster than other times? Murakami et al. found a second class of neurons, whose rate of firing (which varied seemingly at random) predicted the rate at which the integrators “counted up”. The authors suggest, therefore, that these latter neurons provide inputs to the neural integrators. When the total amount of input reaches a threshold, a ‘spontaneous’ action is triggered.

What does this have to do with free will? Well, it all goes back to 1983, when a neuroscientist called Benjamin Libet found, using EEG, that a certain pattern of brain activity – a “readiness potential” – occurs in the human brain just before ‘spontaneous’ actions. In fact, this brain event happens even before we are aware of deciding to act.

Libet’s much-discussed finding has been seen as evidence against free will because it seems to suggest that ‘the brain decides to act before we do’.

But what if the readiness potential is somehow the equivalent of the rat “integrator”? That would be a big deal, say Murakami et al. In this case,

activity preceding bound crossing, either input or accumulated activity, could be said to participate causally in the timing of an action, but does not uniquely specify it. The integration-to-bound theory implies that no decision has been made until the bound has been reached… as at any moment up to bound crossing, the arrival of opposing inputs may avert an action.

In other words, maybe the readiness potential is not a consequence of a decision that has already been made, but rather is a contributor to a decision that only happens later.

This is in fact not a new idea. I blogged about this kind of interpretation of the Libet experiment last year, and integrate-to-bound models are quite common in neuroscience (e.g.). However Murakami et al. say that they’re the first researchers to find direct evidence for this model in decision making.

They conclude that the integrator threshold might even reflect the boundary between unconscious and conscious neural processes:

Crossing the threshold from unawareness to awareness [could be] a reflection of bound crossing [in the integrator].

In this way, the integration-to-bound theory may help to resolve the contradiction between the subjective report of free will and the requirement for causal antecedents to non-capricious, willed actions.

…our results provide a starting point for investigating mechanisms underlying concepts such as self, will and intention to act, which might be conserved among mammalian species.

ResearchBlogging.orgMurakami M, Vicente MI, Costa GM, & Mainen ZF (2014). Neural antecedents of self-initiated actions in secondary motor cortex. Nature neuroscience, 17 (11), 1574-82 PMID: 25262496

CATEGORIZED UNDER: animals, EEG, philosophy, select, Top Posts
  • robert barton

    Nothing in this that requires ‘free will’ as a causal explanation, which would commit you to dualism. What is the ‘you’ that is making decisions independently of your brain?

    • Pedro Paulo Oliveira Jr

      which would commit you to dualism

      And that would commit you as dualism-labeller.

    • Hellson

      I agree. Neither is the concept of “free will” necessary to explain these findings, nor is it the simplest explanation for them in any organism, rat or human.

      • Emkay

        hmmm, humans commit suicide..rats wouldn’t even think of it….free will can be deadly…

        • Hellson

          Looking forward to reading all those studies on rats’ thoughts!

  • Felonious Grammar

    It seems to me that “free will” is too sketchy a concept. We do not know the full contents of our minds, so the “free” isn’t so free. The “will”, however seems to me to be related to self-control. Self-control and equanimity, patience, etc., can be learned in order to help with the project of developing a stronger will, but cannot exist as an ideal in decision making. It can also be confounded by all sorts of limitations and conditions such as addiction and a failure to “read” a situation correctly.

    Mice can learn. It seems obvious to me that mice are also sentient, and I have no doubt that they have their own little preferences and personalities and can also learn self-control, equanimity, and patience, in some measure, depending on the mouse and the situation. I suspect decision making and development is more complex and different for wild mice than lab mice. In the “free will” vs. “instinct” equation, environment is everything. And it seems to me that the concept of “free will” when taken as an absolute is an effort to deny the effects of development and environment, which most living things are formed by, and natural limitations.

  • Jan Moren

    “In other words, maybe the readiness potential is not a consequence of a decision that has already been made, but rather is a contributor to a decision that only happens later.”

    What if it’s neither; what if this is the decision being made?

    • Neuroskeptic

      Indeed, although I wonder if that is empirically distinguishable from saying that it’s “a contributor to a decision that only happens later.”?

  • Aaron Schurger

    Murakami and colleagues are not the first to suggest this. See Schurger, Sitt, & Dehaene, PNAS, 2012 “An accumulator model for spontaneous neural activity prior to self-initiated movement” (

    • Neuroskeptic

      Thanks for the comment – and for writing what looks like a very interesting paper!

      Murakami et al. don’t cite your piece, however.

      • Aaron Schurger

        Indeed – I don’t know why they didn’t cite us. Our paper got some media attention and I would have thought that they would have heard about it: Also Jo et al (2013), which you blogged about previously, did cite us, as do a number of other more recent papers.

        • Masayoshi Murakami

          I am really sorry for not citing your paper. It was our mistake not to cite this important paper. We will try to be more careful next time …

          • Aaron Schurger

            No worries. I assumed that you must not have known about our paper. Congratulations for some really outstanding work!

          • Shruti

            I am a big fan of yours, Sir. I love all your novels.

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  • omnist

    The discussion about ‘free will’ is interesting, but it seems to me rather laden in semantic confusion. The problem with scientific methodology is that it cannot resolve this kind of question directly. Conventional science must construct its hypothesis so that a null hypothesis can be disproved, which can never prove the actual hypothesis. But, in tracing back through the logic of the argument, it must always begin with a premise (or set of premises) which themselves are not subject to real proof or even question. The only way to establish premises is by the usefulness or fruitfulness of what is yielded by the inquiry. The real problem surrounding the ‘question’ of ‘free will’ is the notion that this is something which must be challenged at all and thus set up for , falsification by experiment. That would only be true if ‘free will’ is derivative, that is, the result of evolution and development. But, if it is the source of evolution and development, the logical conundrum becomes self-evident: a premise can never be proved, and the causal chain will always result in circularity. At best, one might demonstrate correlation; but “correlation is not causation.” Correlation always suffers a directionality problem. This only arises to begin with because conventional science predicates its inquiry on a paradox: the Universe somehow comes into existence from random, meaningless Accident. So, conventional science harbors an enduring mystery of the ‘miracle’ it never discusses – that is, how does anything orderly, nay, self-organizing and purposeful, arise from random, meaningless Accident, and then persist, contrary to the Second Law of Thermodynamics, not only in maintaining a far-from-equilibrium state, but in evolving to ever higher states of organized complexity, even as entropy is increasing. The alternative perspective would be that ‘reality’ was not an ‘accident’ in the random, meaningless sense to begin with. But, lest anyone fear this suggests ‘theology’, that can mean that there was ‘intention’ without ‘necessity’. Theology usually operates by some argument of determinism, which is also what most conventional science does. That’s the irony. The argument that reality is subject to entropy that will eventually reduce the Universe to either equilibrium or singularity is a fundamentally deterministic point of view, no less that the premise that some Creator God is pulling all the strings. A radically different perspective to both those views is the premise of an ‘intentionality’ that is the source of existence itself, not as an intelligence, but as ‘free will’ lacking intelligence. What computational science shows is that ‘intelligence’ is really quite mechanical, and also is quite distinct from ‘will’ or ‘intention’. That’s why we refer to ‘artificial intelligence’ in computers. What can’t be explained by intelligence at all is the ‘purpose’ behind the ‘programming’ that decides and selects what any form of logic or, more properly, complex process (with frequently paradoxical dynamics) will be directed toward. And, that’s the nature of the problem described in this article. What ‘choice’ ‘will’ be made? That’s not a function of either logic or intelligence or complexity, but of ‘will’. It’s a matter of intention that, I would suggest, can produce existence itself, but in a rather un-god-like fashion. Let’s start with the so-called ‘virtual particle’. This is usually said to arise ‘spontaneously’ in a vacuum from ‘zero-point energy’ (the ‘equilibrium state’ that somehow manifests itself). What results, however, is a particle-antiparticle pair that immediately self-annihilates, leaving behind its energy evidence, but no actual matter. However, if a bunch of such emergent pairs can somehow mutually interfere with each other, to separate particles from their antiparticle alters, then a Universe can be born. That’s one way of describing a Big Bang, although other forms of such creation are possible. This might also be called a quantum foam effect. In any event, to call it an ‘accident’ is a rather arbitrary choice of terms, because why is that an ‘accident’ other than us labeling it an ‘accident’? What if the ‘accident’ is more like what happens all the time on roadways with highly intentional drivers colliding because they are simply ignorant of the intentions of other drivers, all of whom are no less intentional than each other? In other words, localized ‘intention’ can easily produce accidents, but it’s rather more difficult, if not impossible, to explain how localized accidents can produce intentions; yet, the latter absurdity is precisely the premise on which conventional science operates. Why not change the premise? Ignorant, willfulness can in fact emerge and become more intelligent, aware, and even eventually ‘wise’, by rather simple mechanisms. But, no purely accidental system can ever produce ‘intention’ without the ‘intention’ already being present, without some ‘miracle’ happening. I suggest it is far more tenable to assume localized but ignorant intention than to assume localized accidents that either miraculously produce a lawful Universe, or arise from come Creator-God pulling all the strings. The simple premise of ignorant intention can clearly evolve by well-known means. If the only ‘intention’ it has is to effect the means of its own persistence, then every ‘form’ it takes on can be said to literally ’embody’ its ‘learning’ in the physicality of its memory. What physics persistently claims is a symmetry somehow maintained by some kind of interference which prevents self-annihilation. It does not take much to figure out how the laws of physics that we know can in fact be employed in this way – if, and only if, we can ‘explain’ were the ‘will’ to be or exist comes from to begin with. Instead of calling that an accident, why not call it an intention? We don’t need to ‘explain’ will, we need to assume it as the premise, and then see how much we are able to explain by means of that premise. Thus, we also shift what otherwise would be a ‘metaphysical’ problem (after physics) to an ‘antephysical’ premise (before physics). Then, nothing changes in any of validated science, including the experimental results reported on here. But, the implications are profoundly different.

    • Maia

      Thank you, I agree with everything you suggest and admire the way you suggest it. Through orderly questioning. Changing our frame of thought can open up the way we do everything, including scientific investigation, leading to a more deeply creative (and humble) science, and pretty much everything else. Have you read ” Incomplete Nature” by Terrence Deacon? The subtitle: How Mind Emerged From Matter.
      Asking brilliant questions (not giving entertaining answers) dissolves artificial oppositions, and takes the brakes off of discovery. Um, something this magazine is (or should be) very interested in. Actually, it should interest us all, passionately.

      Again thank your for post!

      • omnist

        Thank you. I haven’t read Deacon, but I shall look for it.

    • Emkay

      wow… a 1876 word paragraph….

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  • DisqusThrower

    This topic is above my paygrade. But its my simplistic understanding that neurons evolved from cells that where originally for locomotion. So if muscular systems are synergistic with muscle contracting here and there to create a total effect. Are neurons like that?

    One thing for sure all this “artificial intelligence” talk on tech sites sound like a lot of BS. It seems like anytime a computer can “rub its tummy while patting its head” everyone screams “Skynet!”.

    I’ll shut up now.

    • Emkay

      Good one… I always wondered if the computers (ultimately) that will have artificial intelligence would have the same IQ’s and if some might be bullies, just like the people who create them….

    • Emkay

      Hey Disqus Thrower…help me with Madame George..unreal..

      • DisqusThrower

        Through my travels I’ve learned one thing above all else. That whether in a Bando Gora gangster bar on the outer rim or a Consortium space station’s “swingers club” orbiting Byss at the Deep Galactic Core, and even though it takes the patience of a master Yoda, it is often best to simply…let the Wookie win 😉

        • Emkay

          Remember that ‘awe-inspiring’ moment when the huge black monolith was uncovered (in ‘2001 A Space Odyssey’) on the moon, and it sent a piercing, loud, blinding signal aimed toward JUPITER!
          Well, closer research revealed that the message it sent was a ‘reflection of an engraving on the surface of the monolith, that no one had noticed…
          It said: “Let The Wookie Win”

          Thank you for a great chuckle on a dreary Tuesday…

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  • Cosmic Sky

    Not much of an excuse for them to hurt these poor animals.

    • Elizabeth_Reed

      Thank you! We’re a nightmare of a species, free will or no.

  • Madame George

    Interesting that rats have the power to suspend the laws of the universe in order to make ‘free’ decisions. I think a more accurate article title would be “Rats may feel as if they have free will, much like humans”.

    • Emkay

      Someone wrote ‘everything that humans do comes from the imagination’… I guess that’s true, hmmm, if I think about going to the Publix and buying some food, is that imagination?.. and then when I actually go and get the food, is that free will ?? (cause I could have gone to the Food Lion)…. but I do think millions of dollars and countless academic hours should be wasted on determining the difference, don’t you?

      • Madame George

        Neither of the scenarios you mentioned involve ‘free’ will. Whether you’re imagining, thinking, doing, throwing, sleeping, etc, those choices/actions are determined by underlying forces over which you have zero control.

        Yes, I think neuroscience and, more specifically, the topic of consciousness should be studied vigorously.

        • Emkay

          Wow… first of all you did not pick up on my sarcasm regarding ‘wasting millions of dollars and countless hours’.. pay attention when you read…
          and secondly, you said that “imagining, thinking, doing, throwing?, sleeping, etc, are choices/actions that are determined by underlying forces that we have zero control over…. please tell us what those ‘underlying forces are??

          • Madame George

            I didn’t address your sarcasm because it didn’t warrant mentioning. Your attempt to belittle somebody online by mocking a perceived inability to ‘pay attention’ when reading a poorly thought out retort only further undermines an already futile point you’re trying to make.

            The forces to which I’m referring would be those forces which govern the very small particles in our universe (which, in turn, make up and affect large objects/creatures). So, the strong force and electromagnetic force, primarily.

            To believe in any true notion of ‘free’ will, one must believe that he can suspend the laws of the universe and make a truly independent decision apart from them. This, of course, is entirely impossible. That you or I feel and believe that we have this ability is merely an illusion created by the incredible power of consciousness.

          • Emkay

            “So, the strong force and electromagnetic force, primarily.”

            You say these are the underlying forces that “imagining, thinking, doing, throwing, sleeping, etc, those choices/actions are determined by underlying forces over which you have zero control”

            I am familiar with electromagnetic force, but for some reason I cannot find any references to ‘strong force’. Perhaps you could enlighten us as to a definition or a description of the ‘strong force’.

            Ooops…hey I found something at the Encyclopedia Britannica..”
            Strong force, a fundamental interaction of nature that acts between subatomic particles of matter. The strong force binds quarks together in clusters to make more-familiar subatomic particles, such as protons and neutrons. It also holds together the atomic nucleus and underlies interactions between all particles containing quarks. The strong force originates in a property known as colour. This property, which has no connection with colour in the visual sense of the word, is somewhat analogous to electric charge. Just as electric charge is the source of electromagnetism, or the electromagnetic force, so colour is the source of the strong force. Particles without colour, such as electrons and other leptons, do not “feel” the strong force; particles with colour, principally the quarks, do “feel” the strong force. Quantum chromodynamics, the quantum field theory describing strong interactions, takes its name from this central property of colour.

            Protons and neutrons are examples of baryons, a class of particles that contain three quarks, each with one of three possible values of colour (red, blue, and green). Quarks may also combine with antiquarks (their antiparticles, which have opposite colour) to form mesons, such as pi mesons and K mesons. Baryons and mesons all have a net colour of zero, and it seems that the strong force allows only combinations with zero colour to exist. Attempts to knock out individual quarks, in high-energy particle collisions, for example, result only in the creation of new “colourless” particles, mainly mesons.

            In strong interactions the quarks exchange gluons, the carriers of the strong force. Gluons, like photons (the messenger particles of the electromagnetic force), are massless particles with a whole unit of intrinsic spin. However, unlike photons, which are not electrically charged and therefore do not feel the electromagnetic force, gluons carry colour, which means that they do feel the strong force and can interact among themselves. One result of this difference is that, within its short range (about 10−15 metre, roughly the diameter of a proton or a neutron), the strong force appears to become stronger with distance, unlike the other forces.

            As the distance between two quarks increases, the force between them increases rather as the tension does in a piece of elastic as its two ends are pulled apart. Eventually the elastic will break, yielding two pieces. Something similar happens with quarks, for with sufficient energy it is not one quark but a quark-antiquark pair that is “pulled” from a cluster. Thus, quarks appear always to be locked inside the observable mesons and baryons, a phenomenon known as confinement. At distances comparable to the diameter of a proton, the strong interaction between quarks is about 100 times greater than the electromagnetic interaction. At smaller distances, however, the strong force between quarks becomes weaker, and the quarks begin to behave like independent particles, an effect known as asymptotic freedom.

            So, we have a partial answer to the underlying forces that determine ” imagining, thinking, doing, throwing, sleeping, etc, those choices/actions are determined by underlying forces over which you have zero control.” But I can’t help thinking that ‘biology has something to do with those things…

            Incidentally, Stephen Hawking said ” never trust an atom, they make up everything”..

          • Madame George

            If your conscious agency cannot control the underlying processes which produce thoughts and actions then you cannot claim to have ‘free’ will. If you’re going to quote Stephen Hawking on the topic, here’s something much more apropos:

            Though we feel that we can choose what we do, our understanding of the molecular basis of
            biology shows that biological processes are governed by the laws of physics and chemistry and
            therefore are as determined as the orbits of the planets. Recent experiments in neuroscience
            support the view that it is our physical brain, following the known laws of science, that determines
            our actions, and not some agency that exists outside those laws. For
            example, a study of patients undergoing awake brain surgery found that
            by electrically stimulating the appropriate regions of the brain, one
            could create in the patient the desire to move the hand, arm, or foot,
            or to move the lips and talk. It is hard to imagine how free will can
            operate if our behavior is determined by physical law, so it seems that we are no more than biological machines and that free will is just an illusion.

            -Stephen Hawking and Leonard Mlodinow, The Grand Design, Bantam Books, New York, 2010, p. 32

          • Emkay

            You just said “It is hard to imagine how free will can operate if our behavior is determined by physical law, so it seems that we are no more than biological machines and that free will is just an illusion”.
            Wrong…if one of your ‘biological machines’ decides to use it’s free will and commit suicide, then it also breaks the physical law you mentioned… damn.. what a way to go..

            Oh, the quote about Hawking saying ‘never trust an atom’… I just made that up…
            Please do not reply…lets stop this BSR…

          • Eli

            Research “Matching Law” – our behavior is determined by the amount of reinforcement we have received in the past for such behavior; i.e. learning. Our genes determine the interplay between what may or may not be as reinforcing. We “learn” to respond in certain ways to certain stimuli, and as complex individuals, are faced with countless stimuli and reinforced behaviors throughout our day. The likelihood we do anything is determined by the extent it has been reinforced in the past, (or associated behaviors to associated stimuli; e.g. I may have never eaten a new food but I have been reinforced for eating similar food or have followed similar rules such as it being described as “sweet” and I have in the past enjoyed sweet food).

            So in a nutshell, people are as likely to comment as similar behavior has been reinforced in the past. Our view of choices as having freely been chosen is merely a reflection of our ignorance with regard to our history of reinforcement, and the complexity of the current schedules or reinforcement (is this chair comfortable, am I hungry, do I have to pee, do I feel the need to communicate further, etc.) operating at any given moment.

          • Emkay

            of course…..

  • ejhaskins

    So, those of you who deny our ‘free will’ think that none of us could have avoided responding here?

    • Emkay

      Correct! and thank you for not responding…

  • johnmerryman

    Isn’t the notion of free will something of an oxymoron? To will is to determine.
    I think the deeper issue is our subjective sense of time as a progression from a determined past into a probabilistic future and the assumption that since the laws of nature seem fairly deterministic, otherwise they wouldn’t be laws, the future must ultimately be as determined as the past and thus everything, not just human actions, is determined. The underlying reality of time is that it is change which turns future into past. Tomorrow becomes yesterday. Probability precedes actuality. So since information can only travel at finite speeds, the input into any event only arrives with its occurrence, so even if the laws determining the outcome are set, the input is not. We are very much part of that process and affect our context, as it affects us, so we are part of that process of determination. It is only the hindsight of constructed narrative which makes it all seem to fit together so neatly.

    • Emkay

      Grandaddy always said “the only thing that is truly permanent is change”…

  • jim birch

    So we have free will, but only for the nanosecond between reaching the readiness potential and the decision popping out. It’s better than nothing I guess…

  • Doc

    Of course rats have free will – that’s why they choose to run for Congress

    • Emkay


  • airvine

    This and other Libet inspired experiments make conclusions based upon
    their measurements of a tiny fraction of the activity in a brain that
    led to the “decision”. A decision process, embodied in a huge complex
    network of neurons in the brain can, and probably does just result from a
    brain’s complex stored decision making process, i.e. lots
    “subprograms” or “subroutines” built up over years.of experience and learning. Exercising “free will” is never a “decision” standing independent of everything that brain has experienced prior to that “decision” and “decided” to incorporate in its decision making processes.

    • Emkay

      “Using tiny electrodes implanted in the premotor cortex of the rats’ brains”

      If those electrodes are not in the EXACT place in each of the ‘rats brains’ then the compiled results are null. A single millimeter off, up, down, or sideways would give a different measurement… this article is laughable…

      • airvine

        And there is no reason to to believe that anyone can define the term “exact place” in any meaningful way. All of these measurements are made of from 1 to an immense (e.g. a few million) collection of electrons many of which have grown (“plasticity”) as a result of an individual brain’s experiences.

        • donc

          This comment is nonsense. The authors recorded single units (single cells) and did pretty careful anatomy to assign their recording sites to the brain region of interest. Of couse, you can define meaningful places in the rat brain:

          • airvine

            Pardon my typographical error I meant “neurons” not “electrons”!
            I think that in your view, If I say that I have measured the temperature of a randomly selected dining table top in a randomly selected coffee house in10 cities in the US, I can say that I measured a temperature at the “exact same place” in each of those cities.

  • Angela A Stanton, Ph.D.

    This sounds very much like quorum sensing to me in which a certain threshold reached that will override all actions to chose the then dominant ultimate “bets” choice. I believe the rat had no free will at all. There is also an allele associated with impulsive actions. That gene allele predisposes each test subject differently. This research said very little to me.

  • myActualViews88

    These comments show the world how ridiculous free-will believers really are.

    This article doesn’t support the existence of free-will in anyway, it merely shows us different behaviors in neurons, it doesn’t tell us that the rats control anything or have any free-will.

    How can the people who believe in free-will also believe in evolution?

    If every time there was some gap or unknown in evolution journalists came out publishing articles saying “evolution is not true after all” what would people think?

    On the other hand every time there’s something new in behavior or neuroscience there’s some article by journalists “free-will some how exists”…wtf?

    The evidence supporting evolution is much weaker than the evidence telling us that free-will is non-existent…and also evolution relies upon assuming that determinism is true.



No brain. No gain.

About Neuroskeptic

Neuroskeptic is a British neuroscientist who takes a skeptical look at his own field, and beyond. His blog offers a look at the latest developments in neuroscience, psychiatry and psychology through a critical lens.


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