By April Cashin-Garbutt, MA (Cantab)

The question of whether we have free will has plagued philosophers for centuries. Recognising that neuronal activity lies at the root of all cognitive function, are we fully in control of our own actions, or is free will just an illusion? To seek answers to these questions, I spoke with leading neuroscientists and asked them to share their personal views.

Yes, we do have free will

• “I think we do have free will and it is not a uniquely human thing as I think many species do. People can often act in ways that are not adaptive. We are not like machine-learning, which always generates the best possible outcome, sometimes we do things that are not optimal and so there must be some other thing going on.” Professor Sheena Josselyn, Neurosciences & Mental Health program at The Hospital for Sick Children (SickKids)


• “Yes I absolutely think we have free will but I think it is an entirely human social construct. Our brain restricts the behaviours that we can and are likely to execute under certain environmental conditions, so it is not completely pre-determined. The fact that we do not ask children or mentally ill people to be entirely responsible for their actions, implies that free will is a social construct. There is not much difference between a 17 and 18 year old’s brain, for example, but we treat them totally differently when they commit a crime.
  
  I believe our behaviours are more highly constrained than we would usually like to admit. But I also think there is a social imperative in an open society to insist that people have free will, as a way to encourage individuals to be responsible for their actions.” Dr Cornelius Gross, Group Leader, Senior Scientist, and Deputy Head of the Epigenetics & Neurobiology Unit at the European Molecular Biology Laboratory (EMBL)


• “Of course we have free will! We subjectively experience free will, there is no doubt about that. Free will doesn’t have a different status to other things that you are aware of, such as whether you see colours. All of these things you think about are things in your head, they are all just thoughts and ideas in your head and so I don’t view free will as having a special status.
  
  My perception of colour is a thought in my head, it is supported by the world, but when I look at an object and see a colour, that’s all because of the way I process information and the perceptual state, which is something I construct and so I experience that, so it is real for me. In the same way free will is an experience and it is real. I think to deny that you experience free will is odd!” Professor Rich Krauzlis, National Eye Institute


• “I do think we have free will as we are obviously more than a set of our reflexes and internal models. Ultimately, we are defined by what we say and do—rather than what happens to us. We have the ability to adapt our responses to ‘externally generated’ stimuli – and this is key to our subjective awareness that we control our own volitional actions in the world.” Dr. Kathleen Cullen, Professor in Biomedical Engineering, Johns Hopkins University and co-director of the Johns Hopkins Center for Hearing and Balance


• “Yes we do have free will. Our brains are ours. The brain is who we are, so yes we are controlled by our brain but that is just saying you are controlled by yourself. In that sense, the will is yours, so you are free to have it.” Associate Professor Dayu Lin, NYU Langone 


• “Yes, and the emphasis is on the ‘we’. An organism experiences its brain activity as ‘I’ from the perspective that I have free will. I am probably more predictable than I'd like to be, but I don't think it boils down to quantum physics, it boils down to an understanding of how come all that brain activity comes together to form the ‘I’ we experience as individuals.” Professor Adam Kepecs, Cold Spring Harbor Laboratory


• “Yes I do think we have free will. One reason why people think we don't have a free will is that experiments on humans have shown activity in brain circuits even before the person makes a decision. However, just because you can't articulate a decision doesn't mean that you didn't make it.” Dr Sabine Krabbe, Janelia


• “Yes I think we have free will as we are we are free to decide whatever we want and you can see people take lots of different decisions. I think if we feel trapped in a situation, it's more our own mental scheme that trap us more than being able to decide.” Graziana Gatto, Salk Institute


• “I think we do have free will. The alternative to free will is that everything is deterministic. But I think there’s enough stochastic elements to processes such as neurotransmission that it can't be fully deterministic.
  
  To say that free will is based upon the fact that things are random, is dry and it is very theoretical as well, but at least it says that it's not fully deterministic.
  
  We're shaped by so many experiences and sensory stimuli that being able to predict what someone else will do, even if we were to fully understand their nervous system, would still be nearly impossible.
  
  In a sense, the fact that we can't fully predict someone's behaviour or function I think is evidence for free will.” Dr Tuan Bui, Assistant Professor, University of Ottawa


• “I think we do have free will because I think the complexity of the world we live in is so great that we will never have the practical ability to predict behaviour, meaning that for all practical purposes we do have free will.” Professor Larry Swanson, University of Southern California


• “Yes we do. It is a good question because if we can predict how we move and so forth, then how much freedom do we really have? I think an important point is that we don’t interact with the environment in a fixed way. For example, given a stimulus, our response is not necessarily the same.
  
  I don’t think that it will ever be the case that, even knowing all the variables, we will be able to always accurately predict what the response will be and I think that the accuracy of this prediction is the extent of our free will.
  
  The question is where does free will come from? I think it is made in the structure of the brain and the fact that it is a complex system in the sense that the interactions of the parts makes new properties that emerge that are not necessarily within the parts themselves.
  
  If you think about the number of different ways neurons can connect and interact, it is probably something larger than anything else in the universe and that’s the range of our free will.” Dr. Marco Tripodi, Group Leader, MRC Laboratory of Molecular Biology (LMB)


• “I'd like to believe I have free will and that I am the author of my actions and my life. At least it feels like this to me and I like it even if one day it turns out to be just an illusion. 
  
  As a psychiatrist I often see patients in whom free will appears to be compromised by brain disease. I am thinking for example about severely ill patients with delirium or acute psychosis and that because of the disease these patients seem less free than others, which has obvious legal ramifications in my daily clinical practice. However, most importantly, when we treat the disease, free will is fully restored. So, there is a graduation of free will and the basis of free will is certainly the brain. Some brain areas like the prefrontal cortex seem to be more important for free will than others such as cerebellum, and perhaps one day we may even find specific free will neurons.” Dr Marc Aurel Busche, Harvard Medical School & Massachusetts General Hospital


• “I'm amazed at how much of our control over behaviour, and things that feel voluntary, may well be implicit and outside of conscious control. You might therefore conclude that we do not have the capacity to deliberate, and choose actions, and things like this, however, I don't think that is the case, or at least I'm not willing to admit it yet! I'm going to hold on to free will for a while.” Dr Josh Dudman, Janelia

No, we don’t have free will

• “We do not have free will. I have always believed we are a victim of our own biology. There is no ghost in the machine here that is pushing all the levers, free will is an illusion. This is something I am very comfortable with.” Professor Michael Long, NYU School of Medicine


• “I don't think we have free will as I think we are constantly receptive to either our sensory environment or our internal biases or priors and we are not shielded from a lot of the things that we are taking in, some of which we may not even be aware of.
  
  There are a lot of psychology experiments where you can let the subject do activities and then, later on, they will be more receptive to certain things. To that extent, I think we are constantly under influence of social and environmental input and so maybe it is more of an illusion that we have free will.” Dr Nuo Li, Baylor College of Medicine


• “Mostly no. A really minimal example of a system that can take actions on the world, is a thermostat. A thermostat has a set point, basically a goal in life which it didn't decide; it can perceive the world and it takes actions in order to get to its goal. Thermostats can also affect the world.
  
  I think, in some sense, people are like thermostats with a lot of bells and whistles when it comes to the question of control itself. We have a lot more objectives, we have much more sophisticated perception, and we have to abstract away a lot of the explicit mechanism of the action we take on the world and things we perceive, but I guess I think that that's more on the side of consciousness and what it's like to be control theoretic system, rather than a question of if our will is free.
  
  But your decisions aren't really free in the sense that I think people often mean it. I think that to be truly free requires the introduction of another element that I wouldn't know what to call.
  
  However, it depends how you define free will -- I think the most generous definition of free will would just be the subjective experience of being a system that can take actions that affect the world, so in that case, if a thermostat has free will, we have free will!” Kim Stachenfeld, PhD, Research Scientist, DeepMind


• “I think free will is an illusion, but we will never have the sensation of not having free will.” Andrea Hasenstaub, PhD, is an Assistant Professor in the Coleman Memorial Laboratories in the Department of Otolaryngology-Head and Neck Surgery (OHNS) at the University of California, San Francisco

It’s complicated!

• “To say we don’t have free will would be too big a leap from our relatively limited understanding of how the brain works. 
  
  Part of what makes science challenging but also useful for society and human progress is that scientists focus on questions for which we can find very rigorous and very clear answers. And I think some questions, like free will, will eventually pass to that regime, but I can't think at the moment of how I would do a single experiment that would show definitively that there is or is there is not free will. Until we get to that point, I think the question remains with philosophers.” James Fitzgerald, Ph.D., Group Leader at Janelia


• “I appreciate that some psychologists say that free will is an illusion. As a neuroscientist, I would like to understand whether the molecules and machinery of the brain can explain all our behaviours, including perception and subjective feelings. If all our behaviour is determined by these materials, one could say there is no free will and perhaps we are just monitoring what happened, but I'm open to other views!” Professor Naoshige Uchida, Harvard University


• “It depends how you define free will! But yes, I think we have free will in the sense that you can activate neurons in a mouse optogenetically to compel the animal to be hungry, but there are still choices that the mouse could make within this state. We have all these different drives tugging at us all the time, so we always have some control in a sense, as you are consciously avoiding doing lots of things all the time while choosing to do others. 
  
  Still, it is hard for me to answer this question as free will is often complicated by consciousness. Although we make choices all the time, to experience them as “free” we have to experience them consciously. In humans, conscious experience is usually verbally mediated through our internal monologue, so this further complicates these distinctions.” Dr Yoav Livneh, Harvard Medical School


• “I think we are a combination of our genes, which reflect an evolutionary form of memory, and our experiences coupled with some randomness and I think that creates a form of complexity that is awe-inspiring. Most people would probably say this translates to us not having free will, but I think there is something incredibly compelling to account for how we do what we do, which is amazing, given that all we are is genes and past experience.” Associate Professor Nicole Rust, University of Pennsylvania


• “I don't know whether we have free will or not. What I do know is that, as humans, we have a surprising amount of individuality and a substantial amount of that individuality comes from our genomes. I think an understudied and underappreciated problem in neurobiology is how that individuality, the uniqueness of each one of our genomes, and the uniqueness of our experiences, translates into differences in brain activity and behaviour.” Dr Sandeep Robert Datta, Harvard Medical School


• “We’re certainly not computers as we’re not deterministic. Given the exact same input, a computer will do the same thing every time, but we won’t. However, in some ways we are like a machine as we are bound by certain constraints. There are things that we won’t sense and there are things that exist that we won’t know are there. I think we have free will within a certain space, but that space is limited. Life and biology is based on a set of systems, our brains, our hearts, our lungs all work in a certain way and it doesn’t just work. With any system, there are things that it can do and things that it can’t, so I think we cannot do or think anything we want, but we are not just a machine in the sense that we follow some programme that we can’t break out of.” Dr Gabe Murphy, Allen Institute


• “Our models about the world and ourselves are sensory driven, meaning that they come from sensory experiences of our life. Thus the models form uniquely for every person because the experience sets are different and the intrinsic circuitries are different. 
  
  Is that free will? Well it comes from how the circuitry of the brain incorporates experiences I've had and that gives me a unique filter. I think that unique filter could be seen as free will. That is, given the same stimulus, I will process it differently than you and given the same set of decisions, I will make a different decision because I have a different model base. 
  
  The model base arises in part from my genetics and part from my experiences, therefore I'll come up with a unique solution to the impression again and I think we can call that free will.” Dr Adam Hantman, Janelia


• “I think we're built to have a preferred way of doing things and much of our behaviour is automated, so I think certain things we don't have any free will over, but I think there are other facets that we do. 
  
  So it seems like we're pre-programmed to feel and do certain things, and others we have more flexibility with. I think we have a framework within which we can work.” Dr Randall Platt, Professur Biologisches Engineering, ETH Zurich


• “I remember the very first time that I was a subject in a classical conditioning experiment. I didn’t know anything about the task I was about to undertake and I was asked to watch a movie. During the film, they were presenting some stimulus and puffing me in the eye and I learned to blink and predict when the air puff was coming.
  
  After the experiment, they asked whether I heard the pre-emptive tone and I knew that there had been an annoying noise but I wasn’t consciously aware that the tone was there to allow me to make blinks in anticipation of the puff coming. So it wasn’t that I was deciding to blink out of free will. 
  
  What's interesting is that, if you experience a classical conditioning paradigm, even if somebody asks you not to blink when you hear the tone, you cannot help it. So even if my will in this instance was not to blink, I still blinked and so I think maybe we don’t always have free will.” Professor Javier Medina, Baylor College of Medicine