Free Will and the Readiness Potential
All healthy humans feel like they have some degree of free will, the ability to discern and consciously choose one of a number of possible options. Free will is here defined as a conscious and deliberate process by which an individual comes to choose between multiple options, absent of any involuntary causal determination. But how does free will fit in with neurophysiology and what we know about the brain?
We know that neurons form networks. The particular connections in and between networks are a result of genetics, biology, environment, and every past experience, action, and thought. We know that our brain is governed by physical law, neurons spontaneously fire when the intra and extra cellular concentrations of NaCl change. All the molecular occurrences in our brains are results of previous ones, and cause future ones. So we can imagine that every thought we have, every action potential, is actually the result of every molecular occurrence since (and including) the Big Bang. Newtonian physics supports the idea that once the initial conditions of the universe were set, the rest of history follows inevitably. This is the central idea of the theory of determinism. If we adopt strict determinism, and imagine a thought experiment in which we possess complete knowledge, of every occurrence, every motion of every particle, every value held by every person, everything they have experienced and thought, we would be able to perfectly predict the outcome of any situation. If we are physical systems subject to determinism, there may not be room for free will in the picture.
Kornhuber, Deecke and Libet have conducted experiments on the temporal relationship between neural activity and conscious awareness, in relation to voluntary action. Kornhuber and Deecke used EEG readings to measure neural activity while subjects flexed their index finger repeatedly. They noticed a shift in cortical potential around 0.5 seconds prior to volitional movement (4) (marked as when motor neuron stimulates the muscle). This shift is called the pre-motor potential or readiness potential (RP).
Libet performed a similar experiment with the addition of a special timer, subjects were told to note the time when they first noticed the urge to act. This addition to be experiment made it possible to compare the relative times at which the RP, the conscious awareness of urge to act, and the action occurred. The RP, in concordance with the results of Kornhuber and Deecke, occurred 0.5 seconds before the actual action (2). The awareness of conscious urge to act occurred 0.2 seconds before the actual action (2). Interestingly, Libet, prior to his work on RP and voluntary action, did work on the perception and awareness of sensory stimuli. In this experiment Libet showed that regardless of the duration of the stimulus, the brain activity it elicits must persist for 0.5 seconds for the subject to become aware of it, even though the stimulus is registered unconsciously after 0.2ms (3).
Neural activity related to a resulting action occurs 0.3 seconds before conscious awareness of the desire to act occurs. This shows that conscious awareness can not be playing a causal role in voluntary action. Libet claims that the results of his experiment do not show that there is no free will involved, his theory and a possible response will be addressed later.
There is a 0.3 second delay between the unconscious registering of a sensory stimulus and conscious awareness of that sensory stimulus (2). There is also a 0.3 second delay between unconscious initiation of voluntary action and conscious awareness that the action has been initiated (3). On top of this we know also that thought, being a property of a physical system cannot be instantaneous. We can now say that our entire conscious experience lags 0.3 seconds behind our unconscious neural experience. The results of experiments performed by Libet, Kornhuber, and Deecke support the absence of “free will” in simple voluntary motion. Now that we know about the prominent research and theories, we can ask how the mechanism of simple voluntary motion, consciousness, and free will could be extrapolated and applied to complex decision making?
Previously we used the theory to account for only simple volitional motor acts, but it can be used to demystify complex decision making as well. The belief that we make complex decisions by consciously processing the information is an illusion, and one of simplicity. We now know that conscious thought is just a delayed representation of the entire decision making process being carried out on an unconscious neural level.
Here is an example of a more complex decision making situation: Josh has decided to quit smoking cigarettes, he is walking down the street and is offered a cigarette, he realizes he is about to reach for it, but does not, recalling a images of cancerous lungs. This is a voluntary action (or voluntary inaction) that is perceived as a conscious decision, much more so than the flicking of a finger is.
I propose that what occurs might look something like this; when he is offered the cigarette two parallel pathways are initiated, one representing accepting, the other rejecting the cigarette. The pathway for accepting the cigarette is reinforced by prior occurrences, habit, and chemical addiction, which is probably why the RP is initiated. The pathway for rejecting it, while less speedy due to its nascence, is the “better” one, it appeals more to his current goals and desire. The inhibitory potential reaches the RP just a few milliseconds before the initiation of action. He is aware that he is about to reach for the cigarette 0.3 seconds after the RP begins, right before it is inhibited, his awareness of his intention to inhibit the action (which may actually occur a couple milliseconds after the action), is mixed with his experience of inhibiting the action.
He is consciously aware of the decision making because it is novel, the pros and cons of each pathway are being compared. Over time and through repetition his reaction in this situation will become more habitual, less novel, faster and less conscious. The acceptance pathway reinforces the RP which will be inhibited repeatedly, the pathway will weaken, until the immediate response is no longer to reach for the cigarette, and he no longer thinks though the decision. The speed and strength of our neuronal networks determines what degree of consciousness we experience. We feel that there is more free will involved in making a complex novel multi step decision, but really it is just that the process being carried out unconsciously is taking a little while, and therefore our (delayed) conscious awareness of it is also quite timely, we feel we are “thinking through” the problem.
The problem I have with Libet is that he claims that his experiment does not disprove free will. He says that free will can still occur by means of conscious vetoing of an intended action. He posits a conscious mental field that cannot be studied by physical means but which can intervene in the physical process of decision making as the element of free will (4). What Libet is saying is that an intention to act is initiated by a RP and governed by physical laws, but an intention to veto is instantaneous and not. Vetoing itself is an act, and a volitional one. The process of almost acting, but not, only makes sense if vetoing an action follows the same process as initiating one. If the veto can be accounted for as part of the physical system responsible for decision making, and no more consciously willed than the RP, we could say that the belief that free will is an illusion has not yet been disproved. We can imagine the unconscious neural timeline as such; at 0seconds the RP begins, at 0.3-0.45seconds the RP is inhibited. We can imagine the conscious timeline as well; at 0.3seconds awareness of intention to act occurs, at 0.6-0.75seconds awareness of intention to inhibit action occurs. This timeline is further illustrated in the previous example story.
I started off wondering if determinism leaves any room for conscious free will. Strict determinism does not. But saying something as simple as humans are physical systems (and only physical systems) leaves no room for free will (in the meaning that it has been used in this paper) either. If a choice has a causal root it cannot truly be free, because freedom requires randomness. Physical systems are causal by nature. Free will can be interpreted in various ways. One way is compatible with the view of humans as only physical systems; that is the idea of free will as the ability of an individual (a causally constrained agent) to make a choice for themselves, free of outside causal factors (a gun to the head).
There is a common conception that if neuroscience could explain and account for everything about the human brain, then everything that makes us unique, innovation, creativity, spirituality, consciousness, will lose its meaning, it will all be reduced to organic chemical reactions. This paper more than ever has made me feel otherwise, I would so much rather be the result of every motion of every particle that has every existed, than be a vague unexplainable “field”.
Web Resource List:
1) http://www.mises.org/story/1943; Lucretius. Does Neuroscience Refute Free Will? Ludwig Von Mises Institute: 10/20/2005
2) http://www.consciousentities.com/libet.htm Libet’s Short Delay. 6/2/2005.
3) http://www.users.globalnet.co.uk/~lka/conz2a.htm#neuroscience; The Neuroscience of Consciousness
4) http://eprints.assc.caltech.edu/167/01/Volition_JCS-Preprint_ASSC_E-Prints.pdf; Gomes, Gilberto. Volition and the Readiness Potential. Journal of Consciousness Studies, 6 (8-9), 1999, pp. 59-76.