Part III: Threats to free will from neuroscience

Compatibilists think that we are morally responsible for our actions even if we inhabit a deterministic universe. They argue that moral responsibility does not require magic powers (i.e. the unconditional ability to do otherwise), but instead, requires that an agent possesses certain psychological capacities C (e.g. rational deliberation, self-control, mental time travel) and that those capacities are not constrained by any excessive internal (e.g. strong addictive desires) or external forces (e.g. being held at gunpoint). If we are to understand ‘free will’ as a placeholder for whatever gives us moral responsibility, compatibilists would argue that the unconstrained exercise of our psychological capacities is an exercise of free will.

On this view, free will is not just an all-or-nothing feature, it also comes in degrees. Worms don’t have free will, children have some, and psychologically normal adult humans have quite a bit of free will, at least some of the time. Very young children (1-2 years old) don't have free will because their psychological capacities aren't sufficiently developed. Psychopathic adults don't have as much free will as normal adults because their psychological capacities are impaired. The extent to which normal adult humans have free will—in this compatibilist sense—is a matter of controversy. There are many scientists who think that recent findings undermine our belief in free will. That is to say, they believe that the real causes of our actions are something other than what we think they are (e.g. unconscious processes, environmental factors, brain chemistry). Before reviewing those findings, it might be useful to consider a range of hypotheses one could formulate regarding the extent to which we have free will:

1) Streams of freedom: C regularly causes our behavior.
2) Flickers of freedom: C rarely causes our behavior.
3) Zero freedom: C never causes our behavior.

I do not take these three hypotheses to be exhaustive, by any means, but only useful in illustrating the debate among philosophers and scientists. I suspect most of the population would endorse something pretty close to 1. Free will skeptics hold that 3 is true and will often cite brain imaging studies for support (e.g. Libet 1983, Soon et al. 2008). These studies are taken to show that unconscious processes—processes for which we are not, and cannot be aware of—drives our behavior. If unconscious processes are the sole causes of our behavior, then our conscious processes don’t cause our actions, even if we may think that they do. I will now briefly summarize the basic methodology of such experiments.

Subjects are hooked up to electrodes are asked to make a simple decision without thinking about their reasons for doing so. For example, deciding between flexing their left or right wrist. The subjects are also told to carefully monitor a fast moving clock to determine when exactly they came to their random decision. Afterwards, the experiments compare the time to which the subjects reported their intention to act, to the electrical activity in their brain.

Across a number of experiments, EEG data show increased brain activity in the motor cortex 300ms before the subjects report their intentions. The brain activity that precedes the conscious decision is taken to demonstrate that the subjects’ decision making is carried out by unconscious or random brain processes, rather than by the subjects themselves. Scientists then make the following inference. These findings generalize to all of our decisions. Thus, these experiments demonstrate that we don’t ever actually have free will.

I believe that the scientists and philosophers who cite these kinds of studies in support of free will skepticism make a hasty generalization. The conclusions of the experimenters may be good explanations for what’s going on in these specific experiments, but how much application do they have in the real world? After all, there is at least some reason to think that a subset of our decisions and actions aren’t based on random or unknown processes for which we are unaware. Surely they sometimes involve conscious reasoning, carefully weighing the pros and cons of a tough decision. For example, whether or not we should have kids, which career to pursue, and which conclusions we ought to draw from neuroscientific studies. Free will skeptics would of course deny these claims, but the burden of proof is on them to demonstrate that their generalizations hold true. 

One might argue that our decision making processes still interact with brain processes for which we are unaware. Surely unconscious processes are going to interact with our conscious ones, but it doesn’t follow that our conscious processes never cause us to do anything. If an unconscious process can cause behavior, why couldn’t a conscious one as well? Many of the claims regarding causation involve implicit assumptions about the nature of causality. Thus, scientists and philosophers are not only making claims about the details of the experiments, they are also making claims about metaphysics. There is much more to say about causation and its relation to mental phenomena, but it would be more suited for a post of its own.

In conclusion, compatibilist free will would be threatened only if the findings in these experiments really did generalize to all of our actions. If our conscious thoughts never gave rise to action, then we would not have free will. At this point, such a conclusion is unwarranted, to say the least. In the next post, I will discuss another possible threat to compatibilist free will. Namely, findings in the field of social psychology that are taken to show that our behavior is determined by situational factors that we are unaware of.

Works cited

Libet, B., Gleason, C. A., Wright, E. W., & Pearl, D. K. (1983). Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). Brain, 106(3), 623-642.

Soon, C. S., Brass, M., Heinze, H. J., & Haynes, J. D. (2008). Unconscious determinants of free decisions in the human brain. Nature neuroscience, 11(5), 543-545.


*This post is part of a series on free will.