Neuroscience and Free Will: Part 1: Why Neuroscience Poses a Threat to Free Will.
Because I have so much to say on neuroscience and free will, I’ve decided to break this up into a series. I believe it’ll be a two to three part series, but it might be any number of posts. In this first post, I want to face the issue head on, and engage rather than avoid the research that usually allows individuals to declare that we’re not really free at all.
There are few more qualified than Adina Roskies (Ph.D. Neuroscience, Ph.D. Philosophy) to speak on the philosophy of mind, so perhaps I’m getting myself into more than I can handle beginning this series by critiquing her. She has written a lot on free will, and a good part of what she’s written, I agree with. For instance, in her article, “Neuroscientific challenges to free will and responsibility,” (Roskies, 2005) she argues that neuroscience cannot adjudicate this debate–that is, it cannot settle the matter by itself. This is because the notion of free will requires some extra metaphysical ground (such as indeterminism) and the most that neuroscience can show is that our brains seem to be deterministic–as she puts it, neuroscience provides a mechanism for behavior–but it cannot demonstrate determinism on a large scale. At its best, neuroscience cannot verify its assumption on a large scale, but it could suggest that the brain seems to be deterministic.
While Roskies has a lot to say regarding free will (Roskies, 2010a), I want to focus specifically on studies that seem to indicate that we don’t have free will, and so I’ll hone in on the Libet studies, as I believe that those are the biggest threat to free will (and, answering them will also answer other issues around neuroscience and free will).
The neuroscientist/neurosurgeon Benjamin Libet is famous for two sets of experiments, but only one has direct bearing on our discussion here. The study relevant to our topic asked individuals in an experimental group to move their fingers whenever they felt the urge to move and report the time that they decided to move their finger, all while being measured by EEG (Libet, Gleason, Wright, & Pearl, 1983). What this study found was that a barrage of increasing neural activity preceded an individual’s decision to move for hundreds of milliseconds, and that this activity was a consistent and steady stream of activity. It seemed, according to this experiment, that the actions of these individuals were unconsciously initiated and that the individuals did not have any control in initiating them. Libet was quick to point out that these individuals could veto their actions within a critical time period (Libet, 1985), but even this concession only leaves us with “free won’t,” rather than free will.
Roskies (2010b, pp. 14-16), in another article, criticizes this interpretation of Libet’s experiment, claiming that we do not have grounds for claiming that the neural signal preceding the action and the decision to act is actually the neural signal for action initiation rather than the neural signal for volition. However, this interpretation of Libet’s experiment does not work for two reasons: if we needed a neural precursor to decide to act, then either that neural precursor was not free, in which case we don’t have control over our volition, or it was free, in which case it would need a neural precursor, and so on ad infinitum. Moreover, recent evidence from single-neuron recordings has shown that Libet’s neural precursor originates in the supplementary motor area, and that progressive recruitment of neurons starts as early as 1500 ms (one and a half seconds!) before individuals decide to move (Fried, Mukamel, & Kreiman, 2011). There can be little doubt, then, that the neural events preceding one’s decision to move are actually the neural events of action initiation rather than the neural precursor to volition.
Libet’s study has been replicated numerous times, and it has withstood every angle of criticism that it has received over the years (Banks & Pockett, 2007). Libet’s study clearly seems to show that we do not consciously control even the most rudimentary aspects of action initiation.
It is for this reason that neuroscience poses a threat to free will.