Neuroscience and Free Will: Part 2: Why Neuroscientific Critiques of Free Will Appear Methodologically Unsound.
In part two of this series, I will discuss the methodological problems with studies such as Libet’s and show that there are alternative ways to interpret the data. It’ll be part three before I sketch an account of a neuroscientific concept of free will, and part four before I offer any positive data for it.
Studies in the vein of Libet et al. do seem to pose a problem for free will. However, there is good reason to believe that–upon closer inspection–they are not methodologically sound. The first strong hints of this came in 2010, when a study surfaced that in the Libet paradigm, not only is there a readiness-potential (RP) before a conscious decision to move, there is also a RP before a conscious decision to not move (Trevena & Miller, 2010). This seems to indicate that this RP is not an unconscious neural determinate of a voluntary action–that there might be something in the experimental paradigm responsible for the RP rather than unconscious neural activity. Another two experiments by Miller, Shepherdson, and Trevena (2011) furnished further support for that idea. In their article, Miller et al. demonstrate through their two experiments–each with two conditions–that the cognitive activity of monitoring a clock seems to be responsible for the RP’s occurrence. They found that in each of the two experiments, a condition where participants had to monitor a clock to report the time of their action, there was a RP before the action, but that RP was absent in conditions without the presence of a clock–indicating that these actions may have truly been self-chosen. This result–that cognitive activity of monitoring a clock or attending to an action in time–finds support from a very similar study, that showed that actions where the timing was unattended lacked an early-stage RP (Baker, Mattingley, Chambers, & Cunnington, 2011). These studies seem to show that cognitive processes heavily influence the RP, and that it is likely not neural activity of a chosen action before conscious awareness of that choice, but due to other cognitive factors related to the experiment. More research needs to be done in this area, but with three experiments indicating that the Libet study and experiments like it may be methodologically flawed by not accounting for cognitive factors specifically related to the experimental paradigm, there is enough reason to maintain skepticism for the claim that these studies have shown that choices arise prior to conscious will.
A quick reference to another two studies similar to Libet-type studies is necessary here, because the methodological issues that apply to Libet-type studies do not at first appear to apply to these other studies. Soon, Brass, Heinze, and Haynes (2008) performed an experiment that appeared to show that there exists a neural determinate of an action up to 7 to 10 seconds before an action is consciously chosen. This study was also replicated (Bode et al., 2011). These studies analyzed fMRI data with highly complex algorithms, and these algorithms were able to predict from the fMRI whether a response would be a right or left response 7 to 10 seconds before the response was consciously chosen with up to 57% (in the Bode study) or 60% (in the Soon study). However, a recent study has shown that these studies may have been flawed also because of cognitive factors (Lages & Jaworska, 2012). Lages and Jaworska note that most untrained individuals have an extremely difficult time creating truly random sequences, and the algorithms may have simply picked up neural markers of either intending to maintain or intending to switch responses. Indeed, using a purely behavioral version of the same experimental paradigm with the same inclusion criteria, Lages and Jaworska were able to predict with 61.6% accuracy–higher than that of either Soon’s study or Bode’s–the actions of participants before they made them. The studies of Soon et al. and Bode et al. thus seem to ignore cognitive factors related to whether or not a participant intended to respond in a certain way.
More research is clearly necessary in this area. However, given the methodological problems that appear to exist in neuroscientific studies purported to show that free will is an illusion, there is good reason to hold this purported claim in an air of skepticism–especially when there is strong evidence that we can choose our own actions (in part four, to come).