My five cents.
Libet-style experiments are about the finding of the readiness potential (RP), which allegedly could predict the outcome of the agent's choice, some time before the agent reported making the choice. Thus the interpretation is that the choice was already made, before the person was aware of it.
The actual relevance of Libet-style experiments is solely due to that interpretation (of RP). But what exactly is RP?
What the Bereitschaftspotential actually meant, however, was anyone’s
guess. Its rising pattern appeared to reflect the dominoes of neural
activity falling one by one on a track toward a person doing
something. Scientists explained the Bereitschaftspotential as the
electrophysiological sign of planning and initiating an action. Baked
into that idea was the implicit assumption that the
Bereitschaftspotential causes that action. The assumption was so
natural, in fact, no one second-guessed it—or tested it.
A Famous Argument Against Free Will Has Been Debunked, The Atlantic
But one aspect of Libet’s results sneaked by largely unchallenged: the
possibility that what he was seeing was accurate, but that his
conclusions were based on an unsound premise. What if the
Bereitschaftspotential didn’t cause actions in the first place? A few
notable studies did suggest this, but they failed to provide any clue
to what the Bereitschaftspotential could be instead. To dismantle such
a powerful idea, someone had to offer a real alternative.
A Famous Argument Against Free Will Has Been Debunked, The Atlantic
In 2012 Aaron Schurger et al made several studies that provided a definite explanation of RP, which not only was confirmed, but at the same time provided an alternative interpretation of Libet-style experiments that made them irrelevant to free will debate by undermining the very premise of the experiment, since now the decision time was compatible with subject's own report time.
As Aaron Schurger, Jacobo Sitt, and Stanislas Dehaene report, “it is
widely assumed that the neural decision to move coincides with the
onset of the RP” (2012, p. E2909). Like Trevena and Miller and myself,
they challenge that assumption. In their view, the brain uses “ongoing
spontaneous fluctuations in neural activity” (p. E2904) – neural
noise, in short – in solving the problem about when to act in
Libet-style studies. A threshold for decision is set, and when such
activity crosses it, a decision is made. They contend that most of the
RP – all but the last 150 to 200 ms or so (p. E2910) – precedes the
decision. In addition to providing evidence for this that comes from
the work of other scientists, Schurger et al. offer evidence of their
own. They use “a leaky stochastic accumulator to model the neural
decision” made about when to move in a Libet-style experiment, and
they report that their model “accounts for the behavioral and [eeg]
data recorded from human subjects performing the task” (p. E2904). The
model also makes a prediction that they confirmed: namely, that when
participants are interrupted with a command to move now (press a
button at once), short response times will be observed primarily in
“trials in which the spontaneous fluctuations happened to be already
close to the threshold” when the command (a click) was given (p.
E2905).
Mele, Free Will and Neuroscience: Decision Times and the Point of No Return
Given these studies and the high implausibility that Libet-style experiments are really relevant to free will debate, since 2012 neuroscientists have refrained from any mention of them. For what is worth, Wikipedia does not even have an entry on Libet experiments, only a passing mentioning on Benjamin Libet's entry.
[..]Schurger appeared to have unearthed a classic scientific mistake,
so subtle that no one had noticed it and no amount of replication
studies could have solved it, unless they started testing for
causality. Now, researchers who questioned Libet and those who
supported him are both shifting away from basing their experiments on
the Bereitschaftspotential. (The few people I found still holding the
traditional view confessed that they had not read Schurger’s 2012
paper.)
A Famous Argument Against Free Will Has Been Debunked, The Atlantic
Is consciousness-the subjective awareness of the sensations,
perceptions, beliefs, desires, and intentions of mental life-a genuine
cause of human action or a mere impotent epiphenomenon accompanying
the brain's physical activity but utterly incapable of making anything
actually happen? This article will review the history and current
status of experiments and commentary related to Libet's influential
paper (Brain 106:623-664, 1983) whose conclusion "that cerebral
initiation even of a spontaneous voluntary act …can and usually does
begin unconsciously" has had a huge effect on debate about the
efficacy of conscious intentions. Early (up to 2008) and more recent
(2008 on) experiments replicating and criticizing Libet's conclusions
and especially his methods will be discussed, focusing especially on
recent observations that the readiness potential (RP) may only be an
"artifact of averaging" and that, when intention is measured using
"tone probes," the onset of intention is found much earlier and often
before the onset of the RP. Based on these findings, Libet's
methodology was flawed and his results are no longer valid reasons for
rejecting Fodor's "good old commonsense belief/desire psychology" that
"my wanting is causally responsible for my reaching.".
Neafsey, Conscious intention and human action: Review of the rise and fall of the readiness potential and Libet's clock
References:
- Aaron Schurger, Jacobo D Sitt, Stanislas Dehaene, An accumulator model for spontaneous neural activity prior to self-initiated movement
- Edward J Neafsey, Conscious intention and human action: Review of the rise and fall of the readiness potential and Libet's clock