- seCtIon tHRee: BoDY AnD WoRLD
One way of investigating the experience of exercising conscious will is to ask what
it feels like to have an urge to act. This may be in response to a sensory event like
the tickle on your nose that you’re longing to scratch, or a part of a pathology
like Tourette’s syndrome, which can involve swearing uncontrollably. Studies have
investigated the neural correlates of both urges and suppression of urges, but it
is hard to separate the urge from its inhibition, since prolonging the urge by defi-
nition means resisting it. You can also distinguish between the what, the when,
and the whether aspects of intentional choice (Figure 9.2, and Brass et al., 2013).
Designing brain-imaging experiments that target only intentional action is difficult.
In ‘free-choice’ scenarios with numerous trials, participants are usually instructed
not to act stereotypically (e.g. not to simply alternate between responses) – that
is, they are implicitly given a randomness instruction. In some studies (e.g. Soon
et al., 2008), they are specifically asked not to make button selections in any kind
of pattern. Parts of the fronto-parietal network might be involved in this strategic
aspect of the tasks, by helping track the sequence of responses across trials in
working memory (Lau et al., 2004a), even though this is not what is meant to be
being tested. Another approach is to ask people to attend either to their intention
to act, or to the action itself. One study (Lau et al., 2004b) found that attending
to the intention led to stronger activation of the preSMA, supporting the ‘shared
circuit view’ that the same areas are involved in objective control and the subjec-
tive experience of control. In contrast, however, in one of the rare experiments in
which participants could choose between multiple options (by choosing what
number to add to a systematic or unsystematic sequence), no overlap was found
between areas thought to be involved in intentional choice and those correlated
with participants’ reports of feeling more freedom to choose (Filevich et al., 2013).But the real problem for our purposes here is not just that isolating the neural
correlates of ‘free will itself ’ is fiendishly hard. It is the problem we keep coming up
against in different guises: that having motivations and making decisions doesn’t
feel like neurons firing, whether in the SMA, DLPFC, or anywhere else. It feels as
though there is something else – me, my own mind, my consciousness – that
makes me free to act the way I want.THE HALF-SECOND DELAY
IN CONSCIOUSNESS
One of the most important questions to ask when it comes to the relationship
between consciousness and voluntary action concerns timing. Does conscious-
ness come early enough in the sequence of physical events that leads to an action
to be able to exert a causal effect of its own?
To tackle this question, we need to go back to the late 1950s, when American
neuroscientist Benjamin Libet began a series of experiments which led to the
conclusion that about half a second of continuous neuronal activity is required
for consciousness. This became popularly known as Libet’s half-second delay
(Nørretranders, 1998; McCrone, 1999). The issues raised are fascinating, and there
have been many arguments over the interpretation of the results, so it is worth
considering these studies in some detail.