Action fluency and conscious intention: being aware of what we are about to do.

In our daily life, we have the frequent experience of willing and initiating voluntary actions, which we here term “volition.” The nature of volition, however, remains poorly understood, and the very coherence of the concept is controversial (; ). Experimental psychologists have attempted to investigate volition scientifically, but the lack of any consensus definition has limited progress (; ; ; ; ; ). proposed a cluster definition, involving a set of features that jointly contribute to making an action volitional: (i) the agent is conscious of their action, (ii) the action is innovative or spontaneous, (iii) the action has no immediate external trigger, (iv) the action is goal-directed, or reasons-responsive. Most neuroscientific studies have focussed on just one of these aspects (eg ; ), and few studies have addressed them in combination. The recent experimental study of volition arguably began with the work of . In their experiment, participants were asked to make voluntary hand movements spontaneously when looking at a rotating dot on the screen, while brain activity was recorded by electroencephalography (EEG). After a movement was made, the clock then stopped in a random position, and participants reported the time at which they experienced the intention to act (“the time of appearance of their urge to move” in Libet’s words). The clock provides an estimate of the time of conscious intention (“W time”). W time was approximately 200 ms before action onset, while the beginning of the EEG readiness potential (RP), a common precursor of voluntary action, occurred some 300 ms before that in Libet’s data. Taking the onset of the RP as a marker of the brain initiating the action (), Libet argued that these results showed that voluntary actions may be initiated unconsciously. While Libet’s results opened the path to experimental studies of volition, they also attracted lasting controversy. These discussions generally hinge on methodological difficulties in (i) eliciting truly voluntary behaviors in such experiments, and (ii) measuring the conscious experience relating to these behaviors, and, more recently, (iii) interpreting the relation between action-locked RPs and the conscious initiation of action (). We now discuss these in order.