Neuroscience of free will, a part of neurophilosophy, is the study of topics related to free will (volition and sense of agency) using neuroscience and the analysis of how findings from such studies may impact the free will debate.
As it has become possible to study the living human brain, researchers have begun to observe decision-making processes. Studies have revealed unexpected things about human agency, moral responsibility, and consciousness in general. One of the pioneering studies in this domain was conducted by Benjamin Libet and colleagues in 1983 and has been the foundation of many studies in the years since. Other studies have attempted to predict participant actions before they make them, explore how we know we are responsible for voluntary movements as opposed to being moved by an external force, or how the role of consciousness in decision-making may differ depending on the type of decision being made.
Philosophers like Daniel Dennett and Alfred Mele consider the language used by researchers. They explain that "free will" means many different things to different people (e.g., some notions of free will posit that free will is compatible with determinism, while others do not). Dennett insists that many important and common conceptions of "free will" are compatible with the emerging evidence from neuroscience.
Overview
The neuroscience of free will encompasses two main fields of study: volition and agency. Volition, the study of voluntary actions, is difficult to define. If human actions are considered as lying along a spectrum based on conscious involvement in initiating the actions, then reflexes would be on one end, and fully voluntary actions would be on the other. How these actions are initiated and consciousness’ role in producing them is a major area of study in volition. Agency is the capacity of an actor to act in a given environment which has been debated since the beginning of philosophy. Within the neuroscience of free will, the sense of agency—the subjective awareness of initiating, executing, and controlling one's volitional actions—is usually what is studied.
One significant finding of modern studies is that a person's brain seems to commit to certain decisions before the person becomes aware of having made them. Researchers have found a delay of about half a second or more (discussed in sections below). With contemporary brain scanning technology, scientists in 2008 were able to predict with 60% accuracy whether 12 subjects would press a button with their left or right hand up to 10 seconds before the subject became aware of having made that choice. These and other findings have led some scientists, like Patrick Haggard, to reject some definitions of "free will".
However, it is very unlikely that a single study could disprove all definitions of free will. Definitions of free will can vary greatly, and each must be considered separately in light of existing empirical evidence. There have also been a number of problems regarding studies of free will. Particularly in earlier studies, research relied on self-reported measures of conscious awareness, but introspective estimates of event timing were found to be biased or inaccurate in some cases. There is no agreed-upon measure of brain activity corresponding to conscious generation of intentions, choices, or decisions, making studying processes related to consciousness difficult. The conclusions drawn from measurements that have been made are also debatable, as they don't necessarily tell, for example, what a sudden dip in the readings represents. Such a dip might have nothing to do with unconscious decision because many other mental processes are going on while performing the task. Although early studies mainly used electroencephalography, more recent studies have used fMRI, single-neuron recordings, and other measures. Researcher Itzhak Fried says that available studies do at least suggest that consciousness comes in a later stage of decision-making than previously expected – challenging any versions of "free will" where intention occurs at the beginning of the human decision process.