Libet's legacy: A primer to the neuroscience of volition.

The neuroscience of volition is an emerging subfield of the brain sciences, with hundreds of papers on the role of consciousness in action formation published each year. This makes the state-of-the-art in the discipline poorly accessible to newcomers and difficult to follow even for experts in the field. Here we provide a comprehensive summary of research in this field since its inception that will be useful to both groups. We also discuss important ideas that have received little coverage in the literature so far. We systematically reviewed a set of 2220 publications, with detailed consideration of almost 500 of the most relevant papers. We provide a thorough introduction to the seminal work of Benjamin Libet from the 1960s to 1980s. We also discuss common criticisms of Libet's method, including temporal introspection, the interpretation of the assumed physiological correlates of volition, and various conceptual issues. We conclude with recent advances and potential future directions in the field, highlighting modern methodological approaches to volition, as well as important recent findings.

What is the intention to move and when does it occur?

In 1983 Benjamin Libet and colleagues published a paper apparently challenging the view that the conscious intention to move precedes the brain's preparation for movement. The experiment initiated debates about the nature of intention, the neurophysiology of movement, and philosophical and legal understanding of free will and moral responsibility. Here we review the concept of "conscious intention" and attempts to measure its timing. Scalp electroencephalographic activity prior to movement, the Bereitschaftspotential, clearly begins prior to the reported onset of conscious intent. However, the interpretation of this finding remains controversial. Numerous studies show that the Libet method for determining intent, W time, is not accurate and may be misleading. We conclude that intention has many different aspects, and although we now understand much more about how the brain makes movements, identifying the time of conscious intention is still elusive.

Why neuroscience does not disprove free will.

While the question whether free will exists or not has concerned philosophers for centuries, empirical research on this question is relatively young. About 35 years ago Benjamin Libet designed an experiment that challenged the common intuition of free will, namely that conscious intentions are causally efficacious. Libet demonstrated that conscious intentions are preceded by a specific pattern of brain activation, suggesting that unconscious processes determine our decisions and we are only retrospectively informed about these decisions. Libet-style experiments have ever since dominated the discourse about the existence of free will and have found their way into the public media. Here we review the most important challenges to the common interpretation of Libet-style tasks and argue that the common interpretation is questionable. Brain activity preceding conscious decisions reflects the decision process rather than its outcome. Furthermore, the decision process is configured by conditional intentions that participants form at the beginning of the experiment. We conclude that Libet-style tasks do not provide a serious challenge to our intuition of free will.

Ordinary people think free will is a lack of constraint, not the presence of a soul.

Four experiments supported the hypothesis that ordinary people understand free will as meaning unconstrained choice, not having a soul. People consistently rated free will as being high unless reduced by internal constraints (i.e., things that impaired people's mental abilities to make choices) or external constraints (i.e., situations that hampered people's abilities to choose and act as they desired). Scientific paradigms that have been argued to disprove free will were seen as reducing, but usually not eliminating free will, and the reductions were because of constrained conscious choice. We replicated findings that a minority of people think lacking a soul reduces free will. These reductions in perceived free will were fully explained by reductions in people's perceived abilities to make conscious decisions. Thus, some people do think you need a soul to have free will-but it is because they think you need a soul to make conscious decisions.

Free Will, Moral Responsibility, and Scientific Epiphenomenalism.

This article addresses two influential lines of argument for what might be termed "scientific epiphenomenalism" about conscious intentions - the thesis that neither conscious intentions nor their physical correlates are among the causes of bodily motions - and links this thesis to skepticism about free will and moral responsibility. One line of argument is based on Benjamin Libet's neuroscientific work on free will. The other is based on a mixed bag of findings presented by social psychologist Daniel Wegner. It is argued that both lines of argument are unsuccessful.

Approaching self-deception: how Robert Audi and I part company.

This article explores fundamental differences between Robert Audi's position on self-deception and mine. Although we both depart from a model of self-deception that is straightforwardly based on stereotypical interpersonal deception, we differ in how we do that. An important difference between us might be partly explained by a difference in how we understand the kind of deceiving that is most relevant to self-deception.

Decision/action, philosophical issues about.

Are conscious decisions or intentions ever among the causes of corresponding intentional actions? This article provides conceptual background for an examination of this question, including a discussion of the nature of decisions, intentions, and actions and a sketch of a model of conscious deciding. It also examines evidence that conscious decisions and intentions sometimes play a role in producing corresponding actions. Copyright © 2010 John Wiley & Sons, Ltd. For further resources related to this article, please visit the WIREs website.