The Volitional Brain
Towards a Neuroscience of Free Will
Edited by Benjamin Libet, Anthony Freeman and Keith Sutherland
Sept. 2000, 320 pages (pbk.) ISBN 0 907845 11 8, $29.90 / £17.95
"The collection is wide-ranging in its scope . . . and reports some fascinating empirical work on the brain activity that appears to underlie volitional behaviour" A.C. Grayling, TLS
"A timely compilation of essays on the brain processes that organize voluntary action." Karl Pribram, Contemporary Psychology
Full text of Review from J. Neurol. Neurosurg Psychiatry
The readiness potential was found to precede voluntary acts by about half a second or more (Kornhuber & Deecke, 1965). Kornhuber (1984) discussed the readiness potential in terms of volition, arguing that it is not the manifestation of an attentional processes. Libet discussed it in relation to consciousness and to free will (Libet et al., 1983a,b; Libet, 1985; 1992; 1993). Libet asked the following questions: Are voluntary acts initiated by a conscious decision to act? Are the physiological facts compat- ible with the belief that free will determines our voluntary acts? What is the role of consciousness in voluntary action? In this paper I will discuss these questions and the answers that Libet gave to them.
Free will does not exist, nor can it be explained, outside the confines of subjective experience. William James, whose talent for depicting subjective experience was equal to his brother Henry's, desperately wanted to believe in free will. But his introspections did not support it.
The cornerstone of the dominant folk theory of free will is the presumption that conscious intentions are, at least sometimes, causally related to subsequent 'voluntary' actions. Like all folk theories that have become 'second nature', this model skews perception and cognition to highlight phenomena and interpretations that are consistent with itself, and pathologize or render invisible those that are not. A variety of experimental, neurological and everyday phenomena are reviewed that cumulatively cast doubt on this comforting folk model. An alternative view, more consistent with the evidence, sees intentions and actions as co-arising in complex neural systems that are capable of (fallibly) anticipating the outcomes of their own ongoing processing. Such tentative predictions, when they become conscious, are appropriated by a 'self system' that believes itself to be instigatory, and reframed as 'commands'. This confusion between prediction and control is hypothesized to arise particularly in selves that are identified in terms of a complex proliferation of partially conflicting goal-states. Such a system routinely needs to carry out detailed and time-consuming analyses of the motivational character of situations, thus creating the conditions in which anticipatory neural states surface into consciousness. The experience of 'self control' occurs when the system successfully predicts the dominance of a 'higher', more long-term or a priori less likely goal state, over another that is seen as 'lower', short-term or more likely.
Obsessive-compulsive disorder (OCD) is a commonly occurring neuropsychiatric condition characterized by bothersome intrusive thoughts and urges that frequently lead to repetitive dysfunctional behaviours such as excessive handwashing. There are well-documented alterations in cerebral function which appear to be closely related to the manifestation of these symptoms. Controlled studies of cognitive-behavioural therapy (CBT) techniques utilizing the active refocusing of attention away from the intrusive phenomena of OCD and onto adaptive alternative activities have demonstrated both significant improvements in clinical symptoms and systematic changes in the pathological brain circuitry associated with them. Careful investigation of the relationships between the experiential and putative neurophysiological processes involved in these changes can offer useful insights into volitional aspects of cerebral function.
How is mind related to matter? This ancient question in philosophy is rapidly becoming a core problem in science, perhaps the most important of all because it probes the essential nature of man himself. The origin of the problem is a conflict between the mechanical conception of human beings that arises from the precepts of classical physical theory and the very different idea that arises from our intuition: the former reduces each of us to an automaton, while the latter allows our thoughts to guide our actions. The dominant contemporary approaches to the problem attempt to resolve this conflict by clinging to the classical concepts, and trying to explain away our misleading intuition. But a detailed argument given here shows why, in a scientific approach to this problem, it is necessary to use the more basic principles of quantum physics, which bring the observer into the dynamics, rather than to accept classical precepts that are profoundly incorrect precisely at the crucial point of the role of human consciousness in the dynamics of human brains. Adherence to the quantum principles yields a dynamical theory of the mind/brain/body system that is in close accord with our intuitive idea of what we are. In particular, the need for a self-observing quantum system to pose certain questions creates a causal opening that allows mind/brain dynamics to have three distinguishable but interlocked causal processes, one micro-local, one stochastic, and the third experiential. Passing to the classical limit in which the critical difference between zero and the finite actual value of Planck's constant is ignored not only eliminates the chemical processes that are absolutely crucial to the functioning of actual brains, it simultaneously blinds the resulting theoretical construct to the physical fine structure wherein the effect of mind on matter lies: the use of this limit in this context is totally unjustified from a physics perspective.
Physics has been invoked both to refute and to support psycho-physical interactionism, the view that mind and matter are two mutually irreducible, interacting domains. Thus it has been held against interactionism that it implies violations of the laws of physics, notably the law of energy conservation. I examine the meaning of conservation laws in physics and show that in fact no valid argument against the interactionist theory can be drawn from them. In defence of interactionism it has been argued that mind can act on matter through an apparent loophole in physical determinism, without violating physical laws. I show that this argument is equally fallacious. This leads to the conclusion that the indeterminism of quantum mechanics cannot be the physical correlate of free will; if there is a causally efficacious non-material mind, then the behaviour of matter cannot be fully governed by physical laws. I show that the best (if not the only) way of formulating departures from the 'normal', physically determined behaviour of matter is in terms of modifications of the electromagnetic interactions between particles. I also show that mental states and events are non-spatial, and that departures from the 'normal' behaviour of matter, when caused by mental events, are not amenable to mathematical description.
If mind is not a part of the physical universe but is able to influence brain events, then violations of physical laws should occur at points of such mental influence. Using current knowledge of how the nervous system functions, the minimal necessary magnitude of such violations is examined. A variety of influences that could produce action potentials is considered, including the direct opening of sodium channels in membranes, the triggering of release of neurotransmitter at synapses, the opening of postsynaptic, ligand-gated channels, and the control of neuromodulation. It is shown that the magnitude of the disturbance required is significantly greater than allowed for under quantum-mechanical uncertainty. It is concluded that violations of fundamental physical laws, such as energy conservation, would occur were a non-physical mind able to influence brain and behaviour.
Hume claimed that anything that happens must either be causally determined or a matter of chance, and that a person is responsible only for choices caused by the person's character; so that if any sense is to made of free will and responsibility, it must be on the basis that they are compatible with determinism. In this paper I argue that Hume's claim depends on a covert assumption that whatever happens to any system in the world must be either the only development of the system which is consistent with causal laws, or else a development which is random. I argue that it is a serious mistake to make such an assumption covertly; and that without this assumption, good sense can be made of a concept of free will and responsibility as being indeterministic, thereby providing a viable alternative to compatibilist views
A self or person does not appear to be identifiable with his or her organic body, nor with any part of it, such as the brain; and yet selves seem to be agents, capable of bringing about physical events (such as bodily movements) as causal consequences of certain of their conscious mental states. How is this possible in a universe in which, it appears, every physical event has a sufficient cause which is wholly physical? The answer is that this is possible if a certain kind of naturalistic dualism is true, according to which the conscious mental states of selves, although not identifiable with physical states of their brains, are emergent effects of prior physical causes. Moreover, mental causation on this model promises to explain certain aspects of physical behaviour which may appear arbitrary and coincidental from a purely physical point of view.
The folk psychology view of the faculty of freewill is that it is innate, unitary, structureless and, of course, free. A bifold approach to the mind, as taken by Vygotsky, Mead, Luria and others, argues that, like all the other higher mental abilities of humans, freewill is in fact largely a socially-constructed and language-enabled habit of thought. There is a neurology for this habit to latch on to -- after all, the 'raw' animal brain is built for acting rather than contemplating. But it is the social superstructure -- the habit of monitoring and even directing our planning behaviour - which creates much of the traditional mystery. Indeed, ironically, it is actually central to the socially-constructed Western 'script' of freewill that we deny the social origins of this ability to take charge of our own brains.
I have taken an experimental approach to this question. Freely voluntary acts are preceded by a specific electrical change in the brain (the 'readiness potential', RP) that begins 550 ms before the act. Human subjects became aware of intention to act 350-400 ms after RP starts, but 200 ms. before the motor act. The volitional process is therefore initiated unconsciously. But the conscious function could still control the outcome; it can veto the act. Free will is therefore not excluded. These findings put constraints on views of how free will may operate; it would not initiate a voluntary act but it could control performance of the act. The findings also affect views of guilt and responsibility. But the deeper question still remains: Are freely voluntary acts subject to macro-deterministic laws or can they appear without such constraints, non-determined by natural laws and 'truly free'? I shall present an experimentalist view about these fundamental philosophical opposites.
This review summarizes recent experiments on neuronal mechanisms underlying goal-directed behaviour. We investigated two basic processes, the internally triggered initiation of movement and the processing of reward information. Single neurons in the striatum (caudate nucleus, putamen and ventral striatum) were activated a few seconds before self-initiated movements in the absence of external triggering stimuli. Similar activations were observed in the closely connected cortical supplementary motor area, suggesting that these activations might evolve through build up in fronto-basal ganglia loops. They may relate to intentional states directed at movements and their outcomes. As a second result, neurons in the striatum were activated in relation to the expectation and detection of rewards. Since rewards constitute important goals of behaviour, these activitations might reflect the evaluation of outcome before the behavioural reaction is executed. Thus neurons in the basal ganglia are involved in individual components of goal-directed behaviour.
Frith, C.D., Wellcome Department of Cognitive Neurology, University College London
In this paper we examine the functional anatomy of volition, as revealed by modern brain imaging techniques, in conjunction with neuropsychological data derived from human and non-human primates using other methodologies. A number of brain regions contribute to the performance of consciously chosen, or 'willed', actions. Of particular importance is dorsolateral prefrontal cortex (DLPFC), together with those brain regions with which it is connected, via cortico-subcortical and cortico-cortical circuits. That aspect of free will which is concerned with the voluntary selection of one action rather than another critically depends upon the normal functioning of DLPFC and associated brain regions. Disease, or dysfunction, of these circuits may be associated with a variety of disorders of volition: Parkinson's disease, 'utilization' behaviour, 'alien' and 'phantom' limbs, and delusions of 'alien control' (the passivity phenomena of schizophrenia). Brain imaging has allowed us to gain some access to the pathophysiology of these conditions in living patients. At a philosophical level, the distinction between 'intentions to act', and 'intentions in action' may prove particularly helpful when addressing these complex disturbances of human cognition and conscious experience. The exercise and experience of free will depends upon neural mechanisms located in prefrontal cortex and associated brain systems.
During the last decades, the enigmatic field of volition has been the
object of quantitative brain mapping studies. In this essay, emphasis will
be given to brain mapping observations during overt or imagined willed
acts in conscious normal individuals. The findings suggest that such acts
are 'formulated' in the frontal/prefrontal cortex as neuronal programs
for future motor, behavioural, verbal, or cognitive acts. During imagined
movements or speech, brain mapping reveals important prefrontal activations
which contrast to perirolandic activations during overt willed acts. In
psychiatric disorders with symptoms of a 'sick will', like in schizophrenia,
affective disorders, and organic dementia, reductions of the resting prefrontal
activity have been recorded. The relationship between will and prefrontal
activity is compatible with the view that frontal/prefrontal (efferent)
parts of the cortex are involved in the serial temporal programming of
motor behaviour, speech, and cognition. In addition, there are unconscious
mechanisms participating in volition. Electrophysiological evidence presented
by Libet (1985 et seq.) supports this view.
Do we really choose to get out of bed in the morning or is our sense of free will merely an illusion? In an age of functional imaging can philosophy still offer any solutions to the problem of volition? Is free will compatible with the laws of quantum physics?
The subject of free will, once the province of philosophy and theology, is now fair game for neuroscience, psychology, and physics. This diverse collection of articles covers all of these disciplines, old and new, providing a ringside seat for the current arguments about the nature of free will -- and even whether it exists. You are left to use your own free will (or lack of it) to judge the final outcome.
There are some complex arguments on offer but there is much to enjoy for an interested amateur -- the variety of opinions reflecting an understandable lack of consensus. I particularly enjoyed the chapter by Spence and Frith on what is known of the functional anatomy of volition and the lessons from social anthropology in McCrone's essay. Libet, who in 1983 famously described the enormous 350 ms delay between the brain's preparation to act and its conscious awareness of intention to move, explains why his experiments do not necessarily deny the possibility of free will. Other contributions include critiques of Libet's work, discussion of free will in the light of obsessive-compulsive disorder and the relation of quantum physics to volition. Even if the writing is a little dense at times, you are generally rewarded for your efforts.
Lastly, there is a highly personal contribution from Anthony Freeman, an ex-vicar, who -- despite his surname -- claims he has never taken a 'positive free-choice decision' in his life. This is an affordable book that performs well as a starting point for exploring modern answers to the ancient and thorny problem of free will.