Funded Grants

Progress in understanding voluntary action

The ability to act voluntarily is fundamentally important to our lives, yet is often taken for granted until we are robbed of that ability by disease or circumstances. For centuries, volition has been subject to religious and philosophical enquiry. Nowadays, most would agree that volition is closely connected with the brain. However, a neuroscientific understanding of voluntary action must include a mechanism for behavioural choices, and include the sense that we cause our actions (called agency), drawing on psychology and computational biology. Clinical disorders of volition studied alongside healthy cognition can greatly illuminate the mechanisms involved. This program will consider one disease in particular, the Pick’s Disease Complex (PDC), as it causes several distinct problems with voluntary action.

There are three key challenges to this research. The first is that volition is not absolute, as described in the traditional dichotomy between free will and determinism, but variable. Actions may be impossible (e.g. I cannot fly), weighted by differences in outcome (e.g.do I select the rotten or the ripe apple?) or equivalent (e.g. which of two identical buttons should I press?). There is therefore a spectrum of possible acts with variable degrees of volition, which needs to be understood and formalised.

The second challenge is to develop a neurocognitive model of volition without an implicit homunculus. Some models attribute agency to higher order neurocognitive processes (as an implied homunculus) but do not address fundamentally how voluntary decisions arise. We will instead use biologically motivated neural accumulator models to study key features of voluntary action. For example, when given a series of free choices, why can healthy people not choose at random? How are current choices so strongly influenced by previous actions? We will also address the profound lack of volition in PDC, developing a model of apathy based on dissipation of decision information by ‘leaky’ accumulators.

The third challenge we call epistemological opacity: that is, people cannot simply tell us what was happening at the moment of voluntary action. Experiment, not introspection, is required. Although one cannot measure agency directly, we will examine ‘behavioural signatures’ of agency including intentional binding (in which agency creates the perception that actions and outcomes are closely bound together in time) in PDC, and intentional priors (which distort the perceived outcomes of our own actions).

The approach makes several key problems of volition and agency tractable for scientific enquiry. The aim is to increase our understanding of this important aspect of normal human cognition. The subject is not only of interest to psychologists, but many academic disciplines, with potentially far-reaching effects ranging from optimising social and economic decisions to accelerating motor skills training. Among clinical neurosciences, a better understanding of volition and agency may alter the approach to rehabilitation after brain injury, and explain difficult behaviours in PDC and related diseases.