Elsevier

Neuroscience & Biobehavioral Reviews

Volume 47, November 2014, Pages 636-645
Neuroscience & Biobehavioral Reviews

Review
Demystifying “free will”: The role of contextual information and evidence accumulation for predictive brain activity

https://doi.org/10.1016/j.neubiorev.2014.10.017Get rights and content

Highlights

  • Free decisions can be predicted from brain activity seconds prior to awareness.

  • Sequential-sampling models can explain early predictive brain activity in free choice.

  • Free choices might be informed by subtle contextual information, e.g. choice history.

  • Demonstrated unconscious processing cannot inform the philosophical free-will debate.

Abstract

Novel multivariate pattern classification analyses have enabled the prediction of decision outcomes from brain activity prior to decision-makers’ reported awareness. These findings are often discussed in relation to the philosophical concept of “free will”. We argue that these studies demonstrate the role of unconscious processes in simple free choices, but they do not inform the philosophical debate. Moreover, these findings are difficult to relate to cognitive decision-making models, due to misleading assumptions about random choices. We review evidence suggesting that sequential-sampling models, which assume accumulation of evidence towards a decision threshold, can also be applied to free decisions. If external evidence is eliminated by the task instructions, decision-makers might use alternative, subtle contextual information as evidence, such as their choice history, that is not consciously monitored and usually concealed by the experimental design. We conclude that the investigation of neural activity patterns associated with free decisions should aim to investigate how decisions are jointly a function of internal and external contexts, rather than to resolve the philosophical “free will” debate.

Section snippets

The “free will” problem and brain activity

The belief that we have free will – that we are the authors of our own fate – is fundamental to our self-concept and our identity as human beings. Our intuition tells us that we are able to ignore the constraints of nature to some extent: we can reflect on our reasons, deliberate on our options, and consciously choose to do otherwise if we wish. The question of whether this is actually true or an illusion, or which aspects of our decisions are free and which are not, is as old as philosophy

Definitions in current brain research

Before we address those three questions, it is necessary to briefly review some definitions, because one source of confusion and controversy in current research on voluntary actions arises from a lack of a clear definition of what is being investigated. Different authors focus on different aspects of free decisions (or volition in general), including intentions, the “will”, decision-making, initiation of actions, and authorship (see Roskies, 2010). In the present paper, we will discuss them

Neuroscience research on free decisions

Despite the lack of a clear definition (Roskies, 2010), many studies have sought to investigate the cognitive and neural basis of free (or voluntary) decisions. One stream of research has focused on creating experimental situations in which some kind of action has to be initiated by the participant while either the timing (e.g., Brass and Haggard, 2007, Haggard et al., 2002, Lau et al., 2004, Lau et al., 2006, Libet et al., 1983), or the action itself (usually within a limited range of possible

Evidence accumulator models for free choice

While recent models are more concerned with dividing the decision stream into sub-processes (e.g. Haggard, 2008), the question of how decision formation takes place for voluntary choices still remains unknown. However, other recent studies help to find an appropriate decision model for voluntary decisions. It has been shown that the predictive activation patterns preceding decisions become increasingly similar over time to the patterns found at the time of the conscious decision (Bode et al.,

Brain imaging and the philosophical free will problem

We argue that the fMRI findings reviewed here do not speak to the philosophical debate about the nature of free will. There are several reasons for this conclusion. Following Batthyany (2009), from a reductionist point of view, one might argue that these studies do not speak to the free will problem more than any other study of brain activity. If we ignore concepts such as quantum randomness, and assume that all our actions, motivation, thoughts and intentions rely on brain processes in a

Conclusions

Here we have argued that the results of recent neuroimaging studies showing the predictability of decision outcomes prior to the reported conscious awareness of the decision-maker do not require a new model, nor are they mysterious. We reviewed studies suggesting that evidence accumulator models are applicable to free decisions—although the sources of this accumulated evidence are sometimes hidden. However, decisions are never made without context. In everyday life, decision-making draws upon a

Acknowledgements

The authors thank John Armstrong, Olivia Carter, Damien Crone, Daniel Bennett, Daniel Rosenblatt, Bowen Fung, Hayley McFadyen, Maia Tarrell, Christina Van Heer, Katharina Voigt, Kathleen Charles-Walsh and Carmen Morawetz for support and comments on earlier versions of the manuscript. The authors declare no conflict of interests. This work was supported by an Australian Research Council Discovery Early Career Researcher Award (DE 140100350) to S.B., a Department of Finance Initiative Project

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