Academic journal article South African Journal of Philosophy

Mental States, Processes, and Conscious Intent in Libet's Experiments1

Academic journal article South African Journal of Philosophy

Mental States, Processes, and Conscious Intent in Libet's Experiments1

Article excerpt


The meaning and significance of Benjamin Libet's studies on the timing of conscious will have been widely discussed, especially by those wishing to draw sceptical conclusions about conscious agency and free will. However, certain important correctives for thinking about mental states and processes undermine the apparent simplicity and logic of Libet's data. The appropriateness, relevance and ecological validity of Libet's methods are further undermined by considerations of how we ought to characterise intentional actions, conscious intention, and what it means to act with conscious intent. Recent extensions of Libet's paradigm using fMRI and decision-based tasks suffer from similar limitations. The result is that these sorts of laboratory studies of isolated, trivial, decontextualized bodily movements, in a context of extended (conscious) intentional experimental participation and cooperation, are of dubious and potentially misleading relevance to the study of agency.


Constant advances in our ability to observe and track neural activity in the working brain raise questions about how this activity is related to the reported conscious experiences and activities of the agent. Variations on these questions have been investigated since at least the 1960s2, exploiting the investigative promises and pitfalls of neuroscience' s best tools, including EEG, TMS and fMRI3. Data generated in this research tradition have and continue to be widely discussed amongst neuroscientists, psychologists, philosophers, and a range of other contributors to the interdisciplinary studies of consciousness and agency. In particular, these studies have been interpreted by some as challenging the reality of free will, with the data supposedly demonstrating that the neural drivers of behaviour are already busy before there is conscious awareness of intention, thus suggesting that conscious awareness is epiphenomenal. In this paper, I will argue that the key evidence produced in this research tradition cannot sustain the sceptical conclusions some have sought to draw from it.

The attraction and notoriety of these studies should come as no surprise. For a start, this research appears to take questions about (at least certain kinds of) mind-brain relations out of the abstract realm of philosophical theorising and into the gritty world of empirical science. Moreover, the studies at the heart of this tradition - the work of Benjamin Libet on the timing of conscious will - offered up a tantalising result. Using EEG, Libet timed the occurrence of a motor-related readiness potential, and compared this to the self-reported timing of a first awareness of conscious intention in subjects performing voluntary wrist movements4. The results suggested that conscious intention followed the onset of the readiness potential by 350 to 400 milliseconds. Here, it seemed, was a prima facie empirical puzzle worthy of serious theoretical and philosophical attention: was this potentially troubling evidence of consciousness trailing behind the 'real' neural machinery of human behaviour? Had Libet really found evidence for the origins of action lying in unconscious neural activity, rather than in conscious episodes of origination through intention formation? Did the data pose a threat to ordinary notions of free will?

Sceptical interpretations of Libet' s data - including readings of the data that are not friendly to a robust conception of conscious agency - can be found throughout the interdisciplinary literature. The neuroscientist Patrick Haggard has replicated and extended Libet's studies, and thinks the cumulative data 'challenge the classical idea of free will'5. The psychologist Daniel Wegner uses Libet's data as an important pillar of evidence in arguing that the experience of conscious will is always illusory6. Daniel Dennett thinks that Libet's evidence does little to undermine his compatibilist conception of agency7, but he does so in the context of a view on consciousness and conscious agency that many would regard as sceptical to the point of eliminativism8. …

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