Identifying traces of consciousness in the process of intending to act
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In 2008, Matsuhashi & Hallett created a novel version of the experimental design of Libet et al. (1983) which made it possible to get real-time estimations of a participant’s awareness of consciously willing to act. Using this method, the onset of the intention to act was measured up to 1.42s prior to movement onset, whereas Libet et al. found it only about 0.2s prior to movement. If one takes intentions to be discrete mental states these results seem to be at odds with each other, yet they fit very well within a framework in which intentions are regarded as processes developing over time. While the later stages in this process of intending are available for self-initiated report (similar to the reported intention timings by Libet et al.), early stages appear to be reachable and reportable through external probing only (as used by Matsuhashi & Hallett). However, to the best of my knowledge, no one has conducted a within-subject comparison between the Libet- and Matsuhashi-task in order to investigate whether the measured onsets of intending indeed differ significantly between the two. In this thesis, I will propose a novel conceptual framework describing intending as a process consisting of multiple stages developing over time. With this framework in mind, I conducted a new experiment, incorporating adapted versions of both the Matsuhashi & Hallett experiment as well as that of Libet et al. into a within-subject design. The results indicate that the onsets of intending as measured using external probing indeed occur significantly earlier in time (and quite close to the onset of the neural preparation for action) compared to the onsets of intending as measured using self-initiated reports, thus providing credence to the interpretation of intending to act as a process developing over time.
Faculteit der Sociale Wetenschappen