Event Detail

The growing body of neurophysiological research on the question of free will, or the lack thereof, originated with the finding of Libet, et al. that the reported time of decision to make a simple action comes at least 300 ms after the beginning of the readiness potential. The readiness potential is a component of the EEG that preceds an daction by 1000 ms or more. Conscious will thus seems a latecomer in the process of choice, not the instigator. We tested whether the report of decision time marks an event in the brain, as is assumed, or is rather a post-response inference as to when the decision to act must have taken place. In Experiment 1 we use a delayed auditory beep as feedback to make the act appear to happen later than it did. The reported time of action moved forward in time proportionally to the delay in feedback, in accord with the hypothesis that the judgment of decision time is an intuitive inference of when the decision was made. In a second experiment we had participants view a delayedvideo image of their hands pressing the response button for the task. The video delay was 120 ms. The video delay shifted the judged time of decision by 40 ms. The fact that the shift in the inferred moment of decision was less than the delay suggests that tactile cues as well as visual ones contributed to the perception of when the response took place. In the third experiment the participants watched a video of button-pressing with the Libet clock in view behind the hand. The participants were to report the clock time at which they thought the person doing the pressing decided to press the button. The time estimated to be the point of conscious decision was 137 ms before the press, very close to the estimate for the participants’ report of their own decision to press the button, whether they had previously served in the experiment or were naïve to it. The hypothetical time of conscious decision, if it exists, must come before the response and therefore could not be changed by any cue that makes the response seem even later. The clear conclusion from the post-response effects on judged decision time is that the subjective time of decision is retrospectively inferred from the perceived time of response. This finding strikes us as fundamentally changing the grounds of debate about conscious will. For proponents of free will it could be cited as a welcome disconfirmation of the finding that an unconscious brain process determines the action before conscious choice. However, for the same proponents it undermines the role of conscious choice in action. For any theory of volition it shows that the conscious representation of action does not reflect critical components of the associated brain activity.