Summary: A recent study challenges the long-standing Libet paradigm about free will.
The team discovered that the EEG activity, dubbed readiness potential, registered before decision-making in Libet’s original experiment has no direct correlation to the actual decision.
Moreover, the study revealed that the moment of conscious intention can be influenced by experimental procedures. This ground-breaking research suggests that the Libet paradigm may not be the definitive answer to the complex question of human free will.
- The new research disputes the link between readiness potential and conscious decision-making previously established by Benjamin Libet.
- The study found that experimental procedures could impact the timing of conscious intention awareness.
- The researchers suggest that the Libet paradigm may not be suitable for assessing the concept of free will.
The dispute about how much free will people have in making their decisions has been going for decades. Neuroscientists have joined this discussion thanks to the electroencephalographic (EEG) experiments of Benjamin Libet.
In the 1970-1980s, he showed that 0.5–1.5 seconds before conscious awareness of the intention to perform a movement, subjects emit EEG activity that predicts this movement.
It turns out that the brain makes a decision and sends readiness potential before a person realizes it, and our actions are nothing more than the result of an unconscious physiological process in the brain.
The results of Libet’s experiments have generated a lot of controversy about free will, and some neurophysiologists have even concluded that it does not exist.
Moreover, Libet’s experiment has been repeated using functional magnetic resonance imaging, and it turns out that the decision of the subject can be predicted even 6-10 seconds before their conscious awareness of it.
The staff of the HSE Institute for Cognitive Neuroscience questioned this experimental paradigm and in their new study confirmed that the time of intention awareness in Libet’s experiments was determined incorrectly.
In addition, EEG activity, or the brain signal indicating the readiness of a decision, which was recorded by Benjamin Libet before the decision was made, actually has no direct link to this decision.
In the Libet’s original experiment, the subjects were asked to occasionally bend their wrists and at the same time remember the moment when they felt ready to perform this action.
The time of intention awareness was recorded from the words of the subjects themselves: they observed a point that moved along the screen-dial, similar to a clock hand, and indicated the position of the point when they felt the desire to bend their hand.
The moment of the final decision was determined by the exact reading of the sensor attached to the wrist of the subjects.
The HSE neuroscientists repeated the experiment with two groups of subjects, adding small changes to the task in one of the groups. Using behavioral reports and hypersensitive EEG techniques, the scientists investigated the correlation between the time of intention awareness and the time of final decision.
It turned out that the time of awareness can be influenced by experimental procedures: for example, without certain training, the subjects are barely able to determine their intentions, and the traditional Libet paradigm pushes them to the feeling that they can determine the moment of decision-making and intention.
Apparently, the instruction itself in the Libet task makes the participants feel that the intention should emerge long before the final decision is made.
In addition, the study confirmed that there is no direct link between the activity of the brain preceding the action and the intention to perform the action. The sense of intention emerged in the subjects at different points in time, whereas the readiness potential was always registered at about the same time.
Thus, the readiness potential may reflect the general dynamics of the decision-making process about making a move, but it does not mean that the intention to act has already been generated.
“Our study highlights the ambiguity of Libet’s research and proves the absence of a direct correlation between the brain signal and decision-making.
“It appears that the classical Libet paradigm is not suitable for answering the question of whether we have free will while making decisions. We need to come up with a new approach to this extremely interesting scientific puzzle,” says Dmitry Bredikhin, author of the research, Junior Research Fellow at the Centre for Cognition & Decision Making.
“Neuroscience tries to answer key questions in our life, including questions of free will and responsibility for our actions. We need to be especially precise in order to draw conclusions that affect our outlook and attitude to life. Therefore, we tried to understand the predetermination of our decisions and confirmed a number of shortcomings in the famous experiments of Benjamin Libet.
“This does not mean that we have closed this issue of the illusory nature of our free will, but rather emphasizes that the discussion continues. This might be one of the most interesting questions in modern science, to which we have yet to give a definitive answer,” comments Vasily Klucharev, Project coordinator, Leading Research Fellow of the Institute for Cognitive Neuroscience.
About this neuroscience and free will research news
Original Research: Open access.
“(Non)-experiencing the intention to move: On the comparisons between the Readiness Potential onset and Libet’s W-time” by Dmitry Bredikhin et al. Neuropsychologia
(Non)-experiencing the intention to move: On the comparisons between the Readiness Potential onset and Libet’s W-time
A seminal study by Libet et al. (1983) provided a popular approach to compare the introspective timing of movement execution (the M-time) and the intention to move (the W-time) with respect to the onset of the readiness potential (RP).
The difference between the W-time and the RP onsets contributed significantly to the current free-will discussion, insofar as it has been repeatedly shown that the RP onset unequivocally precedes the W-time.
However, the interpretations of Libet’s paradigm continuously attract criticism, questioning the use of both the W-time and the RP onset as indicators of motor intention.
In the current study, we further probe whether the W-time is rather an intention-unrelated product of the participant’s inference than an unambiguous temporal marker of the intention to move.
Using behavioral reports and concurrent multichannel EEG, we investigated the relationship between the W-time and M-time introspective reports in two groups of participants who started an experiment with a series of different reports.
Congruently with previous studies, we have shown that the W-time is affected by the experimental procedures: participants who had prior experience reporting the M-time provided significantly earlier W-time.
However, contrary to previous papers, we revealed that even naive participants do introspectively differentiate the W-time and the M-time, which suggests that the W-time might actually reflect the intention to move, at least to some extent. We, therefore, suggest that training-based modulation of the W-time values may explain this finding.
Moreover, we further confirm the absence of a direct link between the RP onset and the W-time by showing no covariation between them in both experimental groups. In turn, our findings question the overall interpretation of the comparison between these two time points.
Overall, our study further emphasizes the ambiguity of Libet’s paradigm, and suggests that the relatedness of both the RP and the W-time to the movement initiation processes should not be assumed a priori.