An experiment by neuroscientists from the Higher School of Economics questioned American scientist Benjamin Libet’s hypothesis that a person realizes a decision after the brain makes it. The researchers’ work was published in the journal Neuropsychologia.
In 1983, a neuroscientist conducted an experiment in which subjects were asked to flex their wrists, remembering the moment they felt ready to perform the action. The time to realize the intention was recorded from the subjects’ own words: they watched the point of departure and when they felt the urge to bend their arms, they called the position where they found themselves. The final decision moment was determined by the precise reading of the sensor worn on the subjects’ wrist.
Electroencephalograph (EEG) measurements showed that participants in his experiments had activity in their brains 0.5–1.5 seconds before they made an intention to perform a movement, which, according to the researcher, predicted that action. Thus, according to Libet, the brain makes a decision and sends a signal to be ready before the person realizes it.
Experts from the HSE Cognitive Neuroscience Institute repeated the experiment using a hypersensitive EEG and added minor changes to one of the two participant groups. It turns out that the duration of intention awareness is affected by experimental procedures. Without training, subjects have difficulty identifying their intentions and distinguishing it from the moment of decision. According to the scientists, the instruction in the Libet task leads the participants to the feeling that the intent must appear long before the final decision is made.
Additionally, Russian neuroscientists have found no link between brain activity prior to the action and the intention to perform the action. The readiness signal was always recorded at approximately the same time, while the latter occurred at different times in the subjects. According to the researchers, this means that it reflects the overall dynamics of the decision-making process, but not the intention to do something.
Apparently, the classical Libet paradigm is not suitable for answering the question of whether a person is free to make decisions, believes the study’s author, Dmitry Bredikhin, a junior researcher at the HSE Institute for Cognitive Neuroscience.
Source: Ferra
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