Moderate manipulation to somatosensory feedback does not affect Libet-style intentional action

Area of Science:

• Neuroscience
• Cognitive Science
• Philosophy of Mind

Background:

• Benjamin Libet's experiment questioned free will, suggesting unconscious brain activity (readiness potential/RP) precedes conscious decisions.
• Alternative theories propose RP reflects accumulating signals reaching an intention threshold, but the source of these signals for arbitrary decisions is unclear.
• Interoceptive signals (e.g., cardiac, respiratory) are implicated in guiding arbitrary decisions.

Purpose of the Study:

• To investigate whether somatosensory feedback from the afferent system contributes to the signals accumulated during arbitrary decision-making.
• To test if disrupting somatosensory feedback by inducing hand numbness affects the time to reach a decision threshold.

Main Methods:

• Participants performed arbitrary decisions after their hands were made numb to block somatosensory feedback.
• Bayesian analyses were used to compare evidence for the experimental hypothesis against the null hypothesis.

Main Results:

• Bayesian analyses provided decisive evidence supporting the null hypothesis.
• There was no significant difference in decision-making time when somatosensory feedback was blocked.

Conclusions:

• Somatosensory feedback does not appear to be a substantial source of information for arbitrary decisions.
• The findings necessitate alternative explanations for the signals underlying arbitrary decision-making and the readiness potential.