Biology subjects

Haggard, P.

Publications and source records attributed to Haggard, P..

3 recordsLinked to original sources

bioRxiv2018

Evidence for metacognitive bias in perception of voluntary action

Studies of metacognition often measure confidence in perceptual decisions. Much less is known about metacognition of action, and specifically about how people estimate the success of their own actions. In the present study, we compare metacognitive abilities between voluntary actions, passive movements matched to those actions, and purely visual signals. Participants reported their confidence in judging whether a brief visual probe appeared ahead or behind of their finger during simple flexion/extension movement. The finger could be moved voluntarily, or could be moved passively by a robot replaying their own previous movements. In a third condition, participants did not move, but a visual cursor replayed their previous voluntary movements. Metacognitive sensitivity was comparable when judging active movements, during passive finger displacement and visual cursor reply. However, a progressive metacognitive bias towards overconfidence was found for passive and for voluntary movements. Taken together, our results may partly explain some of the peculiarities that arise when one judges ones own actions.

neuroscience↗

bioRxiv2018

Dissociating cognitive and motoric precursors of human self-initiated action

Across-trial variability of EEG decreases more markedly prior to self-initiated than prior to externally-triggered actions, providing a novel neural precursor for volitional action. However, it remains unclear whether this neural convergence is an early, deliberative stage, or a late, execution-related stage in the chain of cognitive processes that transform intentions to actions. We report two experiments addressing these questions. Self-initiated actions were operationalized as endogenous skip responses while waiting for target stimuli in a perceptual decision task. These self-initiated skips were compared to blocks where participants were instructed to skip. EEG variability decreased more markedly prior to self-initiated compared to externally-triggered skip actions, replicating previous findings.\n\nImportantly, this EEG convergence was stronger at fronto-midline electrodes than at either the electrode contralateral or ipsilateral to the hand assigned to the skip action in each block (Experiment 1). Further, convergence was stronger when availability of skip responses was rationed, encouraging deliberate planning before skipping (Experiment 2). This suggests that the initiation of voluntary actions involves a bilaterally-distributed, effector-independent process related to deliberation. A consistent process of volition is detectable during early, deliberative planning, and not only during late, execution-related time windows.

neuroscience↗

bioRxiv2017

Human Self-Initiated Action Is Preceded By A Reliable Process Of Noise Reduction

A gradual buildup of electrical potential over motor areas precedes self-initiated movements. Recently, such \"readiness potentials\" (RPs) were attributed to stochastic fluctuations in neural activity. We developed a new experimental paradigm that operationalised self-initiated actions as endogenous skip responses while waiting for target stimuli in a perceptual decision task. We compared these to a block of trials where participants could not choose when to skip, but were instead instructed to skip. Frequency and timing of motor action were therefore balanced across blocks, so that conditions differed only in how the timing of skip decisions was generated. We reasoned that across-trial variability of EEG could carry as much information about the source of skip decisions as the mean RP. EEG variability decreased more markedly prior to self-initiated compared to externally-triggered skip actions. This convergence suggests a consistent preparatory process prior to self-initiated action. A leaky stochastic accumulator model could reproduce this convergence given the additional assumption of a systematic decrease in input noise prior to self-initiated actions. Our results may provide a novel neurophysiological perspective on the topical debate regarding whether self-initiated actions arise from a deterministic neurocognitive process, or from neural stochasticity. We suggest that the key precursor of self-initiated action may manifest as a reduction in neural noise.

neuroscience↗