However, measuring intention in real-time remains challenging due to its ambiguous neural substrate.
The relationship between intentionality, movement execution, and free will is a complex and longstanding topic of philosophical and scientific inquiry. Understanding this relationship involves exploring how these concepts interact and whether human actions are truly under our conscious control or subject to deterministic or external influences.
- Intentionality: Intentionality refers to the capacity of conscious beings to have mental states and direct their thoughts and actions towards specific objects, goals, or purposes. It involves forming intentions and representing mental states about the world. Intentionality is an essential aspect of human cognition and decision-making.
- Movement Execution: Movement execution is the physical act of carrying out actions based on our intentions. When we decide to do something, our brain processes the intention and translates it into motor commands that lead to bodily movements. This process involves a complex interplay between the brain, nervous system, and muscles.
- Free Will: Free will is the philosophical concept that suggests individuals have the ability to make choices and decisions autonomously, independent of external determinants. It implies that humans have control over their actions and can consciously choose between different courses of action.
The seminal paradigm introduced by Libet et al. in 1983 allows participants to report the timings of intention formation (W-time) alongside concurrent neural activity, specifically the Readiness Potential (RP), which precedes movement onset.
The discrepancy between the W-time and RP onset has sparked debates on the causal role of conscious intention in voluntary movement initiation and its implications for the free will discourse.
Understanding the relationship between the W-time and RP onset is essential for interpreting Libet-like studies and their relevance to questions of free will. This article explores the conditions necessary for drawing meaningful conclusions from these studies and highlights the challenges in deciphering the causality between intention and RP.
Moreover, we discuss the participants’ ability to precisely estimate the time of intention formation and differentiate between the W-time and the perceived time of movement execution (M-time).
Finally, we propose a novel EEG-based experimental design inspired by previous studies, which could shed light on the interconnection between the RP onset and the W-time and provide valuable insights into the nature of intentionality.
The Complex Phenomenon of Intentionality and Free Will
Intentionality, the conscious experience of intending to perform a movement, is a crucial element of the sense of agency. It is associated with the belief that we are in control of our actions and have the capacity to make choices freely. The understanding of intentionality’s neural basis remains elusive, but its significance is well-established in studies exploring the sense of agency (Moore, 2016; Vinding et al., 2013).
Libet’s Paradigm and the Role of Readiness Potential (RP)
Libet’s paradigm offers a unique approach to investigate intentionality and its relationship with neural activity. Participants report their W-time, the moment they consciously experience intending to move, while the RP is simultaneously recorded. The RP represents a pre-movement electrophysiological activity observed in the brain before voluntary movements (Kornhuber & Deecke, 1965).
Challenging the Direct Comparison of W-time and RP Onset
The validity of directly comparing the W-time and RP onset has been questioned (Haggard & Eimer, 1999; Sanford et al., 2020; Schlegel et al., 2013). A causal chain is proposed as
“Consciously-Inaccessible Onset of Pre-Intentional Event → Consciously-Accessible Intention Onset → The Movement” to link the RP onset, W-time, and movement initiation.
However, the RP might not be equivalent to the intention onset but instead represent a pre-intentional event. Furthermore, the experimental design in previous studies might have confounded the W-time reports, leading to biased interpretations.
Differentiating W-time and M-time Reports
Studies suggest that participants might struggle to accurately differentiate between the W-time and M-time (Dominik et al., 2017; Sanford et al., 2020). Participants who first reported M-time and then W-time were more likely to distinguish the two timings accurately. This finding raises questions about the nature of W-time and the potential bias in reporting artificially earlier W-time values.
Proposed EEG-Based Experimental Design
To address the limitations and challenges in interpreting previous findings, we propose an EEG-based experimental design based on the approach suggested by Dominik et al. (2017). In this design, participants are explicitly divided into two groups: those who initially report M-time and then W-time (M-first participants) and those who report W-time first (W-first participants). This division aims to differentiate between “genuine” and “confabulated” W-time reports.
Hypotheses and Expected Outcomes
We hypothesize that W-time and M-time will significantly differ only in M-first participants, replicating previous findings. Additionally, we expect to observe a correlation between RP onsets and W-time only within the M-first participants, suggesting a genuine relationship between intention formation and RP.
Understanding the complex relationship between intentionality, movement execution, and free will requires careful consideration of experimental designs and interpretation of results. By implementing the proposed EEG-based experimental design, we aim to shed light on the nature of intentionality and its neural correlates, contributing to the ongoing discourse on free will and agency.
Clarifying the causality between intention and RP would deepen our understanding of human volition and its neurophysiological basis.
reference link: https://www.sciencedirect.com/science/article/abs/pii/S0028393223001045?via%3Dihub