The Role of Endogenous Input in defining Self-Generated Action: A Multi-Measurement Study Comparing Markers of Volition

Voluntary actions are commonly described as self-generated, yet the mechanisms that make an action self-generated remain debated. Schüür and Haggard (2011) proposed that self-generation depends on integrating multiple types of input. Here, we extend this account by testing not only the amount of input but also its nature, specifically whether the input is exogenous (specifying which action to perform) or endogenous (information that must be internally processed to select an action).In this pre-registered multi-measurement study, 39 participants performed a Random Dot Kinematic task under four conditions that varied in input quantity and endogenicity: Instructed (one option; exogenous input), Semi-Instructed (four endogenous options), Recommended ( eight endogenous options plus one exogenous recommendation), and Free (eight endogenous options). We measured three markers of volition: self-reported Sense of Volition (SoV), Temporal Binding (TB), and the Readiness Potential (RP).SoV increased progressively across the four conditions—Instructed, Semi-Instructed, Recommended, and Free—supporting the idea that both the amount and the endogenicity of input shape the subjective experience of self-generation. In contrast, TB and RP primarily differentiated the Instructed condition from the other three conditions. These results suggest that implicit and neural markers of volition are mainly sensitive to whether actions rely on exogenous versus endogenous input, rather than to graded variations in input quantity.Overall, our findings indicate that whether the environment or the agent provide the input guiding the action plays a central role in defining self-generated action. Incorporating the endogenous–exogenous distinction refines current neuroscientific accounts of volition and highlights the importance of the self-generation of the decision about which action to perform, not merely about the initiation of movement.