Controlling actions and experiencing control: the influence of movement execution and goal achievement on the Sense of Agency

Some recent theoretical models of the Sense of Agency - i.e., the feeling of controlling one's movements and their impact on the external environment (Aarts et al., 2012; Moore & Fletcher, 2012; Tsakiris et al., 2010) - suggest that this experience relies on the integration of various cues (Synofzik, 2008; Moore & Fletcher, 2012). However, only a few studies (Caspar, et al., 2016; David et al., 2016) manipulated in the same paradigm information about the executed movement and information about the achievement of the goal of the action. Hence, the respective roles of these two action cues for the Sense of Agency remains unclear. My Ph.D. thesis presents the results of two studies aimed at filling this gap. During my Ph.D., my colleagues and I devised a novel paradigm where participants performed a simple goal-directed action – pressing a button of a certain color – while they observed a virtual hand performing an action in a virtual scenario from a first-person perspective. The virtual action could be similar or different with respect to the one executed by the participant, and information about movement and about the achievement of the goal of the action could be independently and simultaneously manipulated. While participants performed the task, we collected direct and indirect measures of their Sense of Agency. In addition, we measured participant’s reaction times: indeed, a second aim of these two studies was to understand whether unexpected movement and goal related information also affects participant’s behavior and leads to behavioral adjustments, similarly to the commission of real errors (Danielmeier & Ullsperger, 2011). A detailed description of the paradigm, and the results of two behavioral studies where we employed it are reported in the thesis. In chapter 1, I provide an overview of literature supporting the fact that the Sense of Agency is sensitive both to the control of one's movements and to the achievement of the goal of the action. However, I also show that these two action cues were mostly investigated separately, which prevents a comparison of their relevance for the Sense of Agency. In chapter 2 I present the result of the first study. Our aim was to understand how violated predictions concerning movement execution and the achievement of the goal of the action influence the Sense of Agency. In Chapter 3, I present the results of the second study, where we compared the effects of the manipulation of information relative to movement execution and goal achievement respectively in freely chosen and cued actions. In particular, we wanted to investigate the influence of freedom to act on the Sense of Agency. Finally, in the Appendix I report preliminary results of an experiment where we investigated the neurocognitive processes (by means of Transcranial Magnetic Stimulation) underlying a different but related topic: the capacity of the individuals to exert agency, i.e., to control one’s own ocular movements when one is exposed to potentially distracting social stimuli (i.e., other’s gaze). Overall, the results of the studies described in chapters 2 and 3 suggest that the Sense of Agency is mostly influenced by movement related information, and that under some specific circumstances the feeling of control is also influenced by goal achievement and by freedom to act. Additionally, unexpected information concerning both the executed movement and the achievement of the goal of the action may lead to behavioral adjustments.