Agency detection and intentionality attribution: a time-locked rTMS investigation of rTPJ contribution

Objective To effectively interact, we need to swiftly detect other human beings, attribute agency stances and understand others’ intentions. According to direct access theories, human social understanding grounds on automatic skills and the first steps of visual information processing may already offer us an informed direct grasp of social situations. Starting from previous ERP evidences suggesting the early contribution of temporal-parietal structures in pre-reflective processes for agency-intentionality detection, we then devised a Transcranial Magnetic Stimulation (TMS) study to investigate whether temporo-parietal areas are crucial for early processing of agency and for explicit judgement of intentionality from observed behaviour. Participants 15 volunteers were asked to observe dynamic visual stimuli and to express a judgement concerning the intentionality of observed actions. Stimuli depicted realistic gestural interactions and differed in: the nature of the agent (human vs. artificial), the kind of executed gesture (instrumental vs. relational), and perceivable opportunities for interaction (position of the inter-agent). An online time-locked focused-rTMS paradigm has been administered during the task to specifically interfere with the target electrophysiological processes (stimulation conditions: sham vs. right temporoparietal junction – rTPJ vs. left temporoparietal junction - lTPJ). Results The analyses of behavioural responses revealed that participants’ response times were not modulated by experimental conditions. On the contrary, participants’ judgments of intentionality proved to be modulated both by our experimental variables and by transcranial magnetic stimulation. In particular, time-locked stimulation of rTPJ specifically decreased the attribution of intentionality to actions executed by human-like artificial agents. Conclusion Taking into account the role of rTPJ in social information processing, we suggest that its stimulation hampered higher-order information processing for pre-reflective attribution of intentionality, and that artificial human-like stimuli especially suffered the consequences of that hampering due to their perceptual ambiguity.