The “emotional” and “interpersonal” body in spatial cognition

Background: In order to interact effectively, we need to represent our action as produced by human beings. According to direct access theories, the first steps of visual information processing offer us an informed direct grasp of the situation, especially when social and emotional (interpersonal) components are implicated. Biological system detection may be the gateway of such smart processes and then may influence initial stages of perception fostering adaptive social behaviour. Aims: To investigate early neural correlates of human gesture detection in ecological situations with more high or low social impact, we compared scenes showing a human versus artificial agent interacting with a human agent. Method: 20 volunteers participated to the study. They were asked to observe dynamic visual stimuli showing realistic interactions. EEG was recorded and then ERP (event-related potentials) for selected ROI were computed. Each stimulus depicts an arm executing a gesture addressed to a human agent. Visual features of the arm were manipulated: in half of trials it was real; in other trials it was deprived of some details and transformed in a statue-like arm. Results: Morphological analysis revealed an early negative deflection peaking at about 155 ms. Peak amplitude data have been statistically analysed by repeated measures ANOVAs. It was found that the peak was ampler in the left anterior fronto-temporal region, in particular when the gesturing arm was human. Conclusions: The early negative deflection, N150, which we found to be different between the human and artificial conditions, is presumably associated to human agency detection in high interpersonal context