Ting Zhang¹, Rui Wang^1,2, Yi Jiang^1,2; ¹Institute of Psychology, Chinese Academy of Sciences, ²Department of Psychology, University of Chinese Academy of Sciences, Beijing, China

Understanding social interactions is crucial for navigating human behavior in daily life, requiring the ability to recognize, interpret, and predict the actions of others. However, the brain mechanisms underlying the perception of social contingency in communicative interactions remain unclear. Here we combined behavioral and fMRI measurements to investigate the neural representation of social interaction by anticipating contingent actions. Participants viewed the point-light displays of two successively presented agents and performed a discrimination task (interactive or independent actions). This paradigm allowed us to test how the biological motion perception is shaped by the context of social interaction by quantifying neural activations in response to identical actions of the second agent under different social contexts, ruling out potential confounding factors such as low-level features or attentional orienting. Our results showed that people can identify communicative interactions from discrete body movements based on social contingency. fMRI analysis revealed decreased neural responses to interactive (compared to independent) motions in the right posterior superior temporal sulcus (pSTS), and the mentalizing network including the right temporoparietal junction (TPJ), bilateral precuneus and right superior frontal gyrus. However, such effects were absent in the low-level motion-selective middle temporal cortex (MT+) and body-sensitive extrastriate body area (EBA). Notably, correlation analysis showed that such social-context modulation of neural response in the pSTS was significantly associated with individual sensitivity to discriminating social interactions. Furthermore, psychophysiological interaction analysis showed increased functional connectivity of the right pSTS with the right medial prefrontal cortex, bilateral frontal gyrus, TPJ, and precuneus for the independent compared to interactive context. Taken together, our findings highlight that the pSTS serves as a hub for predicting social interaction, presumably involved in the integration of action perception and mentalization.

Acknowledgements: Acknowledgements: This research was supported by grants from the STI2030-Major Projects (2021ZD0203800), the National Natural Science Foundation of China (32430043), the China Postdoctoral Science Foundation (No. 2023T160678).