Socially tuned: brain responses differentiating human and animal motion.

Typical adult observers demonstrate enhanced behavioral sensitivity to human movement compared to animal movement. Yet, the neural underpinnings of this effect are unknown. We examined the tuning of brain mechanisms for the perception of biological motion to the social relevance of this category of motion by comparing neural response to human and non-human biological motion. In particular, we tested the hypothesis that the response of the right posterior superior temporal sulcus (pSTS) varies according to the social relevance of the motion, responding most strongly to those biological motions with the greatest social relevance (human > dog). During a functional magnetic resonance imaging (fMRI) session, typical adults viewed veridical point-light displays of human, dog, and tractor motions created from motion capture data. A conjunction analysis identified regions of significant activation during biological motion perception relative to object motion. Within each of these regions, only one brain area, the right pSTS, revealed an enhanced response to human motion relative to dog motion. This finding demonstrates that the pSTS response is sensitive to the social relevance of a biological motion stimulus.