The naive brain detects face-to-face biological motion.

Detecting agents and their interactions is a cornerstone of social cognition. Vertebrates are known to possess innate sensitivity to animacy cues, such as self-propelled or biological motion, supported by subpallial circuits within the social behavior network (SBN). However, the neural mechanisms distinguishing the detection of animate motion from the recognition of socially meaningful relations remain unclear. Using visually naive female domestic chicks, we investigated the brain regions activated when observing point-light displays of hens moving face-to-face or back-to-back, a behavioral paradigm previously shown to reveal spontaneous sensitivity to social interaction. We found selective immediate early-gene expression in the nidopallium caudolaterale, homologous to the mammalian prefrontal cortex, but not in the nucleus taeniae of the amygdala and septum, subpallial areas in the SBN. This pattern suggests that while basic sensitivity to animate motion may rely on evolutionarily ancient subpallial circuits, the detection of socially relevant relations engages higher order pallial processing.