Primate ACC encodes natural vocal interactions in a ‘cocktail party’

The Cocktail Party Problem (CPP)—extracting meaningful signals amid competing voices—remains poorly understood at the neural level, particularly in real-world contexts where it emerges naturally. We investigated the role of the anterior cingulate cortex (ACC), a structure implicated in social monitoring but rarely examined in relation to audition, to resolve the CPP in freely-moving marmoset monkeys engaged in ecological vocal exchanges. Analyses revealed that ACC is seemingly integral to resolving the CPP. Not only did neurons encode the calls of either the conversational partner or background callers, but this selectivity persisted even with overlapping background sounds, a hallmark of the CPP. Moreover, ACC activity reflected the conversational dynamics by encoding turn-taking structure, highlighting the importance of CPP resolution for navigating social interactions in complex natural soundscapes.