If you know how to take your turn in polite conversation, you have at least one thing in common with the common marmoset. A group of researchers recorded pairs of these rat-sized monkeys (Callithrix jacchus, above) as they exchanged their piercing “phee” calls from opposite sides of a curtain. Surprisingly, the two calls never overlapped, even in exchanges lasting as long as 30 minutes. Frogs and insects are known to space out their calls so that potential mates can hear their individual voices. But the marmoset’s painfully shrill repartee is more complex and likely serves a different purpose, the group reports online today in Current Biology. This attentive creature leaves a uniform pause (about 5 seconds) before responding to its neighbor’s call, and adjusts its rhythm if the neighbor speeds up or slows down. The cooperative pattern strongly resembles human conversation, the authors say, and it doesn’t occur in our closer primate relatives, such as chimpanzees. The researchers suggest that man and marmoset both evolved turn-taking because we share important social traits: We’re highly vocal and we form social groups to care for our offspring collectively. So why does it pay to wait your turn? Alternating calls might make it easier to transmit a message over background noise. (For tree-dwelling marmosets, this message likely includes the age, sex, or location of the distant caller.) Turn-taking may also relieve stress by allowing marmosets to acknowledge one another from a distance rather than spouting random “phees” in a neighbor’s general direction. It’s comforting to know someone is listening.