Everyone knows it's rude to interrupt, and so too it seems do marmosets.
Like humans, the monkeys follow the rules of polite conversation, chatting to one another in turn for up to 30 minutes at a time.
Lead researcher Asif Ghazanfar, from Princeton University in the US, said: "We were surprised by how reliably the marmoset monkeys exchanged their vocalisations in a co-operative manner, particularly since in most cases they were doing so with individuals that they were not pair-bonded with .
"This makes what we found much more similar to human conversations and very different from the co-ordinated calling of animals such as birds, frogs, or crickets, which is linked to mating or territorial defence."
Not even our closest cousins, chimpanzees, converse in the same civilised way, the scientists said.
When they vocalise at all, they tend to shout over each other.
Marmosets are unusual because of two features they share with humans: they are generally friendly with one another, and they communicate primarily by making vocal sounds.
Both qualities are likely to support the self-monitored give and take that good conversation requires, the researchers suggested.
To investigate further, they placed marmosets in opposite corners of a room in which they could hear but not see each other and recorded their exchanges.
They found that the monkeys typically waited for around five seconds after one individual had made a call before responding.
In other words, they followed their own rules of conversational etiquette.
Further marmoset studies may shed light not only on why humans communicate with each other as they do, but also why conversation can sometimes break down.
"We are currently exploring how very early life experiences in marmosets - including those in the womb and through to parent-infant vocal interactions - can illuminate what goes awry in human communication disorders," Dr Ghazanfar said.
The research was reported in the journal Current Biology.