A pair of black-tufted marmosets. Image Credit: Miguelrangeljr via Wikimedia Commons  // CC BY-SA 3.0
Human children arenât the only primates that are eager to interrupt their parentsâ conversations. Baby marmosets do it, too.
Learning to take turns in conversation is an important aspect in the evolution of communication, scientists from the University of California, San Diego argue in a new study . You canât understand what someone else is saying if you canât hear them, after all.Â
Similar to polite humans, the common marmoset âa pocket-sized monkey species native to Brazilâdoesnât make noise when one of its brethren is talking. But just like in people, this behavior isnât automatic: it has to be learned in childhood.Â
Researchers from UCSDâs Cortical Systems and Behavior Laboratory studied the vocalization patterns of 10 young marmosets (five pairs of twins) and two sets of parents over the first year of the infantsâ lives, recording the âconversationsâ the juvenile marmosets had with their parents when they couldnât see each other. In the wild, marmosets keep in contact through high-pitched âpheeâ calls when they are separated .Â
The elder marmosets guided the behavior of their young by responding when they made the right vocalization, and ignoring them when they did something uncouth. When the young marmosets interrupted their parentsâ calls, their parents would simply not respond for several seconds, teaching them that that behavior was inappropriate in that context. If the marmosets did not interrupt, they were more likely to receive a response to their call.
A common marmoset. Image Credit:  Leszek Leszczynski via Wikimedia Commons // CC BY 2.0 Â
âWhen a parent produces a vocal response to their child, it provides a potential positive reinforcement, affirming an interest in continuing the vocal exchange,â the researchers write. âThe absence or delay of a response would, therefore, communicate that the behavior of the offspring was not appropriate.â
Furthermore, if the young marmosets produced the wrong sound (not a âpheeâ vocalization) for the context, their parents were more likely to interrupt them, seemingly a corrective measure.
Interestingly, young marmosets were significantly more likely to interrupt their father than their mother, though thereâs not a clear explanation for why. Furthermore, the young marmosetsâ âconversationsâ with their siblings didnât change as much over time as their vocalizations with their parents did, suggesting that the primates tailor their voices to the social context.
The researchers were unable to distinguish whether the marmoset parents were aware that they were actively teaching their offspring proper behavior, or if they were exhibiting normal behavior that happened to direct social learning.
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