Common marmoset monkeys (Callithrix jacchus) have been described as having human-like conversations according to a team of researchers from the Princeton Neuroscience Institute.
Native to Brazil, marmosets are highly social animals, using simple vocalizations in a multitude of situations: during courtship, keeping groups together and defending themselves. They also, according to the study published in Current Biology, exchange cooperative conversations with anyone and everyone – not just with their mates.
“We were surprised by how reliably the marmoset monkeys exchanged their vocalizations in a cooperative manner, particularly since in most cases they were doing so with individuals that they were not pair-bonded with,” said Asif Ghazanfar of Princeton University.
Geoffroy’s Marmoset (Callithrix geoffroyi), close relatives of the common marmoset, waiting to respond. Photo by Rhett A. Butler.
The researchers placed marmosets on opposite ends of a room separated by a visually opaque curtain to record their “phee” calls – long distance contact calls. They found that many aspects of marmoset speech patterns are very similar to those of humans. For instance, both humans and marmosets typically wait before responding to ensure that their vocalizations do not overlap. However, marmosets wait longer before responding, resulting in a three to five-second lag versus 250 milliseconds for humans. The study states that this is largely due to their longer units of conversation, which range from a three to five-second call versus a single syllable for humans.
Pygmy Marmoset (Cebuella pygmaea) in Amacayacu National Park, Colombia. Photo by Rhett A. Butler / mongabay.com
While polite communication allows for others to more easily understand what is being said, for marmosets, additionally, it can reveal important social information such as gender, identity, social group, and context. For example, a 2008 study in the International Journal of Primatology concluded that loud cries are only exhibited by infant marmosets, while alarm calls are unique to adults.
This study also provides a novel explanation for the evolution of primate communication. Since humans and marmosets are separated by millions of years, their shared fundamental vocal characteristics support the hypothesis that cooperative communication is not determined by the presence of advanced cognitive skills.
Further studies on marmoset behavior could help explain how humans learn communication skills from our parents and what causes communication disorders.
“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,” said Ghazanfar.
CITATION: Bezerra, B.M. & Souto, A. 2008. Structure and usage of the vocal repertoire of Callithrix jacchus. International Journal of Primatology, 29: 671-701.
Takahashi, D.Y., Naryanan, D.Z, & Ghazanfar, A.A. 2013 Coupled oscillator dynamics of vocal turn-taking in monkeys. Current Biology, 23: 1-7.
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