Scientists from the University of Zurich played audio recordings of vocal interactions between their peers and recorded their behavior and body temperature to determine their response, the American Association for the Advancement of Science said in a news release.
The animals reacted differently based on their sex as well as their social status – those who had offspring known as breeders, or those who had no offspring known as helpers.
Researchers played recordings of an adult of the opposite sex who interacted with a begging baby, whether they made 21 educational marmoset food groups or aggressive calls.
The scientists also played the begging baby, and the adult’s food supply and aggressive calls are recalled individually as a check.
Marmosets and other monkeys’ noses change temperature according to their emotional state, with stress leading to a drop in temperature as blood flows to central organs, Rahel Brügger, a doctoral candidate in anthropology at the University of Zurich, told CNN .
Researchers measured the temperature change when marmosets listened to the individual calls and to the two marmosets.
According to the scientists, the change in nose temperature was greater when the marmosets listened to an interaction than the sum of the temperature change when they heard the individual calls, which led to the conclusion that marmosets interpret the interactions as conversations.
“These marmosets are not just passive observers of interactions with third parties, but really interpret and understand what third parties are doing,” Brügger said.
In general, the helper marmosets recorded greater temperature changes than their breeders.
The noses of female helper marmosets get colder after listening to men interact with babies, as this indicates a neighboring group of young monkeys and the presence of competing females. “By nature, this situation would be difficult for these marmosets,” Brügger said.
The nose temperature of male helpers has risen after listening to aggressive interactions or a female call in itself, as this may indicate a potential mating partner, Brügger explained.
“Different stimuli for different individuals can mean different things,” Judith Burkart, a researcher at the university and Brügger’s doctoral supervisor, told CNN.
The team then tested whether the marmoset would seek interaction with the monkey or the aggressive monkey by opening two doors simultaneously.
One door allows them to return to the original enclosure, while the other door leads to an additional room from which a hidden speaker plays the food part or aggressive interaction.
Marmosets had a preference for cooperating adults as they were more likely to walk through the door where the call to share food was, Brügger explains.
“They are even more curious about the potential mating partner if they assume (based on the playback) that the potential partner is a collaborative rather than a competitive partner,” she said.