Researchers reveal a scandalous trait that primates share with humans. That is their ability to eavesdrop in conversations with other monkeys.
Past experiments revealed that monkeys could forge social bonds to understand video games like how humans behave. But this new research suggests that humans and primates are perhaps more alike than previously thought.
The study, published in the journal Science Advances, reveals that marmosets can eavesdrop and evaluate monkey conversations and shows an affinity towards cooperative monkeys over the non-cooperative ones.
Lead author and Anthropology researcher from the University of Zurich, Rahel Brügger explains that the study adds to the mounting evidence that humans also pay attention to the actions of others, Inverse reported.
"The study adds to the growing evidence that common marmosets and many animals are not only passive observers of third-party interactions; they are able to understand and evaluate these interactions," she said.
Experimentation Process
Brügger and her team employed a combination of thermography and behavioral reports to understand how primates interpreted the monkey conversations. Thermography, also known as heat mapping, can help researchers to understand the feelings of animal subjects that are otherwise unseen in behavioral reports.
According to Inverse, the researchers played audio recordings of six different monkey conversations of both cooperative and non-cooperative that provoked an emotional response from the monkeys during phase A of their experiment. The audio is made by monkeys unrelated to the study which included infants crying for food to adults chattering.
The researchers observed the monkeys under an infrared heat camera while also not interrupting the socialization between the monkeys to reduce the possibility of bias or interference from human third parties.
Meanwhile, in phase B, they opened the doors to a test area where they broadcast the audio recordings to the monkeys. They created a |Hollywood-like set where there are mirrors and set design to make it appear as if there are other marmoset monkeys in the test area.
They observed how the monkeys reacted and allowed them to venture to the area and observed if they will go back to their home enclosure or not.
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How Did the Monkeys React?
According to the researchers, they found some interesting insights on how the monkeys responded to the audio calls. CNN reported that there were some sex-specific differences between them like, female helper monkeys had the strongest temperature drops in response to the audio calls which is a sign of their desire to mate.
On the other hand, male helper monkeys showed a strong increase in nasal temperature that means it was experiencing a decrease in arousal, thus indicating relaxation.
Moreover, the researchers also noted that the breeder monkeys on average did not show any signs of temperature drops but they also observed some differences. For instance, female breeder monkeys are very food motivated while the males showed greater arousal when hearing negative interactions between a young and adult monkey.
That implies male breeder monkeys serve as the caregiving members in their family. When they hear the negative audio calls, it triggered their more protective and fatherly "fight or flight" response.
Psychology Today reported that primates engage in social grooming to maintain and solidify friendships between them. Overall, the study found that marmosets have keen skills of social perception like humans. They use these skills to identify positive characteristics about their future mates and in social cooperation, which is crucial to their survival.
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