Monkeys understand conversations

Researchers reveal a curious behavior among marmoset monkeys in Brazil, where they interpret interactions with third parties.

We all do it. At work, with our friends… Human beings surreptitiously observe the interactions between third parties to decide with whom we can collaborate in the future or from whom we should stay away. We are not the only ones. Less advanced apes act in a similar way. Anthropologists from the University of Zurich have concluded that the brazil marmosets they eavesdrop on the “conversations” of their peers and also understand them.

The researchers used thermal imaging to noninvasively measure temperature changes in the monkeys’ faces. Their goal was to quantify subtle emotional responses. «We were able to use this technique to show that marmosets did not perceive conspecific vocal interactions as the mere sum of the elements of a single call, but rather perceived them holistically, as a conversation.”says Rahel Brügger, first author of the study.

An animal experiencing increased emotional arousal will show a drop in facial surface temperature, especially in more exposed regions such as the nose. Measurement of the infrared radiation emitted by thermography makes it possible to record these changes.

For their study, the researchers used replays of vocal exchanges between marmosets, as well as calls from individual animals that did not participate in an interaction. They broadcast the playbacks from a hidden speaker and measured the monkeys’ reactions to the various simulations with thermography.

“This showed that the response to call interactions was significantly different than the response to individual calls.”Brugger says. «The marmoset monkeys can thus distinguish a dialogue between conspecifics from a pure monologue».

Preference for friendly monkeys

In the simulations, the researchers also distinguished between cooperative and competitive interactions. Once the monkeys had heard the different interactions, they were given the opportunity to get closer to the sources of the sounds. The researchers observed that the marmosets preferred to approach simulated individuals that had been engaged in a cooperative interaction with a third party.

This preference fits the social system and natural behavior of these little New World monkeys who depend on the cooperation of their group members. “This study adds to the growing evidence that many animals are not only passive observers of interactions with third parties, but also interpret them”concludes anthropology professor Judith Burkart, co-author of the study.

Font: ABC

Reference article: https://www.abc.es/ciencia/abci-monos-escuchan-escondidas-y-entienden-conversaciones-202102040119_noticia.html