What is it about?

Common marmosets use many facial expressions on their social interactions, just like people do. Facial expressions in humans are very important in communication and emotion expression. People can perceive emotions, intentions, and communication just by looking at another person's face. However, reading and understanding facial expressions in other species is a much harder task. Each species tends to display different facial expressions in different situations and researchers need to learn and decode each facial expression, just like if it was a foreing language. Hence, our research team at Kyoto University adapted the widely used tool used for human facial expressions called FACS - Facial Action Coding System - to common marmosets and created the new CalliFACS tool - The common marmoset Facial Action Coding System. This tool will allow researchers to study common marmosets facial expressions in an objective way.

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Why is it important?

Common marmosets are small arboreal primates that live in Brazil. These small primates have been increasingly used for laboratory experiments due to their similarities with humans and ease of being kept in captivity, slowly replacing other species such as macaques. In particular, they are often used for neuroscientific and biomedical experiments, which bring welfare concerns. Understanding how individuals react positively or negatively to their environments and conditions is of interest to mantain high welfare standards. In addition, even though these abundant primates are very social and facially expressive, their facial communication has not yet been widely studied. Hence, having a tool such as CalliFACS will allow the objective and detailed examination of how marmosets communicate with each other and how they facially react to situations.


With this new CalliFACS tool I hope researchers and other people working with common marmosets find this tool useful and apply it to further our understanding of this species rich social communication.

Dr Catia Correia-Caeiro

Read the Original

This page is a summary of: CalliFACS: The common marmoset Facial Action Coding System, PLoS ONE, May 2022, PLOS,
DOI: 10.1371/journal.pone.0266442.
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