Researchers propose new way to read animals’ facial expressions
The findings revealed that crested macaques had more complex facial expressions.
Researchers from several universities have collaborated to propose a new system to define and study animal facial expressions.
The project sought to develop upon the Facial Action Coding System (FACS), to create a new method to better analyse the expressions of animals.
The FACS was devised in the 1970s, as a way to separate facial expressions into individual muscle movements called Action Units (AU). The behavioural experts have now combined this method with Social Network Analysis, which is used to examine the relationships between muscle movements.
The statistical package, known as NetFACS, will allow researchers to answer questions on how specific facial movements, combinations of movements and the facial communication system as a whole is used in humans and animals.
It is hoped that the new system will support researchers in developing their understanding of the complexity of facial communication, by analysing facial movements as well as labelling them.
The project, funded by the Leverhulme Trust, sees the universities of Portsmouth, Lincoln, Nottingham Trent, St Andrews and the French National Centre for Scientific Research unite to improve understanding of animal behaviour.
To assess its efficacy, the research team tested the NetFACS system by examining three species of macaques which varied in social tolerance– rhesus, Barbary and crested. The system would test the theory that animals living in larger groups, with more complex relationships and social roles, would demonstrate more complex communication.
Using the FACS for macaques, known as MaqFACS, the experts coded the facial behaviours of macaques in more than 3,000 interactions across aggressive, submissive and affiliative contexts.
The findings revealed that crested macaques, the more tolerant species, had more complex facial expressions and used a higher diversity of facial behaviour more often.
Dr Alan Rincon, the study’s lead author from the University of Portsmouth, said: “We were able to predict whether an animal was being aggressive, submissive or affiliative from their facial behaviour MaqFACS better than chance in all three species.
“However, prediction accuracy was lowest for the more tolerant and socially complex species, the crested macaques, indicating that they have a more complex facial communication system.
“Overall these results support the predicted link between social and communicative complexity and therefore help us better understand the evolution of communication.”
The researchers will continue to develop their understanding by looking at how factors such as social status and integration are linked to facial communication.
The full study can be found in the journal eLife.
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