Extending the MaqFACS to measure facial movement in Japanese macaques (Macaca fuscata) reveals a wide repertoire potential

• DOI: 10.1371/journal.pone.0245117
• Publication Date: 2021-01-07T21:57:25Z
• Authors: Catia Correia-Caeiro; Kathryn Holmes; Takako Miyabe-Nis...
• Keywords: Facial muscles

Facial expressions are complex and subtle signals, central for communication emotion in social mammals. Traditionally, facial have been classified as a whole, disregarding small but relevant differences displays. Even with the same morphological configuration different information can be conveyed depending on species. Due to hardwired processing of faces human brain, humans quick attribute emotion, difficulty registering movement units. The well-known FACS (Facial Action Coding System) is gold standard objectively measuring expressions, adapted through anatomical investigation functional homologies cross-species systematic comparisons. Here we aimed at developing Japanese macaques, following established methodology: first, considered species’ muscular plan; second, ascertained other primate species; finally, categorised each independent into Units (AUs). similarities rhesus macaques’ musculature, MaqFACS (previously developed macaques) was used basis extend tool while highlighting appearance changes between two We documented 19 AUs, 15 Descriptors (ADs) 3 Ear (EAUs) all movements found macaques. New were also observed, indicating slightly larger repertoire than or Barbary Our work reported here extension when together MaqFACS, comprises valuable objective standardised analysis macaques will now allow evolution primates, well contribute improving welfare individuals, particularly captivity laboratory settings.