ArticleAmerican journal of biological anthropology2025
Functional and Morphological Differences in the Play Face and Full Play Face in Lowland Gorillas, a Hominid Species: Implications for the Evolutionary Roots of Smile and Laugh Face.
Article in American journal of biological anthropology, 2025. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 2 papers.
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Who cites it
2 citing papers in PubMed.
- Towards the complexity of laugh communication in great apes: exact facial replications in laugh faces of orangutans and chimpanzees.Scientific reports · 2026Article
- Nuancing 'Emotional' Social Play: Does Play Behaviour Always Underlie a Positive Emotional State?Animals : an open access journal from MDPI · 2024Review
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5 authors.
Funding
Abstract
objectivePlay Face (PF) and Full Play Face (FPF) in the great apes-homologous to human smile and laugh-face-have been considered a single phenomenon. However, if natural selection has preserved two expressions, probably their adaptive value differs. MATERIALS AND
methodsWe collected video data on play interactions in two lowland gorilla groups (N = 21; Gorilla gorilla gorilla) housed at La Vallée des Singes and the ZooParc de Beauval (France). Lacking a tool tailored for gorillas during this study, we analyzed facial action-unit activation via chimpFACS and OpenFace.
resultsWe found that PF and FPF activated partly different action units as it occurs for chimpanzees and humans' PF/FPF. We detected the rapid replication (Rapid Facial Mimicry [RFM]) of either PF or FPF that was associated with longer play sessions. Not-mimicked PF was linked to increased play session variability (different types of play patterns) measured via the Shannon Index, whereas not-mimicked FPF was associated with increased play asymmetry (imbalance between offensive/defensive patterns) measured via the Play Asymmetry Index. DISCUSSION: Lowland gorillas may use PF to manage sessions that are more complex in terms of pattern types and FPF-a more salient signal-to prevent misunderstandings when the session is imbalanced. RFM of both expressions may favor the prolongation of play sessions by increasing player synchronization and possibly emotional sharing. Our study opens the door to further comparative studies on playful expressions in humans and other primates as a way to fine-tune possible emotional communication and delineate potential evolutionary roots of Hominidae facial communication.
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