Playful interactions and facial mimicry in infant bonobos (Pan paniscus)

Abstract

The capacity to promptly and congruently respond to others’ facial signals has at its basis a mirror neuron mechanism. In Rapid (< 1 sec, RFM) and Delayed (1–5 sec, DFM) Facial Mimicry the expression emitted by an individual (trigger) is perceived and replicated by an observer. The occurrence of mimicry phenomena has been demonstrated almost exclusively in the play domain. Here, we aim at evaluating the presence of RFM/DFM during playful interactions between infant bonobos (Pan paniscus), one of the most playful primate species. We video-recorded 435 play sessions between five infants (< 48 months of age) belonging to the bonobo colony hosted at the Wilhelma Zoo (Germany). Via a frame-by-frame video-analysis, we demonstrated the presence of both RFM and DFM. These two phenomena were enhanced by face-to-face interactions between playmates. Hence, the access to others’ faces allows the player to perceive, decode and replicate signals, thus promoting a mutual intersubjective engagement with the partner. The occurrence of DFM suggests that in bonobos, as in chimpanzees, such mirror event is present just starting from infancy. The less automaticity characterizing DFM compared to RFM could be due to the involvement of more complex and time-demanding cognitive processes. Neither RFM nor DFM increased the duration of play sessions. Probably, the mimicry phenomena in infant bonobos are not recruited for manipulating the sessions, which are highly balanced and fair, but possibly for sharing the playful mood between interacting subjects thus increasing their level of familiarity and affiliation.

KEY WORDS:

• play face
• face engagement
• ontogenetic pathways
• playful mood
• symmetric play
• Pan paniscus

ACKNOWLEDGEMENTS

We wish to thank Elisa Demuru and Cristina Giacoma for inviting us to contribute to the special issue. We are grateful to the Wilhelma Zoo (Germany) and specifically the mammal curator Marianne Holtkötter and bonobo keepers for allowing and facilitating this work.

DISCLOSURE STATEMENT

The authors declare no competing interests.

ETHICAL STANDARD

The present study was purely observational, and animals were not manipulated. The University of Pisa (OPBA committee) waived the need for ethical approval according to the Italian and European guidelines and regulations. The authors had the permission of the Wilhelma Zoo (Stuttgart, Germany) to make videos on bonobos.

AUTHOR CONTRIBUTION

E. Palagi and G. Cordoni conceived and designed the experiment; M. Bertini, G. Annicchiarico and C. Bresciani collected data; E. Palagi trained M. Bertini and G. Annicchiarico for the data analysis and checked for reliability; M. Bertini and G. Annicchiarico performed the video-analysis; E. Palagi and C. Bresciani carried out the statistical analyses. E. Palagi and G. Cordoni wrote the manuscript. All authors reviewed the manuscript. E. Palagi and G. Cordoni share the senior authorship.

SUPPLEMENTAL DATA

Supplemental data for this article can be accessed at https://doi.org/10.1080/03949370.2021.1988723

DATA ACCESSIBILITY

All data (.csv) analysed in this study are provided as Supplementary Information files.

Additional information

Funding

This research did not receive any grant from funding agencies in the public, commercial, or not-for-profit sectors.