2025/07/04 by Edwin J. C. van Leeuwen, Emile Bryon, Alex Rogers +3 · 1 voice
Psychology · #Action Observation and Synchronization #Child and Animal Learning Development #Cognitive psychology #Communication #Developmental psychology #Primate Behavior and Ecology #Psychology #Social psychology
paper · doi:10.1163/1568539x-bja10313
published in Behaviour 162(6-8), 459-476 (Brill)
openalex publication_date 2025/07/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Abstract Studying animal culture has been insightful for understanding the complexities of knowledge transmission and tracing human culture’s evolutionary origins. Most studies in this field have focused on material culture — behaviours that involve the use of tools and objects in ways that provide clear practical benefits to the individuals. We have previously documented a tool-use tradition without discernible function in which chimpanzees replicated the practice of inserting blades of grass in their ears from one persistent inventor. Now, over a decade later, we have observed an unrelated group of chimpanzees at the same African sanctuary, where five out of eight individuals began wearing grass in their ears and six out of eight from their rectums within a short period of time. Neither of these behaviours were observed in any of the seven other sanctuary groups ( ), except for two males in the original grass-in-ear group. Network-based diffusion analyses revealed a strong signature of social transmission for both variants. We conclude that chimpanzees adopted non-instrumental behaviours from each other and discuss how the study of social traditions without clear adaptive function could advance the field of comparative cultural evolution.