I am very excited to share that my last research from my Master's degree is now out as an article in Proceedings of the Royal Society: Biology, you can read it here. We studied how chimpanzees initiate the grooming handclasp, a social custom that requires coordination from both partners.
In a grooming handclasp, two individuals clasp one of their hands, wrists, or arms overhead while grooming the other's armpit. This unique type of grooming only occurs in some chimpanzee groups, and varies in style between groups in accordance with a socially learned cultural tradition.
In contrast to human culture, where communication often plays a central role, grooming handclasps were thought to largely be initiated via one motivated individual physically shaping their partner into the desired form. However, by analyzing >130 initiations, we found that shaping is not the only way to initiate a handclasp grooming interaction.
Chimpanzees used several gestures (such as “hold” demonstrated by Debbie in the video below) to indicate their intention to GHC to a partner, who responded in turn. GHC initiations were not one-sided, set sequences, but rather flexible interactions that showed great variation. We found that chimpanzee pairs more experienced with GHCing with each other were more likely to communicate instead of shape. This suggests that how GHCs are initiated is variable and changing rather than fixed within an individual or a pair.
The main message I want to leave you with is that our study provides first evidence of communication playing a role in the coordination of a cultural practice in non-human animals, showing similarities to the rich interplay of communication and culture we find in humans.