Communication, whether it is verbal or non-verbal, or based on something you see, is a huge part of the life that we lead everyday. What we take away from communication, whether it is something learned, or a signal on how to behave, also contributes to the importance of communication in everyday life. However, behaviorally coordinated communication is not just done by humans, but is carried out by chimpanzees as well!
Chimpanzees, which are some of our closest animal relatives, often communicate through gestures and physical interactions. Through an action known as a grooming handclasp (GHC), which requires coordinated behavior between two chimpanzees, this communication is able to be expressed, and contribute to the culture of chimpanzee communities. However, what sets this GHC behavior apart is that it is physically shaped, and in a way taught, rather than being based on environmental interactions. Because grooming handclasps require communication from both chimpanzees that are carrying out the GHC, researchers believe that this behavior is in a way coordinated, something that is uncommon in a vast majority of non-human animals.
In order to find whether or not these chimpanzees did coordinate their behavior, 52 wild chimpanzees had their behaviors analyzed in the wild via video recording. GHC encounters were counted using this video technique, while angle of the view of the GHC and the duration of each grooming session were taken into account. Furthermore, to investigate how the behavior was taught and earned, pairings of mothers and their offspring were studied to see whether or not familial relation had any bearing on the amount of GHC occurrences. Because of this familial relation between mother and child, it was hypothesized that chimpanzees with more GHC experience and a familial bond would engage in more grooming handclasps.
This study found that there were seven non-GHC gestures that had a higher frequency, suggesting that they were the mechanisms behind GHC behavior. These gestures were: elbow hold, hand grab, elbow touch, hand touch, head move, head touch, and hold. Additionally the researchers found that there were three outcomes for the behaviors observed: shaping, communication, and synchrony. The shaping behaviors included elbow hold and hand grab, signifying that these two behavioral types were more about the physical touch, and making sure that the learning chimpanzee could carry out the GHC behavior. Meanwhile, the elbow touch, hand touch, head move, head touch, and holding gestures fell into the category for communication, meaning that these behaviors signified that a GHC interaction was about to occur. The most complex of the outcomes was the category of synchrony, which measured how closely (in terms of time), the chimpanzees initiated the GHC. The results regarding the synchrony in the chimpanzees were recorded in their bouts of grooming and GHC behavior, as it was found that more experienced chimpanzees had higher levels of synchrony. Additionally, it was found that mother-child pairings relied more on physical shaping gestures, while non-familial pairings relied on communication, seemingly illustrating the bond and willingness for a mother to teach her offspring different behaviors.
Overall, the researchers found that in addition to intentional communication for organizational purposes, chimpanzees are also able to coordinate their behaviors with others in order to carry out the cultural GHC interaction. This coordination is also unique because of its non-verbal aspect, making the behavior completely coordinated on actions, rather than a sensory signal. This study also found that there is one more dominant chimpanzee that coordinates and shapes the GHC behavior, while another chimpanzee learns this coordinated GHC technique. Thus, because of the coordination and cultural aspect of this GHC exchange, scientists want to do more research not only on behavior, but on Chimpanzees and other primates as well, in order to see just how similar their behavior and communication is to humans.
Goldsborough Z, Schel AM, van Leeuwen EJC. 2023 Chimpanzees communicate to coordinate a cultural practice. Proc. R. Soc. B 290: 20221754. https://doi.org/10.1098/rspb.2022.1754
