An article on bonobo head-shaking has just appeared in the scientific journal Primates by the investigators Christel Schneider, Josep Call and Katja Liebal from the Free University in Berlin and the Max Planck Institute for Evolutionary Anthropology in Leipzig. The article is called Do bonobos say NO by shaking their head? In this report new observations are described of bonobos shaking their head horizontally from side to side, in an apparent effort to prevent another bonobo from doing something. The scientists suggest that this head-shaking by bonobos may be a primitive precursor of the head-shaking behaviour in humans, which is generally associated with a negative connotation, being a head gesture that signals “no” in many cultures.
Head gestures have been described before in chimpanzees, bonobos and gorillas, but not in orangutans. Head shakes (moving the head horizontally from side to side) had been observed before in the African great apes, but these generally occurred when the apes solicited play from their conspecifics. Only two isolated reports exist of the head-shaking possibly signaling “no” in chimpanzees, by the Dutch scientists Adriaan Kortlandt (1969) and Frans de Waal (1982). The new observations by the German scientists provide further material that suggests that bonobos shake their head in situations where they are preventing (or trying to prevent) another bonobo from engaging in a certain activity. The observations were made of bonobos living in Dierenpark Planckendael and in the Leipzig and Berlin Zoo. The scientists report 13 videotaped situations in which particularly bonobo mothers shook their head when they were trying to inhibit or terminate some particular behaviour of their infant. In one example an infant was trying to climb a nearby tree trunk, but her mother pulled her back. The infant continued to try to climb the trunk till eventually the mother seized her infant by the leg and shook her head while looking toward her. However, the infant kept continuing towards the trunk, so after a while the mother pulled her back again, looked at her and shook her head once more. In another episode an infant was manipulating a piece of leek. The mother took the leek from her infant and threw it away. However, the infant recaptured the leek and while trying to take the leek from her infant the mother shook her head twice and threw the leek away again. The video of this last example, observed in the Leipzig Zoo, can be seen on the BBC Earth News website and a larger video on the National Geographic website. Further situations of head-shaking that are reported in the Primates article are the following. In one instance an adult male bonobo shook his head after an infant reached for the male’s food, and in another situation a mother showed head-shaking after an adult female took food away from her.
The researchers mention that the preventive communicative function of the bonobo headshaking expands the variety of motives underlying the use of gestures in great apes. They conclude, however, that further data are necessary to examine the possibility that head shaking in great apes may be a primitive precursor of the human head shake that expresses negation.
In the sign language projects by Beatrix and Allen Gardner, several chimpanzees were learned signs that were considered negatives, based on signs from the American Sign Language. They were the signs CAN’T (used when the chimpanzee was unable to do a task or answer a question, or refused something), ENOUGH (to stop routine activities such as a signing lesson), and NO. The sign NO was made by shaking the head horizontally from side to side, so this behaviour is similar to the spontaneous bonobo behaviour mentioned above. The Gardners report that their chimpanzees used NO to negate in reply to commands, questions and statements, and in response to human threats to throw snowballs or splash water at the chimpanzee. They also state that the chimpanzees made combinations with NO, such as BATH NO and BED NO (Gardner et al., 1989). Sadly enough, the Gardners’ work on signing chimpanzees is flawed by multiple problems of method and interpretation, one of them being that these observations were not filmed, leaving room for several errors of observation and memory (Rivas, 2003, 2005). In my analysis of the signing chimpanzees’ recent use of signs I found four instances of head-shaking in the videotaped interactions that I examined. These head-shakes were all done by Moja (see her picture on the right). However, when Moja shook her head the context did not suggest that she was protesting or preventing some behaviour from another chimp or human, unlike the clear contextual situations described for the bonobo head-shaking above that do suggest this preventice communicative function.
- de Waal, F. (1982). Chimpanseepolitiek. Amsterdam: Becht.
- Gardner, B.T., Gardner, R.A., & Nichols, S.G. (1989). The shapes and uses of signs in a cross-fostering laboratory. In R.A. Gardner, B.T. Gardner & Th. E. van Cantfort (Eds.), Teaching sign language to chimpanzees (pp. 55-180). Albany: State University of New York Press.
- Kortlandt, A. (1969). Chimpansees. In B. Grzimek (Ed.), Het leven der dieren, Band XI (pp. 14-49). Utrecht: Het Spectrum.
- Rivas, E. (2003). GIMME GIMME GIMME. The recent signing behaviour of chimpanzees (Pan troglodytes) in interactions with longtime human companions. Unpublished doctoral dissertation. Nijmegen, the Netherlands: Katholieke Universiteit Nijmegen.
- Rivas, E. (2005). Recent use of signs by chimpanzees (Pan troglodytes) in interactions with humans. Journal of Comparative Psychology, 119, 404-417.
- Schneider, C., Call, J., & Liebal, K. (2010). Do bonobos say NO by shaking their head? Primates, 51, 199-202.