A novel study by researchers from Scotland, Germany, Switzerland and Uganda compared gestures made by non-human apes and human infants (aged 11–21 months). The researchers proposed that while previous studies have investigated facial and vocal expressions in non-human apes and humans, no study has actually compared gesture in human and non-human primates. We have considerable knowledge therefore, about the repertoire of gestures from non-human apes, but little from the human species.
Investigating gesture in apes
Human infants were selected as the comparison group under investigation as they do not yet rely on language as their primary form of communication. Further, infants from two different cultural groups (German and Ugandan) were included in the study in order to reduce the possibility of bias emerging from culture and native language which has been shown in previous studies to influence gesture.
In order to generate data that allowed direct comparison between non-human apes and human infants, a methodology that has been commonly employed across the non-human ape species was adopted. Data for non-human apes observed in their natural habitat (the Budongo Forest in Uganda) was compared to that observed for human infants either at home or at a daytime childcare facility (considered their natural habitats). Recordings of all social interactions were made, analysed and coded to identify intentional communications based on gesture (any vocalisations were ignored). Intentional communication was defined based on the work of Hobaiter and Byrne (2011)1.
More in common than we might think
A total of 788 potential gestures by the infants were identified and classified into 52 gestural types of which 50 were found to be in common with the non-human ape species; 46 of the 52 gestures were also demonstrated by chimpanzees and of the remaining six, four were present in the gestural repertoire of gorillas. Surprisingly, only two gestures, arm bend and hand wave, were found to be specific to human infants. As well as the actual gestures, the pattern of use of gestures was indeed similar between non-human apes and human infants; for example, using gestures singularly as well as in rapid sequence without a pause, or with a pause where their initial gestures appeared to fail. Of course some differences were also found such as the pointing gesture which was more likely to be used by human infants.
While the study is based on a small sample size (13 human infants) and the authors suggest caution in interpretation, they also pose the possibility that many of the gestures identified are a part of a universal series of gestures used for communication by both human and non-human primates. As a result the repertoire of gestures may be innate with human infants demonstrating these consistently prior to language taking over as their primary form of social communication. Future research with a larger sample of children will provide more clarity with regard to these intriguing findings.
doi.org/10.1007/s10071-018-1213-z
1 Hobaiter, C. & Byrne, R.W. (2011). The gestural repertoire of the wild chimpanzee. Anim Cognit, 14, 745-767.
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