A new article published in Proceedings B investigated linguistic laws used in gestural communication of chimpanzees. The first author of the paper, PhD student Raphaela Heeson from the Université de Neuchâtel explained more about the interesting findings of the study and shared her experience of publishing in Proceedings B.
What were the important findings of your study?
Human languages are characterised by common statistical patterns, known as linguistic laws. For example, Zipf’s law of abbreviation states that more commonly used words tend to be shorter, and Menzerath’s law states that larger constructs tend to be made up of shorter constituent parts (e.g. words with more syllables have, on average, shorter syllable lengths). Work on animal vocal communication has indicated that humans are not the only species whose communicative system is underpinned by these laws. In our paper, we show for the first time that these laws also hold in animal gestural communication. Our study focussed on the gestures used in the context of play by a community of wild chimpanzees in Budongo Forest Reserve, Uganda. Chimpanzees’ gestural repertoire has been well documented and in this study we were able to distinguish fifty-eight different gesture types used in the context of social play (examples are given in images 1 and 2).
Analysing the duration of these gestures from video recordings, we found that more frequently used gestures were shorter in duration – following the pattern predicted by Zipf’s law of abbreviation. As examples, video 1 shows a short gesture – “stomp” – that is used relatively frequently, while video 2 shows a long gesture – “arm shake” -that is used relatively infrequently. Looking at sequences of gestures, we also found that – in agreement with Menzerath’s law – longer sequences contain on average shorter gestures. Overall, these results show that primate gestural communication and human language share some fundamental mathematical properties, and that linguistic laws may apply beyond the vocal modality of communication.
Tell us more about yourself?
This study was conducted during my Masters of Research (MRes) in Primate, Biology, Behaviour and Conservation at University of Roehampton in London. The paper is co-authored by my MRes supervisor Prof. Stuart Semple, Dr Cat Hobaiter who collected the original videos of chimpanzee gestures, and Prof. Ramon Ferrer-i-Cancho who provided expert input for statistical analyses. Since completing this work, I have become fascinated by the flexibility and complexity of great ape communication. In my PhD, I am currently looking at how bonobos and chimps use gestures to coordinate joint action – defined as an activity carried out by two or more individuals collaborating to achieve a common goal. With my research, I hope to contribute to our general understanding of how human interaction became as complex as it is today. Perhaps we’re not that special after all?
What was your experience like submitting your paper to Proceedings B?
I experienced the submission with Proceedings B as very orderly, efficient and user-friendly throughout from initial submission until final edits on the proof version.
Proceedings B is looking to publish more high quality research articles and reviews covering the field of animal behaviour. If you have an idea for a review, we strongly encourage you to submit a proposal by completing our proposal template and sending it to the journal. More information about the journal and the submission process can be found on our website.
1 – Infant chimpanzee using a “reach” gesture during play – Dr Catherine Hobaiter, University of St. Andrews, UK.
2 – Juvenile chimpanzee using a “somersault” gesture and play-face to invite for play – Dr Catherine Hobaiter, University of St. Andrews, UK.