The investigation of linguistic laws is a cornerstone of quantitative linguistics.

In recent years, studies have begun to explore the universality of linguistic laws beyond our own species, and those works have provided important insights into the basic rules of organization underpinning natural information systems.

A team of researchers led by University of Roehampton’s Professor Stuart Semple looked at two particular linguistic laws: Zipf’s law of abbreviation, which predicts that more commonly used words tend to be shorter, and Menzerath’s law, which predicts that larger linguistic structures are made up of shorter parts (e.g. longer words are made up of shorter syllables).

While these laws are known to hold in many different languages, they had never previously been explored in the gestural communication of animals.

In the study, the researchers studied videos of gestures made by wild chimpanzees living in Uganda’s Budongo Forest Reserve.

They focused on gesturing during play as this is a context where they are most frequently used, both alone and in sequences.

They measured the length of over 2,000 play gestures, of 58 different types, and found that — just as predicted by the two linguistic laws — more frequently used gestures were shorter in duration, and in longer sequences, the average gesture duration was also shorter.

“Primate gestural communication is, of course, very different to human language, but our results show that these two systems are underpinned by the same mathematical principles,” said study first author Raphaela Heesen, a student at the University of Roehampton.

“We hope that our work will pave the way for similar studies, to see quite how widespread these laws might be across the animal kingdom.”