Gelada vocal sequences follow Menzerath's linguistic law.
Identifying universal principles underpinning diverse natural systems is a key goal of the life sciences. A powerful approach in addressing this goal has been to test whether patterns consistent with linguistic laws are found in nonhuman animals. Menzerath's law is a linguistic law that states that, the larger the construct, the smaller the size of its constituents. Here, to our knowledge, we present the first evidence that Menzerath's law holds in the vocal communication of a nonhuman species. We show that, in vocal sequences of wild male geladas (Theropithecus gelada), construct size (sequence size in number of calls) is negatively correlated with constituent size (duration of calls). Call duration does not vary significantly with position in the sequence, but call sequence composition does change with sequence size and most call types are abbreviated in larger sequences. We also find that intercall intervals follow the same relationship with sequence size as do calls. Finally, we provide formal mathematical support for the idea that Menzerath's law reflects compression-the principle of minimizing the expected length of a code. Our findings suggest that a common principle underpins human and gelada vocal communication, highlighting the value of exploring the applicability of linguistic laws in vocal systems outside the realm of language.
Department of Psychology, University of Michigan, Ann Arbor, MI 48109; gustison@umich.edu.
Morgan L
ML
Gustison
Centre for Research in Evolutionary, Social and Interdisciplinary Anthropology, University of Roehampton, London SW15 4JD, United Kingdom;
Stuart
S
Semple
Complexity and Quantitative Linguistics Laboratory, Laboratory for Relational Algorithmics, Complexity, and Learning Research Group, Departament de Ciències de la Computació, Universitat Politècnica de Catalunya, 08034 Barcelona, Catalonia, Spain;
Ramon
R
Ferrer-I-Cancho
Department of Psychology, University of Michigan, Ann Arbor, MI 48109; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109.
Thore J
TJ
Bergman
D000465:Algorithms; D000818:Animals; D008037:Linguistics; D008297:Male; D008954:Models, Biological; D012737:Sex Factors; D013018:Sound Spectrography / Q000379:methods*; D013068:Speech Production Measurement / Q000379:methods; D016671:Theropithecus / Q000502:physiology*; D014828:Vocalization, Animal / Q000502:physiology*
Menzerath; Zipf; communication; language; primate