Animal linguistics in the making: the Urgency Principle and titi monkeys’ alarm system

Abstract

The emergent field of animal linguistics applies linguistics tools to animal data in order to investigate potential linguistic-like properties of their communication. One of these tools is the “Urgency Principle”, a pragmatic principle stating that in an alarm sequence, calls providing information about the nature or location of a threat must come before those that do not. This theoretical principle has helped understand the alarm system of putty-nosed monkeys, but whether it is relevant for animal communication systems more generally remains to be tested. Moreover, while animal communication systems can convey information via a large set of encoding mechanisms, the Urgency Principle was developed for only one encoding mechanism, call ordering. Here, we propose to extend this principle to other encoding mechanisms and empirically test this with the alarm call system of black-fronted titi monkeys (Callicebus nigrifrons). We investigated how information about the context of emission unfolded with the emission of successive calls. Specifically, we analysed how contextual parameters influenced the gradual sequential organization of the first 50 calls in the sequence, using methods borrowed from computational linguistics and random forest algorithms. We hypothesized that, if the extended Urgency Principle reflected the sequential organization of titi monkey alarm call sequences, mechanisms encoding urgent information about the predatory situation should appear before encoding mechanisms that do not. Results supported the hypothesis that mechanisms encoding for urgent information relating to a predator event consistently appeared before mechanisms encoding for less-urgent social information. Our study suggests that the extended Urgency Principle applies more generally to animal communication, demonstrating that conceptual tools from linguistics can successfully be used to study nonhuman communication systems.

KEY WORDS:

• Callicebus nigrifrons
• vocalisations
• sequences
• computational linguistics
• formal linguistics

ACKNOWLEDGEMENTS

The authors thank Philippe Schlenker and Emmanuel Chemla for helpful discussions, the many field assistants and master students who took part into data collection, and the Santuário do Caraça for their logistic support.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the authors.

ETHICAL STANDARD

The research reported in this article was conducted in compliance with all relevant local and international laws. The 2008-2010 data collection was approved by the University of St Andrews Psychology Ethics Board, the 2014-2016 data collection was approved by the ethical committee CEUA/UNIFAL (number 665/2015).

AUTHOR CONTRIBUTION

L. Narbona Sabaté: conceptualization, data curation, data analysis, writing original draft, editing and revision; G. Mesbahi: conceptualization, data analysis, editing and revision; G. Dezecache: redaction of the original draft, editing and revision; C. Cäsar: data collection, data curation, editing and revision; K. Zuberbühler: funding acquisition, editing and revision; M. Berther: conceptualization, data collection, data curation, data analysis, writing original draft, editing and revision, supervision.

SUPPLEMENTAL DATA

Supplemental data for this article can be accessed at https://doi.org/10.1080/03949370.2021.2015452

DATA ACCESSIBILITY

The full dataset and the associated statistical scripts are available on a Figshare depository (https://figshare.com/projects/Animal_linguistics_inthe_making_The_Urgency_Principle_and_titi_monkeys_alarm_system/121914).

Additional information

Funding

This work received funding from the European Research Council under the European Union’s Seventh Framework Programme [FP7/2007–2013]/ERC grant agreement no. 283871 (PI: K. Zuberbühler), the Swiss National Science Foundation and the University of Neuchâtel, the European Research Council (ERC) under the European Union’s Seventh Framework Programme [FP/2007-2013]/ERC Grant Agreement N°324115–FRONTSEM (PI: P. Schlenker), the European Union’s Horizon 2020 research and innovation programme (grant agreement No. H2020 European Research Council 788077, Orisem, PI: P. Schlenker), from the Fyssen Foundation (post-doc grant) and from the Institut d’Études Cognitives, École Normale Supérieure − PSL Research University supported by grants ANR-10-IDEX-0001-02 and FrontCog ANR-17-EURE-0017. We acknowledge the support received from the Agence Nationale de la Recherche of the French government through the program “Investissements d’Avenir” (16-IDEX-0001 CAP 20-25); FP7 Ideas: European Research Council [283871,324115]; Fondation Fyssen; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung; Université de Neuchâtel.