Overlooked evidence for semantic compositionality and signal reduction in wild chimpanzees (Pan troglodytes)

Petar Gabrić

doi:10.1007/s10071-021-01584-3

Abstract

Recent discoveries of semantic compositionality in Japanese tits have enlivened the discussions on the presence of this phenomenon in wild animal communication. Data on semantic compositionality in wild apes are lacking, even though language experiments with captive apes have demonstrated they are capable of semantic compositionality. In this paper, I revisit the study by Boesch (Hum. Evol. 6:81–89, 1991) who investigated drumming sequences by an alpha male in a chimpanzee (Pan troglodytes) community in the Taï National Park, Côte d’Ivoire. A reanalysis of the data reveals that the alpha male produced semantically compositional combined messages of travel direction change and resting period initiation. Unlike the Japanese tits, the elements of the compositional expression were not simply juxtaposed but displayed structural reduction, while one of the two elements in the expression coded the meanings of both elements. These processes show relative resemblance to blending and fusion in human languages. Also unlike the tits, the elements of the compositional expression did not have a fixed order, although there was a fixed distribution of drumming events across the trees used for drumming. Because the elements of the expression appear to carry verb-like meanings, the compositional expression also resembles simple verb-verb constructions and short paratactic combinations of two clauses found across languages. In conclusion, the reanalysis suggests that semantic compositionality and phenomena resembling paratactic combinations of two clauses might have been present in the communication of the last common ancestor of chimpanzees and humans, not necessarily in the vocal modality.

Highlights

Language evolution is a hotly debated topic
I revisit the study by Boesch (1991) who investigated drumming behavior by an alpha male in a community of wild chimpanzees (Pan troglodytes), with the aim of demonstrating for the first time that one of the fundamental linguistic phenomena—the ability to combine meaningful elements—is present in wild chimpanzee communication
It is interesting that the semantic compositionality of Brutus’s communication was observed in a foraging context, as previous discussions have proposed that the complexity of some hunting behaviors in extinct hominins might be an indicator of linguistic communication in these species/populations (e.g., Botha 2020), possibly suggesting an association between subsistence strategies and food acquisition, and the emergence of more complex communication

Summary

Introduction

Language evolution is a hotly debated topic. our ability to investigate it is severely limited due to a multitude of factors, most prominently the lack of valid methods and techniques. By arranging the words in the given manner, the different parts of the utterance are assigned, among other functions, different semantic roles: John is the agent (the one performing an action), broke is the predicate (in this case, the action), while the glass is the patient (the object on which the action is being performed) By combining these elements in a sentence using specific rules (such as word order in this case) can the compositional meaning of an agent-action-patient event be transparently coded and transmitted. Approaching and scanning behaviors in response to ABC-D and D-ABC5 This constitutes tentative evidence for semantic compositionality in Japanese tits because (1) the compositional message ABC-D consists of two elements for both of which it has been observed are meaningful when used individually and because (2) there seems to be a specific rule (something like ABC before D) governing how this particular compositional message should be coded (and decoded). The present paper analyses 22 observations which can be classified into three categories: 2A, 1A + 1B, and 1A + 2B/2A + 1B

Background

Findings

Conclusion