Optionality in animal communication: a novel framework for examining the evolution of arbitrariness

Abstract

A critical feature of language is that the form of words need not bear any perceptual similarity to their function -these relationships can be 'arbitrary'. The capacity to process these arbitrary formfunction associations facilitates the enormous expressive power of language. However, the evolutionary roots of our capacity for arbitrariness, i.e. the extent to which related abilities may be shared with animals, is largely unexamined. We argue this is due to the challenges of applying such an intrinsically linguistic concept to animal communication, and address this by proposing a novel conceptual framework highlighting a key underpinning of linguistic arbitrariness, which is nevertheless applicable to non-human species. Specifically, we focus on the capacity to associate alternative functions with a signal, or alternative signals with a function, a feature we refer to as optionality. We apply this framework to a broad survey of findings from animal communication studies and identify five key dimensions of communicative optionality: signal production, signal adjustment, signal usage, signal combinatoriality and signal perception. We find that optionality is widespread in non-human animals across each of these dimensions, although only humans demonstrate it in all five. Finally, we discuss the relevance of optionality to behavioural and cognitive domains outside of communication. This investigation provides a powerful new conceptual framework for the cross-species investigation of the origins of arbitrariness, and promises to generate original insights into animal communication and language evolution more generally.

Innovative multi-material tool use in the pant-hoot display of a chimpanzee

“…Production of vocal behaviour in primates has been argued by some researchers to be strictly governed by internal arousal states, in large part due to the finding that apes are lacking key neural circuitry which is known to be important for the voluntary control of vocal production in humans 52 – 54 . However, there is also a growing body of evidence demonstrating hitherto unsuspected flexibility in the vocal behaviour of apes 51 , 55 , 56 , to which EH’s tub-stacking behaviour may contribute a further data point. Specifically, we suggest that because in three out of four observations of a completed tub-stack (Videos 1 – 4 ) EH initiated vocal production after the condition of a completed tub-stack is satisfied, this indicates that they possessed some degree of control over the moment of deployment of a pant-hoot display.…”

What made us “hunter-gatherers of words”

“…It made it possible for words to be detached from the bounds of reality (truth, reference), thereby allowing for human language to achieve a level of flexibility and creativity (world-making) that makes our system of communication and thought quite special. In other words, self-domestication created an ecology that made it possible for users (learners, communicators) to abandon the need to rely on “credible signaling” (an important function of past communicative systems, Mehr et al, 2021 ), in effect allowing them to suspend their disbelief in the face of “honest fakes,” and setting the stage for the strongest meaning of “arbitrary” signals in the sense of Planer and Kalkman ( 2020 ) (see also Gasparri et al, 2022 ; Watson et al, 2022 ). I thus concur with Rossano ( 2010 ) that social factors were critical in the evolutionary emergence of symbolism, but disagree with him that symbols impose special cognitive demands.…”

Loquens : A characterization of “Hunter-Gatherers of Words”

“…It made it possible for words to be detached from the bounds of reality (truth, reference), thereby allowing for human language to achieve a level of creativity that makes is quite special. In other words, self-domestication created an ecology that made it possible for users (learners, communicators) to abandon the need to rely on "credible signaling" (an important function of past communicative systems, Mehr et al (2021)), in effect allowing them to suspend their disbelief in the face of "honest fakes", and setting the stage for the strongest meaning of "arbitrary" signals in the sense of Planer and Kalkman (2020) (see also Watson et al (2022)). I thus concur with Rossano (2010) that social factors were critical in the evolutionary emergence of symbolism, but disagree with him that symbols imposes special cognitive demands.…”