Intentional communication: solving methodological issues to assigning first-order intentional signalling

Intentional signalling plays a fundamental role in human communication. Mapping the taxonomic distribution of comparable capacities may thus shed light on the selective pressures that enabled the evolution of human communication. Nonetheless, severe methodological issues undermine comparisons among studies, species and communicative modalities. Here, we discuss three main obstacles that hinder comparative research of 'first-order' intentional signalling (i.e. voluntary signalling in pursuit of a cognitively represented goal): (i) inconsistency in how behavioural hallmarks are defined and operationalised, (ii) testing of behavioural hallmarks without statistical comparison to control conditions, and (iii) bias against the publication of negative results. To address these obstacles, we present a four-step scheme with 20 statistical operational criteria to distinguish between non-intentional and first-order intentional signalling. Our unified scheme applies to visual and audible signals, thereby validating comparison across communicative modalities and species. This, in turn, promotes the generation and testing of hypotheses about the evolution of intentional communication.

Automated summary

Intentional signalling is crucial in human communication, and studying the taxonomic distribution of this ability may provide insights into the selective pressures that drove the evolution of communication. However, methodological issues such as inconsistent definitions, incomplete testing, and publication bias hinder comparative research in this field. A unified scheme with statistical criteria has been proposed to address these obstacles and allow for comparisons across modalities and species.