Grand Challenge — Honest Signals, Costly Lies: Trust, Deception, and the Evolution of Communication

From spider dances to human language, communication systems face the same fundamental problem: why should anyone believe a signal when deception can pay? Signalling theory tells us that honesty has to be enforced — by cost, by context, or by something deeper in the architecture of communication itself. In this session, we explore how trust became a design feature of human language, how multimodality keeps signals honest across species, and what these evolutionary perspectives reveal about deception, cooperation, and communication today.

Hosted by Jonas Nölle.

Talk 1 — The Platform of Trust as a Deep Design Principle for Language Origins (Sławomir Wacewicz)

The honesty problem in communication is well known: cheap signals are vulnerable to deception, manipulation, and receiver resistance. It follows that language-like communication presupposes a prior interactional infrastructure that stabilises honesty sufficiently for low-cost signals to scale. In language origins research, however, the full theoretical consequences of this problem are still often underplayed. As a result, I argue, many supposedly “evolutionary” models of language origins remain merely gradualistic or accretive: they describe how more language-like capacities are added over time, without fully embedding language in a general theory of the evolution of communication, such as signalling theory.

In this talk, I present the platform of trust as a starting point for theorising language origins. PoT is a socio-ecological niche in which communication can be cheap, honest, large-scale, and extended beyond kin because receivers tend to trust messages as a default. I will argue that the flipping of this default setting — from expecting manipulation to expecting honesty — is the central breakthrough in language origins, with cascading downstream consequences. Once this shift is taken seriously, many familiar features of language, including several of Hockett’s design features, can be reinterpreted as consequences of trust-based communicative efficiency. I will illustrate this with pantomime: signalling theory predicts two distinct types of pantomime, with two different evolutionary trajectories — “expensive hype” pantomime, as found in ritual and performance, and “efficient whispers” pantomime, which naturally simplifies into communicatively effective manual gestures and signs.

Talk 2 — Multimodality as a safeguard of honesty in communication and language: from Animals to Humans (Severine Hex)

Multimodality characterizes nearly every communicative system, and in our recent paper accepted in Behavioral and Brain Sciences we argue that this feature of communication plays an essential evolutionary role in safeguarding signal honesty. We first discuss the importance of honesty in communication broadly, and introduce socially-mediated controls as an alternative to intrinsic costs. We next outline how multimodality mitigates signal dishonesty, and highlight the importance of signal honesty in complex, cooperative species, such as humans, wherein acceptance may incentivize dishonesty. Finally, we urge researchers to investigate the role of multimodality and honesty in cooperative, “cheap” signals, emphasizing the need for comparative work on the forces that have shaped the evolution of communication.

Speakers

Sławomir Wacewicz (Nicolaus Copernicus University in Toruń) is an Associate Professor of Linguistics. He is co-founder of the Centre for Language Evolution Studies (CLES), where he currently serves as deputy head. He also directs the Toruń Interactionist Lab (TIL), which investigates the dynamics of human interaction. His work on the cost-benefit calculus of communication has contributed to current debates on language origins, especially through the notion of a “platform of trust” as a foundational condition for the evolution of cheap, open-ended human communication.

Severine Hex (University of Exeter; Junior Fellow, Harvard Society of Fellows) is a comparative ethologist. She studies how animals in complex societies use multimodal communication and social bonds to navigate their social worlds. She will present her new BBS target article, “Multimodality as a safeguard of honesty in communication and language: from Animals to Humans”, which argues that combining signals across modalities is one of evolution’s key solutions to the honesty problem — from animal displays to human language.