Honesty in signalling games is maintained by trade-offs rather than costs

16 January, 2023
New publication of Szabolcs Számadó with co-authors

The article „Honesty in signalling games is maintained by trade-offs rather than costs” by Szabolcs Számadó, István Zachar, Dániel Czégel and Dustin J. Penn has been published in BMC Biology.

Available online here: Számadó, S., Zachar, I., Czégel, D. et al. Honesty in signalling games is maintained by trade-offs rather than costs. BMC Biol 21, 4 (2023). https://doi.org/10.1186/s12915-022-01496-9


Signal reliability poses a central problem for explaining the evolution of communication. According to Zahavi’s Handicap Principle, signals are honest only if they are costly at the evolutionary equilibrium; otherwise, deception becomes common and communication breaks down. Theoretical evaluations of the Handicap Principle are difficult, however, because finding the equilibrium cost function in such signalling games is notoriously complicated. Here, we provide a general solution to this problem and show how cost functions can be calculated for any arbitrary, pairwise asymmetric signalling game at the evolutionary equilibrium.
Our model clarifies the relationship between signalling costs at equilibrium and the conditions for reliable signalling. It shows that these two terms are independent in both additive and multiplicative models, and that the cost of signalling at honest equilibrium has no effect on the stability of communication. Moreover, it demonstrates that honest signals at the equilibrium can have any cost value, even negative, being beneficial for the signaller independently of the receiver’s response at equilibrium and without requiring further constraints. Our results are general and we show how they apply to seminal signalling models, including Grafen’s model of sexual selection and Godfray’s model of parent-offspring communication. We argue that the evolution of reliable signalling is better understood within a Darwinian life-history framework, and that the conditions for honest signalling are more clearly stated and understood by evaluating their trade-offs rather than their costs per se.