Honesty needs no cost: beneficial signals can be honest and evolutionarily stable

Abstract

How and why animals communicate honestly is a key issue in biology. The role of signal cost is strongly entrenched in the maintenance in honest signalling. The handicap principle claims that honest signals have to be costly at the equilibrium and this cost is a theoretical necessity. The handicap principle further claims that signalling is fundamentally different from any other adaptation because honest signalling would collapse in the absence of cost. Here I investigate this claim in simple action-response game where signals do not have any cost, instead they have benefits. I show that such beneficial signals can be honest and evolutionarily stable. These signals can be beneficial to both high and low-quality signallers independently of the receivers response, yet they can maintain honest signalling just as much as costly signals. Signal cost-at or out of equilibrium-is not a necessary condition of honesty. Benefit functions can maintain honest signalling as long as the marginal cost-loss of benefit-is high enough for potential cheaters.