Condition-dependent trade-offs maintain honest signaling: A laboratory experiment

How and why animals and humans signal reliably is a key issue in biology and social sciences. For many years the dominant paradigm in biology was the Handicap Principle. It claims a causal relationship between honesty and signal cost and thus predicts that honest signals have to be costly to produce. However, contrary to the Handicap Principle, game theoretical models predict that honest signaling is maintained by condition dependent signaling trade-offs and honest signals need not be costly at the equilibrium. Due to the difficulties of manipulating signal cost and signal trade-offs there is surprisingly little evidence to test these predictions either from biology or from social sciences. Here we conduct a human laboratory experiment with a two-factorial design to test the role of equilibrium signal cost vs. signalling trade-offs in the maintenance of honest communication. We have found that the trade-off condition has much higher influence on the reliability of communication than the equilibrium cost condition. The highest level of honesty was observed in the condition dependent trade-off condition as predicted by recent models. Negative production cost, i.e. fix benefit-contrary to the prediction of the Handicap Principle-promoted even higher level of honesty than the other type of costs under this condition.