Handicap principle

The handicap principle is a hypothesis proposed by the Israeli biologist Amotz Zahavi in 1975. It is meant to explain how "signal selection" during mate choice may lead to "honest" or reliable signalling between male and female animals which have an obvious motivation to bluff or deceive each other. The handicap principle suggests that secondary sexual characteristics are costly signals which must be reliable, as they cost the signaller resources that individuals with less of a particular trait could not afford. The handicap principle further proposes that animals of greater biological fitness signal this through handicapping behaviour, or morphology that effectively lowers overall fitness. The central idea is that sexually selected traits function like conspicuous consumption, signalling the ability to afford to squander a resource. Receivers then know that the signal indicates quality, because inferior-quality signallers are unable to produce such wastefully extravagant signals. The handicap principle is supported by game theory modelling representing situations such as nestlings begging for food, predator-deterrent signalling, and threat displays. However, honest signals are not necessarily costly, undermining the theoretical basis for the handicap principle, which remains unconfirmed by empirical evidence.