Editing Handicap principle (section)

{{good article}}
{{Short description|Hypothesis in evolutionary biology}}
[[File:Peacock Flying.jpg|thumb|300px|right|The peacock tail in flight, a classic example of what [[Amotz Zahavi]] proposed was a handicapped signal of male quality.<ref name="Grafen 1990"/>|alt=Photo of a peacock with its enormous tail]]

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 [[Signalling theory|"honest" or reliable signalling]] between male and female animals which have an obvious motivation to bluff or deceive each other.<ref name="Zahavi 1975 pp. 205–214">{{cite journal |last=Zahavi |first=Amotz |author-link=Amotz Zahavi |title=Mate selection—A selection for a handicap |journal=Journal of Theoretical Biology |publisher=Elsevier BV |volume=53 |issue=1 |year=1975 |issn=0022-5193 |doi=10.1016/0022-5193(75)90111-3 |pages=205–214|pmid=1195756 |bibcode=1975JThBi..53..205Z }}</ref><ref name="Zahavi 1977 pp. 603–605">{{cite journal |last=Zahavi |first=Amotz |author-link=Amotz Zahavi |title=The cost of honesty |journal=Journal of Theoretical Biology |publisher=Elsevier BV |volume=67 |issue=3 |year=1977 |issn=0022-5193 |doi=10.1016/0022-5193(77)90061-3 |pages=603–605|pmid=904334 |bibcode=1977JThBi..67..603Z }}</ref><ref name="Zahavi Zahavi 1997">{{cite book |last1=Zahavi |first1=Amotz |author1-link=Amotz Zahavi |last2=Zahavi |first2=Avishag |title=The handicap principle: a missing piece of Darwin's puzzle |publisher=Oxford University Press |location=New York |year=1997 |isbn=978-0-19-510035-8 |oclc=35360821 |url=http://eprints.soton.ac.uk/261475/1/10.1.1.40.3266.pdf}}</ref> 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 [[fitness (biology)|biological fitness]] signal this through handicapping [[ethology|behaviour]], or [[Morphology (biology)|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.<ref name="Davis 1976" /><ref name="Eshel 1978" /><ref name="Kirkpatrick 1986" /><ref name="Pomiankowski 1987" /><ref name="Maynard Smith 1976" />   

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.