Editing Signalling theory (section)

== Human honest signals ==

{{further|Costly signaling theory in evolutionary psychology}}
Human behaviour may also provide examples of costly signals. In general, these signals provide information about a person's phenotypic quality or cooperative tendencies. Evidence for costly signalling has been found in many areas of human interaction including risk-taking, hunting, and religion.{{sfn|Bliege Bird|Smith|Bird|2001}}

=== Costly signalling in hunting ===

[[File:Kalina hunter gatherer.jpg|thumb|left|A male hunter and a female gatherer of the [[Kalina people|Kali'na people]] of Guyana, drawn by [[Pierre Barrère]] in 1743. Generous sharing by male hunters may serve as a "costly signal", helping them to acquire mates.]]

Large game hunting has been studied extensively as a signal of men's willingness to take physical risks, as well as showcase strength and coordination.{{sfn|Bliege Bird|Smith|Bird|2001}}{{sfn|Gurven|Hill|2009}}{{sfn|Hawkes|1990}}{{sfn|Wiessner|2002}} Costly signalling theory is a useful tool for understanding food sharing among [[hunter gatherers]] because it can be applied to situations in which [[Reciprocity (cultural anthropology)|delayed reciprocity]] is not a viable explanation.{{sfn|Bliege Bird|Bird|1997}}{{sfn|Gurven|Hill|Hurtado|Lyles|2000}}{{sfn|Hawkes|1993}} Instances that are particularly inconsistent with the delayed reciprocity hypothesis are those in which a hunter shares his kill indiscriminately with all members of a large group.{{sfn|Wiessner|1996}} In these situations, the individuals sharing meat have no control over whether or not their generosity will be reciprocated, and [[Free rider problem|free riding]] becomes an attractive strategy for those receiving meat. Free riders are people who reap the benefits of group-living without contributing to its maintenance.{{sfn|Barrett|Dunbar|Lycett|2002}} Costly signalling theory can fill some of the gaps left by the delayed reciprocity hypothesis.{{sfn|Sosis|2000b}}{{sfn|Smith|Bliege Bird|2000}} Hawkes has suggested that men target large game and publicly share meat to draw social attention or to show off.{{sfn|Hawkes|1991}}{{sfn|Hawkes|1993}} Such display and the resulting favorable attention can improve a hunter's reputation by providing information about his phenotypic quality. High quality signallers are more successful in acquiring mates and allies. Thus, costly signalling theory can explain apparently wasteful and [[altruism|altruistic]] behaviour.{{sfn|Zahavi|1975}}{{sfn|Grafen|1990}}{{sfn|Smith|Bliege Bird|2000}}{{sfn|Johnstone|1995}}{{sfn|Johnstone|1997}}{{sfn|Zahavi|1975}}{{sfn|Zahavi|1977}}

In order to be effective, costly signals must fulfill specific criteria.{{sfn|Zahavi|1975}}{{sfn|Bliege Bird|Smith|Bird|2001}}{{sfn|Hawkes|Bliege Bird|2002}} Firstly, signallers must incur different levels of cost and benefit for signalling behaviour. Secondly, costs and benefits must reflect the signallers' [[phenotype|phenotypic]] quality. Thirdly, the information provided by a signal should be directed at and accessible to an audience. A receiver can be anyone who stands to benefit from information the signaller is sending, such as potential mates, allies, or competitors. Honesty is guaranteed when only individuals of high quality can pay the (high) costs of signalling. Hence, [[Handicap principle|costly signals]] make it impossible for low-quality individuals to fake a signal and fool a receiver.{{sfn|Zahavi|1975}}{{sfn|Bliege Bird|Smith|Bird|2001}}{{sfn|Hawkes|Bliege Bird|2002}}
 
Bliege Bird et al. observed turtle hunting and spear fishing patterns in a [[Meriam people|Meriam]] community in the [[Torres Strait]] of Australia, publishing their findings in 2001.<ref>{{cite journal | url=https://academic.oup.com/beheco/article/14/1/116/209182 | doi=10.1093/beheco/14.1.116 | title=The benefits of costly signaling: Meriam turtle hunters | year=2003 | last1=Smith | first1=E. A. | journal=Behavioral Ecology | volume=14 | pages=116–126 | doi-access=free }}</ref><ref>{{Cite thesis |last=Grayson |first=Jillian |title=Characteristics of traditional dugong and green turtle fisheries in Torres Strait: opportunities for management |date=2011 |publisher=James Cook University {{!}} Australia |url=https://researchonline.jcu.edu.au/29585/ |doi=10.25903/r8eh-n255}}</ref> Here, only some Meriam men were able to accumulate high caloric gains for the amount of time spent turtle hunting or spear fishing (reaching a threshold measured in kcal/h). Since a daily catch of fish is carried home by hand and turtles are frequently served at large feasts, members of the community know which men most reliably brought them turtle meat and fish. Thus, turtle hunting qualifies as a costly signal. Furthermore, turtle hunting and spear fishing are actually less productive (in kcal/h) than foraging for shellfish, where success depends only on the amount of time dedicated to searching, so shellfish foraging is a poor signal of skill or strength. This suggests that energetic gains are not the primary reason men take part in turtle hunting and spear fishing.{{sfn|Bliege Bird|Smith|Bird|2001}} A follow-up study found that successful Meriam hunters do experience greater social benefits and reproductive success than less skilled hunters.{{sfn|Smith|Bliege Bird|Bird|2002}}

The [[Hadza people]] of [[Tanzania]] also share food, possibly to gain in reputation.{{sfn|Marlowe|2010}} Hunters cannot be sharing meat mainly to provision their families or to gain reciprocal benefits, as teenage boys often give away their meat even though they do not yet have wives or children, so costly signalling of their qualities is the likely explanation.{{sfn|Hawkes|O'Connell|Blurton_Jones|2001}} These qualities include good eyesight, coordination, strength, knowledge, endurance, or bravery. Hadza hunters more often pair with highly fertile, hard-working wives than non-hunters.{{sfn|Hawkes|Bliege Bird|2002}} A woman benefits from mating with a man who possesses such qualities as her children will most likely inherit qualities that increase fitness and survivorship. She may also benefit from her husband's high social status. Thus, hunting is an honest and costly signal of phenotypic quality.{{sfn|Smith|Bliege Bird|2000}}{{sfn|Hawkes|O'Connell|Blurton Jones|2001}} [[Frank Marlowe|Frank W. Marlowe]]'s ''The Hadza: Hunter-Gatherers of Tanzania'' showed that this data confirms that this is also true within the Hadza, based on the documentation on the [[!Kung]], in Megan Biesele's book on !Kung folklore, ''Women Like Meat''.

Among the men of [[Ifaluk]] atoll, costly signalling theory can also explain why men torch fish.{{sfn|Sosis|2000a}}<ref>{{Cite journal |last=Sosis |first=Richard |date=July 2000 |title=Costly signaling and torch fishing on Ifaluk atoll |url=https://linkinghub.elsevier.com/retrieve/pii/S1090513800000301 |journal=Evolution and Human Behavior |language=en |volume=21 |issue=4 |pages=223–244 |doi=10.1016/S1090-5138(00)00030-1|pmid=10899476 |bibcode=2000EHumB..21..223S |url-access=subscription }}</ref> Torch fishing is a ritualized method of fishing on Ifaluk whereby men use torches made from dried coconut fronds to catch large [[Dogtooth tuna|dog-toothed tuna]]. Preparation for torch fishing requires significant time investments and involves a great deal of organization. Due to the time and energetic costs of preparation, torch fishing results in net caloric losses for fishers. Therefore, torch fishing is a handicap that serves to signal men's productivity.{{sfn|Sosis|2000a}} Torch fishing is the most advertised fishing occupation on Ifaluk. Women and others usually spend time observing the canoes as they sail beyond the reef. Also, local rituals help to broadcast information about which fishers are successful and enhance fishers' reputations during the torch fishing season. Several ritual behaviors and dietary constraints clearly distinguish torch fishers from other men. First, males are only permitted to torch fish if they participate on the first day of the fishing season. The community is well informed as to who participates on this day, and can easily identify the torch fishers. Second, torch fishers receive all of their meals at the canoe house and are prohibited from eating certain foods. People frequently discuss the qualities of torch fishermen. On Ifaluk, women claim that they are looking for hard-working mates.{{sfn|Sosis|Feldstein|Hill|1998}} With the distinct sexual division of labor on Ifaluk, industriousness is a highly valued characteristic in males.{{sfn|Sosis|1997}} Torch fishing thus provides women with reliable information on the work ethic of prospective mates, which makes it an honest costly signal.{{sfn|Smith|Bliege Bird|2000}}

In many human cases, a strong reputation built through costly signalling enhances a man's social status over the statuses of men who signal less successfully.{{sfn|Wiessner|1996}}{{sfn|Kelly|1995}}{{sfn|Dowling|1968}} Among northern [[Kalahari]] foraging groups, traditional hunters usually capture a maximum of two or three antelopes per year.{{sfn|Lee|1979}} It was said of a particularly successful hunter:{{sfn|Thomas|1959}}
 
:"It was said of him that he never returned from a hunt without having killed at least a wildebeest, if not something larger. Hence the people connected with him ate a great deal of meat and his popularity grew."{{sfn|Thomas|1959}}
 
Although this hunter was sharing meat, he was not doing so in the framework of reciprocity.{{sfn|Thomas|1959}} The general model of costly signalling is not reciprocal; rather, individuals who share acquire more mates and allies.{{sfn|Zahavi|1975}}{{sfn|Bliege Bird|Smith|Bird|2001}} Costly signalling applies to situations in Kalahari foraging groups where giving often goes to recipients who have little to offer in return. A young hunter is motivated to impress community members with daughters so that he can obtain his first wife. Older hunters may wish to attract women interested in an extramarital relationship, or to be a [[wikt:co-wife|co-wife]].{{sfn|Lee|1993}}{{sfn|Shostak|1981}} In these northern Kalahari groups, the killing of a large animal indicates a man who has mastered the art of hunting and can support a family. Many women seek a man who is a good hunter, has an agreeable character, is generous, and has advantageous social ties.{{sfn|Lee|1979}}{{sfn|Shostak|1981}}{{sfn|Marshall|1976}} Since hunting ability is a prerequisite for marriage, men who are good hunters enter the marriage market earliest. Costly signalling theory explains seemingly wasteful foraging displays.{{sfn|Hawkes|Bliege Bird|2002}}

=== Physical risk ===
{{anchor|Physical risks as a costly signal}}
[[File:Motorcycle racing.jpg|thumb|Young men may take part in risky sports like [[motorcycle racing]] to signal their strength and skill.]]

Costly signalling can be applied to situations involving physical strain and risk of physical injury or death.{{sfn|Bliege Bird|Smith|Bird|2001}}{{sfn|Farthing|2005}} Research on physical risk-taking is important because information regarding why people, especially young men, take part in high risk activities can help in the development of prevention programs.{{sfn|Nell|2002}}{{sfn|Farthing|2005}} Reckless driving is a lethal problem among young men in western societies.{{sfn|Nell|2002}} A male who takes a physical risk is sending the message that he has enough strength and skill to survive extremely dangerous activities. This signal is directed at peers and potential mates.{{sfn|Zahavi|1975}} When those peers are criminals or [[Gang|gang members]], sociologists [[Diego Gambetta]] and [[James Densley]] find that risk-taking signals can help expedite acceptance into the group.{{sfn|Densley|2012}}{{sfn|Gambetta|2009}}

In a study of risk-taking, some types of risk, such as physical or heroic risk for others' benefit, are viewed more favorably than other types of risk, such as taking drugs. Males and females valued different degrees of heroic risk for mates and same-sex friends. Males valued heroic risk-taking by male friends, but preferred less of it in female mates. Females valued heroic risk-taking in male mates and less of it in female friends. Females may be attracted to males inclined to physically defend them and their children. Males may prefer heroic risk-taking by male friends as they could be good allies.{{sfn|Farthing|2005}}

In western societies, voluntary [[blood donation]] is a common, yet less extreme, form of risk-taking. Costs associated with these donations include pain and risk of infection.{{sfn|Schreiber|Schlumpf|Glynn|Wright|2006}} If blood donation is an opportunity to send costly signals, then donors will be perceived by others as generous and physically healthy.{{sfn|Zahavi|1975}}{{sfn|Lyle|Smith|Sullivan|2009}} In a survey, both donors and non-donors attributed health, generosity, and ability to operate in stressful situations to blood donors.{{sfn|Lyle|Smith|Sullivan|2009}}

=== Religion ===
{{anchor|Religion as a costly signal}}
{{further|Evolutionary psychology of religion}}
[[File:Handling of serpents, a part of the ceremony at the Pentecostal Church of God. This coal camp offers none of the... - NARA - 541340.jpg|thumb|upright|left|Religious rituals such as [[Snake handling in religion|snake handling]] may be explainable as costly signals.]]

Costly religious rituals such as [[genital modification]], [[Fasting|food and water deprivation]], and [[Snake handling in religion|snake handling]] look paradoxical in evolutionary terms. Devout religious beliefs wherein such traditions are practiced appear maladaptive.{{sfn|Tuzin|1982}} Religion may have arisen to increase and maintain intragroup cooperation.{{sfn|Steadman|Palmer|2008}} Cooperation leads to altruistic behaviour,{{sfn|Bulbulia|2004}} and costly signalling could explain this.{{sfn|Zahavi|1975}} All religions may involve costly and elaborate rituals, performed publicly, to demonstrate loyalty to the religious group.{{sfn|Irons|2001}} In this way, group members increase their allegiance to the group by signalling their investment in group interests. However, as group size increases among humans, the threat of free riders grows.{{sfn|Barrett|Dunbar|Lycett|2002}} Costly signalling theory accounts for this by proposing that these religious rituals are costly enough to deter free riders.{{sfn|Iannaccone|1992}}

Irons proposed that costly signalling theory could explain costly religious behaviour. He argued that hard-to-fake religious displays enhanced trust and solidarity in a community, producing emotional and economic benefits. He showed that display signals among the [[Yomut]] [[Iranian Turkmen|Turkmen]] of northern [[Iran]] helped to secure trade agreements. These "ostentatious" displays signalled commitment to Islam to strangers and group members.{{sfn|Irons|1996}} Sosis demonstrated that people in religious communities are four times more likely to live longer than their secular counterparts,{{sfn|Sosis|2000b}}{{sfn|Bulbulia|2004}} and that these longer lifespans were positively correlated with the number of costly requirements demanded from religious community members.{{sfn|Sosis|Bressler|2003}} However, confounding variables may not have been excluded.{{sfn|Hood|Hill|Spilka|2009}} Wood found that religion offers a subjective feeling of well-being within a community, where costly signalling protects against free riders and helps to build self-control among committed members.{{sfn|Wood|2016}} Iannaccone studied the effects of costly signals on religious communities. In a self-reported survey, as the strictness of a church increased, the attendance and contributions to that church increased proportionally. In effect, people were more willing to participate in a church that has more stringent demands on its members.{{sfn|Iannaccone|1992}} Despite this observation, costly donations and acts conducted in a religious context does not itself establish that membership in these clubs is actually worth the entry costs imposed.

Despite the experimental support for this hypothesis, it remains controversial. A common critique is that devoutness is easy to fake, such as simply by attending a religious service.{{sfn|Rees|2009}} However, the hypothesis predicts that people are more likely to join and contribute to a religious group when its rituals are costly.{{sfn|Iannaccone|1992}} Another critique specifically asks: why religion? There is no evolutionary advantage to evolving religion over other signals of commitment such as nationality, as Irons admits. However, the reinforcement of religious rites as well as the intrinsic reward and punishment system found in religion makes it an ideal candidate for increasing intragroup cooperation. Finally, there is insufficient evidence for increase in fitness as a result of religious cooperation.{{sfn|Bulbulia|2004}} However, Sosis argues for benefits from religion itself, such as increased longevity, improved health, assistance during crises, and greater psychological well-being,{{sfn|Sosis|2003}} although both the supposed benefits from religion and the costly-signaling mechanism have been contested.{{sfn|Schuurmans-Stekhoven|2016}}

=== Language ===
Some scholars view the emergence of language as the consequence of some kind of social transformation<ref name="Knight Power 2012">{{Cite book| last1=Knight| first1=Chris| last2=Power| first2=Camilla| title=Social conditions for the evolutionary emergence of language| editor=Maggie Tallerman |editor2=Kathleen R. Gibson| work=The Oxford handbook of language evolution| year=2012| publisher=Oxford University Press| location=Oxford; New York
| isbn=978-0-19-954111-9 | oclc=724665645 | pages=346–49 | url=http://www.chrisknight.co.uk/wp-content/uploads/2007/09/Knight-Power-Social-Conditions1.pdf}}</ref> that, by generating unprecedented levels of public trust, liberated a genetic potential for linguistic creativity that had previously lain dormant.<ref name="Rappaport 1999">{{cite book | last=Rappaport | first=Roy | title=Ritual and religion in the making of humanity | publisher=Cambridge University Press | location=Cambridge, U.K. New York | year=1999 | isbn=9780521296908 | oclc=848728046}}</ref><ref name="Knight 2008">{{cite journal | last1=Knight | first1=C. | year=2008 | title='Honest fakes' and language origins | url=http://www.chrisknight.co.uk/wp-content/uploads/2007/09/JCS_Knight_CRC.pdf | journal=Journal of Consciousness Studies | volume=15 | issue=10–11| pages=236–48}}</ref><ref name="Knight 2010">{{Cite book | last1=Knight | first1=Chris| title=The origins of symbolic culture|editor1=Ulrich J Frey |editor2=Charlotte Störmer |editor3=Kai P Willführ | work=Homo novus : a human without illusion | year=2010 | publisher=Springer | location=Berlin; New York | isbn=978-3-642-12141-8 | oclc=639461749| pages=193–211 | url=http://www.chrisknight.co.uk/wp-content/uploads/2007/09/The-Origins-of-Symbolic-Culture.pdf}}</ref> "Ritual/speech coevolution theory" views rituals as costly signals that ensures honesty and reliability of language communication.<ref name="Knight 1998">{{Cite book| last1=Knight| first1=Chris| title=Ritual/speech coevolution: a solution to the problem of deception|editor1=James R Hurford |editor2=Michael Studdert-Kennedy |editor3=Chris Knight | work=Approaches to the evolution of language : social and cognitive base | year=1998 | publisher=Cambridge University Press | location=Cambridge, UK; New York | isbn=978-0-521-63964-4 | oclc=37742390 | pages=68–91 | url=http://www.chrisknight.co.uk/wp-content/uploads/2007/09/knight_ritual_speech_coevolution.pdf}}</ref><ref name="Knight 2006">{{Cite book | last1=Knight | first1=Chris| title=Language co-evolved with the rule of law |editor1=Angelo Cangelosi |editor2=Andrew D M Smith |editor3=Kenny Smith | work=The evolution of language : proceedings of the 6th international conference (EVOLANG6), Rome, Italy, 12–15 April 200 | year=2006 | publisher=World Scientific Publishing| location=New Jersey | isbn=978-981-256-656-0 | oclc=70797781 | url=http://www.chrisknight.co.uk/wp-content/uploads/2008/01/knight-springer-online-fulltext.pdf | pages=168–175}}</ref> Scholars in this intellectual camp argue that even [[Common chimpanzee|chimpanzee]]s and [[bonobo]]s have latent symbolic capacities that they rarely—if ever—use in the wild. Objecting to the sudden mutation idea, these authors state that even if a chance mutation were to install a language organ in an evolving bipedal primate, it would be adaptively useless. A very specific social structure—one capable of upholding unusually high levels of public accountability and trust—must have evolved before or concurrently with language to make reliance on "cheap signals" (words) an [[evolutionarily stable strategy]].<ref name="Savage-Rumbaugh 1988">{{Cite book | last1=Savage-Rumbaugh | first1=Sue | last2=McDonald | first2=Kelly | title=Deception and social manipulation in symbol-using apes |editor1=Richard W Byrne |editor2=Andrew Whiten | work=Machiavellian intelligence : social expertise and the evolution of intellect in monkeys, apes, and human | year=1988 | publisher=Clarendon Press | location=Oxford | isbn=978-0-19-852175-4 | oclc=17260831 | pages=224–237}}</ref>