Editing Reciprocal altruism (section)

==Theory==
The concept of "reciprocal altruism", as introduced by Trivers, suggests that [[altruism]], defined as an act of helping another individual while incurring some cost for this act, could have evolved since it might be beneficial to incur this cost if there is a chance of being in a reverse situation where the individual who was helped before may perform an altruistic act towards the individual who helped them initially.<ref name="trivers">{{cite journal | last1 = Trivers | first1 = R.L. | year = 1971 | title = The evolution of reciprocal altruism | journal = Quarterly Review of Biology | volume = 46 | pages = 35–57 | doi = 10.1086/406755 | s2cid = 19027999 }}</ref> This concept finds its roots in the work of [[W. D. Hamilton|W.D. Hamilton]], who developed mathematical models for predicting the likelihood of an altruistic act to be performed on behalf of one's kin.<ref>{{Cite journal|last=Hamilton|date=1964|title=The Genetical Evolution of Social Behavior II|journal=Journal of Theoretical Biology|volume=7|issue=1|pages=17–52|doi=10.1016/0022-5193(64)90039-6|pmid=5875340|bibcode=1964JThBi...7...17H }}</ref>

Putting this into the form of a strategy in a repeated [[prisoner's dilemma]] would mean to [[Cooperation|cooperate]] unconditionally in the first period and behave cooperatively (altruistically) as long as the other agent does as well.<ref name="trivers" /> If chances of meeting another reciprocal altruist are high enough, or if the game is repeated for a long enough amount of time, this form of altruism can evolve within a population.

This is close to the notion of "[[tit for tat]]" introduced by [[Anatol Rapoport]],<ref name=Dawkins06>{{cite book |author-link=Richard Dawkins |first=Richard |last=Dawkins |title=The Selfish Gene |edition=30th Anniversary |publisher=Oxford University Press |year=2006 |isbn=0-19-929114-4 }}</ref> although there still seems a slight distinction in that "tit for tat" cooperates in the first period and from thereon always replicates an opponent's previous action, whereas "reciprocal altruists" stop cooperation in the first instance of non-[[cooperation]] by an opponent and stay non-cooperative from thereon. This distinction leads to the fact that in contrast to reciprocal altruism, tit for tat may be able to restore cooperation under certain conditions despite cooperation having broken down.

Christopher Stephens shows a set of necessary and jointly sufficient conditions "... for an instance of reciprocal altruism:<ref name="Stephens">{{cite journal | last1 = Stephens | first1 = C. | year = 1996 | title = Modelling Reciprocal Altruism | journal = British Journal for the Philosophy of Science | volume = 47 | issue = 4| pages = 533–551 | doi = 10.1093/bjps/47.4.533| s2cid = 1462394 }}</ref>

# the behaviour must reduce a donor's fitness relative to a selfish alternative;<ref name="Stephens"/>
# the fitness of the recipient must be elevated relative to non-recipients;<ref name="Stephens"/>
# the performance of the behaviour must not depend on the receipt of an immediate benefit;<ref name="Stephens"/>
# conditions 1, 2, and 3 must apply to both individuals engaging in reciprocal helping.<ref name="Stephens"/>

There are two additional conditions necessary "...for reciprocal altruism to evolve:"<ref name="Stephens"/>

* A mechanism for detecting 'cheaters' must exist.<ref name="Stephens"/>
* A large (indefinite) number of opportunities to exchange aid must exist.<ref name="Stephens"/>

The first two conditions are necessary for altruism as such, while the third is distinguishing reciprocal altruism from simple mutualism and the fourth makes the interaction reciprocal.
Condition number five is required as otherwise non-altruists may always exploit altruistic behaviour without any consequences and therefore evolution of reciprocal altruism would not be possible. However, it is pointed out that this "conditioning device" does not need to be conscious. Condition number six is required to avoid cooperation breakdown through forward induction&mdash;a possibility suggested by game theoretical models.<ref name="Stephens" />

In 1987, Trivers told a symposium on reciprocity that he had originally submitted his article under the title "The Evolution of Delayed Return Altruism", but reviewer W. D. Hamilton suggested that he change the title to "The Evolution of Reciprocal Altruism". Trivers changed the title, but not the examples in the manuscript, which has led to confusion about what were appropriate examples of reciprocal altruism for the  last 50 years. In their contribution to that symposium, Rothstein and Pierotti (1988)<ref name="rothstein and pierotti">{{cite journal |last1=Rothstein |first1=S. I. |year=1988 |title=Distinctions among reciprocal altruism and kin selection, and a model for the initial evolution of helping behavior |journal=Ethology and Sociobiology |volume=9 |pages=189–210 |doi=10.1016/0162-3095(88)90021-0}}</ref> addressed this issue and proposed new definitions concerning the topic of altruism, that clarified the issue created by Trivers and Hamilton. They proposed that Delayed Return Altruism was a superior concept and used the term pseudo-reciprocity in place of DRA.{{Citation needed|date=November 2024}}