The Great Grounding Game Theory Guide: — How To Get What You Want and Need With Reciprocal Altruism

Collaboration, partnership, and selfish self-fullness to win at the game of life

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Photo by Massimo Sartirana on Unsplash

For an introduction and simple explanation in text and with a short video explanation of the basics of game theory please click below…

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In game theory, reciprocal altruism is a behavior whereby an individual acts in a manner that temporarily reduces personal benefit and fitness while increasing benefits and fitness in another person. Another with the expectation that the other organism will act in a similar manner at a later time. This concept was initially developed by Robert Trivers to explain the evolution of cooperation as instances of mutually altruistic acts. The concept is close to the strategy of “tit for tat” used in game 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. This concept finds its roots in the work of the English evolutionary biologist, W.D. Hamilton, who developed mathematical models for predicting the likelihood of an altruistic act to be performed on behalf of one’s kin.

Putting this into the form of a game theory strategy in a repeated prisoner’s dilemma would mean to cooperate unconditionally in the first period and behave cooperatively (altruistically) as long as the other agent does as well.

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” 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.


An example of reciprocal altruism is cleaning symbioses such as between hosts and the cleaner fish they host upon. Cleaners include birds and shrimp, and clients include mammals, turtles, fish, turtles, and octopuses Aside from the apparent symbiosis of the cleaner and the host during actual cleaning, which cannot be interpreted as altruism, the host displays additional behavior that meets the criteria for reciprocal altruism:

1. The host fish allows the cleaner fish-free entrance and exit,

2. The host does not eat the cleaner, even after the cleaning is done.

3. The host signals the cleaner it is about to depart the cleaner’s locality, even when the cleaner is not in its body.

4. The host sometimes chases off possible predators and dangers to the cleaner.

The following evidence supports the hypothesis:

The cleaning by cleaners is essential for the host. In the absence of cleaners, the hosts leave the locality or suffer from injuries inflicted by ectoparasites. There are difficulties and dangers in finding a cleaner. Hosts leave their element for cleaning elsewhere. Others wait no longer than 30 seconds before searching for cleaners elsewhere.

A key requirement for the establishment of reciprocal altruism is that the same two individuals must interact repeatedly, as otherwise the best strategy for the host would be to eat the cleaner as soon as cleaning was complete. This constraint imposes both a spatial and a temporal condition on the cleaner and on its host.

Both individuals must remain in the same physical location, and both must have a long enough lifespan, to enable multiple interactions. There is reliable evidence that individual cleaners and hosts do indeed interact repeatedly.

This example meets some, but not all, of the criteria described in Trivers’s model. In the cleaner-host system, the benefit to the cleaner is always immediate. However, the evolution of reciprocal altruism is contingent on opportunities for future rewards through repeated interactions. In one study, nearby host fish observed “cheater” cleaners and subsequently avoided them. In these examples, true reciprocity is difficult to demonstrate since failure means the death of the cleaner.

Warning calls, although exposing a bird and putting it in danger, are frequently given by birds. An explanation in terms of altruistic behaviors given by Trivers/

It has been shown that predators learn specific localities and specialize individually on prey types and hunting techniques. It is therefore disadvantageous for a bird to have a predator eat a conspecific because the experienced predator may then be more likely to eat him. Alarming another bird by giving a warning call tends to prevent predators from specializing on the caller’s species and locality. In this way, birds in areas in which warning calls are given will be at a selective advantage relative to birds in areas free from warning calls.

Reciprocal altruism is an essential strategy for long term success. Reciprocation is seldom 100%

and in many scenarios, there is a lack of important elements of reciprocity. Often It is very hard to detect and ostracize cheaters and there is no evidence that a bird refrains from giving calls when another bird is not reciprocating, nor evidence that individuals interact repeatedly. Given the aforementioned characteristics of bird calling, a continuous bird emigration and immigration environment (true of many avian species) are most likely to be partial to cheaters. Much of my work in HAGT is about developing strategies to deal with cheaters and weaken their ability to cheat effectively.

Author: Lewis Harrison is an Independent Scholar with a passion for knowledge, personal development, self-improvement, and problem-solving. He is the creator of Harrison’s Applied Game Theory.

You can read all of his Medium stories at

“I am always exploring trends, areas of interest, and solutions to build new stories upon. Again, if you have any ideas you would like me to write about just email me at”.

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By L Harrison

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I offer advice on the arts, innovation, self-improvement, life lessons, mental health, game theory strategies, and love.

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