Overview of the simulation models
I present five online models on this site:The Public Goods simulation is a multi agent model consisting of altruists (= C or cooperators) and egoists (= D or defectors) in a group-structured population. Altruists contribute to the common pot of the group, which is then distributed equally among all group members. However, altruists incur costs as a result of their contribution, which means they have less net income than the egoists in their group. From an evolutionary perspective, altruists always seem to be inferior to egoists. However, the simulation shows that this does not have to be the case if the population is divided into groups with limited exchange and selection is based on a global threshold value.
The Matrix Games simulation is also a multi agent model with group-structured populations and global thresholds, here as a mortality function. However, there is no group pot; instead, altruists and egoists earn points through individual interactions with other group members. The points awarded are determined by the payoff matrices commonly used in game theory.
The Cellular Automata work with payoff matrices like the Matrix Games. Here, however, interactions only take place with the up to eight neighbors that each agent, or in this case cell, has.
Altruistic Suicide is a simulation with agents who show a certain willingness to sacrifice their lives for the group. This is again a multi-agent model, but with agents who are neither purely selfish nor altruistic, but have a certain innate tendency (probability) toward self-sacrifice. Every group needs a few self-sacrificing individuals in order to survive.
The Naked Ape simulation is based on a thought experiment that I came up during the coronavirus pandemic, namely that humans' lack of body hair may have evolved for the benefit of the group, enabling them to better detect signs of disease and thus prevent the spread of epidemics within the group. The simulation model demonstrates that this can happen almost automatically when the population is structured.
Similarities and differences between the models
Population is structured in groups or interacts with neighbors. In the multi-agent models, the Group size is limited and surplus offspring migrate to other groups or die.
Asexual reproduction with some mutation. All survivors produce the same number of offspring with a certain probability of mutation.
Selection pressure is only on individuals and the same for everyone. In most of the models shown here, agents receive scores from interactions with others or as shares of the group benefit, which are then compared to a threshold value. Only the “Altruistic Suicide” model deviates from this and uses the ratio of martyrs in the group as a criterion.
No mutual recognition or preferences for traits or relatives. None of the agents have green beards ;-)
No competition between groups. None of the presented models involve competition between the groups. So we are not dealing with group selection here, as this concept is based on this type of competition. Of course, this does not mean that group competition cannot contribute to altruism, only that it is not necessary.
Migration. Except in the cellular automaton, migration can be freely selected so that surplus offspring can only migrate to empty or not fully occupied groups, but purely random migration can also be examined.
Pure or mixed strategy. In most models, the type is innate, so for example C are always altruistic and D are always selfish, so this is a pure strategy. The “altruistic suicide” model, on the other hand, pursues a mixed strategy. Here, only the probability of sacrificing oneself is inherited and the agents behave altruistically only with a certain probability.
Others-only vs. whole-group. A distinction is made between altruistic traits that benefit the entire group, including the altruist themselves, and those that only benefit others. Joint hunting with prey sharing, for example, is of the whole-group type, while alarm calls are more of the others-only type. The "Public Goods" model is of type whole-group, while the models "Altruistic Suicide" and "Naked Ape" are others-only. With "Matrix Games" and "Cellular Automata", it depends on the values in the payout matrix.