Evolution of Altruistic Robots

In this document we examine the evolutionary methods that may lead to the emergence of altruistic cooperation in robot collectives. We present four evolutionary algorithms that derive from biological theories on the evolution of altruism in nature and compare them systematically in two experimental scenarios where altruistic cooperation can lead to a performance increment. We discuss the relative merits and drawbacks of the four methods and provide recommendations for the choice of the most suitable method for evolving altruistic robots. 1 Altruistic Cooperation in Nature The competition for survival and reproduction postulated by Darwin seems at odds with the observation that some organisms display cooperative behaviors. In order to understand the evolutionary conditions when cooperation can emerge, Lehmann and Keller [14] suggested to distinguish between two types of cooperation (figure 1), namely the situations where a cooperator does not pay a fitness cost from helping other individuals and the situations where a cooperator must pay a fitness cost for helping other individuals. Let us remember that in biology fitness benefits and costs translate into the number of genetic copies that an individual can produce or loose with respect to its baseline reproduction rate. The situation where cooperation generates a fitness benefit without any cost to the cooperator is relatively common in nature. This situation can be further divided in two cases, when the benefit is immediate or direct and when the benefit is indirect. Examples of cooperation with direct benefits include nest building and group hunting. Whenever a cooperator obtains an immediate and direct benefit from helping another individual, cooperation will always evolve and remain stable, no matter whether the receiving individuals belong to another species or have never been seen before. If the benefit is indirect, i.e., the act of helping is not immediately reciprocated or the benefit appears only in the long term, cooperation evolves only if individuals have an initial tendency to cooperate, interact together several times, and can both recognize the partner and remember the outcome of previous interactions. If these conditions are satisfied, cooperation will always evolve and remain stable even if cooperating individual belong to different species.