Reciprocal cooperation – Norway rats (Rattus norvegicus) as an example

Many animals cooperate even with unrelated individuals in various contexts, like providing food or allogrooming others. One possibility to explain the evolution of such apparently altruistic behaviour is reciprocity. In reciprocal cooperative interactions, individuals help those partners that have been previously cooperative and therefore exchange favours. This conditional help follows rules like “I help you because you helped me”. These rules are often assumed to be so cognitively demanding that they may be limited to humans. In this chapter, I will shed light on the cognitive underpinnings of reciprocal cooperation by reviewing work on one of the yet best-studied animal in this research area, the Norway rat ( Rattus norvegicus ). Various studies have demonstrated that Norway rats reciprocally exchange different goods and services. They most likely form attitudes towards social partners that are based on the cooperation level of the last encounter, which they remember over long time spans. Cooperation decisions based on attitudes appear cognitively less complex than calculations of received and given favours. Thus, reciprocal cooperation based on this cognitive mechanism might be in fact more widespread among non-human animals than commonly believed.