Cooperation (written as co-operation in British English) is the process of groups of organisms working or acting together for common, mutual, or some underlying benefit, as opposed to working in competition for selfish benefit. Many animal and plant species cooperate both with other members of their own species and with members of other species (symbiosis or mutualism).
Humans cooperate for the same reasons as other animals: immediate benefit, genetic relatedness, and reciprocity, but also for particularly human reasons, such as honesty signaling (indirect reciprocity), cultural group selection, and for reasons having to do with cultural evolution.
Language allows humans to cooperate on a very large scale. Certain studies have suggested that fairness affects human cooperation; individuals are willing to punish at their own cost (altruistic punishment) if they believe that they are being treated unfairly.Sanfey, et al. conducted an experiment where 19 individuals were scanned using MRI while playing an ultimatum game in the role of the responder. They received offers from other human partners and from a computer partner. Responders refused unfair offers from human partners at a significantly higher rate than those from a computer partner. The experiment also suggested that altruistic punishment is associated with negative emotions that are generated in unfair situations by the anterior insula of the brain.
It has been observed that image scoring, where a participant learns of their counterpart's prior behavior or reputation, promotes cooperative behavior in situations where direct reciprocity is unlikely. This implies that in situations where reputation and status are involved, humans tend to cooperate more.
Cooperation is common in non-human animals. Besides cooperation with an immediate benefit for both actors, this behavior appears to occur mostly between relatives. Spending time and resources assisting a related individual may at first seem destructive to the organism's chances of survival but is actually beneficial over the long-term. Since relatives share part of their genetic make-up, enhancing each other's chances of survival may actually increase the likelihood that the helper's genetic traits will be passed on to future generations. The cooperative pulling paradigm is an experimental design used to assess if and under which conditions animals cooperate. It involves two or more animals pulling rewards towards themselves via an apparatus they can not successfully operate alone. Some researchers assert that cooperation is more complex than this. They maintain that helpers may receive more direct, and less indirect, gains from assisting others than is commonly reported. Furthermore, they insist that cooperation may not solely be an interaction between two individuals but may be part of the broader goal of unifying populations.