The phenomenon in behavioural science for humans to behave with more kindness and fairness than would be the case if they behaved rationally. The ultimatum gameis a good example of the principle. Altruism is often linked to the concept of inequity aversion i.e. humans do not like unequal outcomes. Whilst this is usually seen as positive, it can also result in a negative outcome e.g. a person being willing to forego a gain / reward if it means that someone else won’t gain an even better reward.