Final answer:
Social behaviour where the "actor" benefits at the expense of the "recipient" is termed selfish behaviour, exemplified by the free rider problem. Reciprocal altruism is a cooperation where both parties benefit over time, such as monkeys mutually grooming.
Step-by-step explanation:
The social behaviour in which the "actor" benefits at the expense of the "recipient" is termed selfish behaviour. When individuals behave in a manner that improves their own fitness while potentially harming the fitness of others, it fits this concept. This contrasts with altruistic behaviour, where the actor may suffer a cost to benefit another individual. An example of selfish behaviour is the free rider problem, where someone benefits from a resource or service without contributing to its provision. This can lead to negative outcomes if all individuals act selfishly, as in a group project where everyone decides not to contribute, resulting in a collective failure.
Conversely, reciprocal altruism is a type of behaviour where the exchange of beneficial acts occurs with the expectation of a return in the future. In this cooperation, both parties eventually benefit. Examples include monkeys grooming each other or animals warning others of predators.