Final answer:
In game theory, a 'best response' is a strategy that results in the greatest payoff for a player, given the other players' strategies. It can be cooperative or selfish, depending on what maximizes that player's benefit in the game.
Step-by-step explanation:
A "best response" in game theory is a strategy that yields the highest benefit given the strategies chosen by other players in the game. In other words, given a player's beliefs or knowledge about the strategies of other players, a best response is the strategy that maximizes that player's payoff. This concept is crucial in understanding how rational players make decisions in strategic situations, like the prisoner's dilemma or the ultimatum game. Choosing the best response does not necessarily mean being selfish or uncooperative; in many cases, cooperation may be a best response if it leads to a higher payoff for all parties involved. Game theory often reveals that self-interested behavior does not always lead to the best outcomes, and that cooperative behavior can be beneficial in achieving the goals of the group, despite the temptation to act solely in one's own interest.