Question

How decision theory differ from oyher theoriues?

Answer 1

Decision theory is the study of how an agent can maximize its expected utility in situations where there are no other agents making choices.  The sorts of problems studied in a principles of microeconomics course are the sorts of problems that decision theory is concerned with.Game theory is the study of how agents can maximize their expected utility in situations where multiple agents make choices, and the payoff function of each agent depends on what all of the other agents do.  The prisoner's dilemma is the prototypical example of a game theoretic problem.