Recent work on the theory of teams and team reasoning in game interactive settings is due principally to the late Michael Bacharach ( Bacharach, 2006 ), who offers a conception of the individual as a team member, and also to Martin Hollis (1998) and Robert Sugden and Natalie Gold ( Sugden, 2000 ; Gold & Sugden, 2007 ), and is motivated by the conflict between what ordinary experience suggests people often to do and what rationality prescribes for them, such as in prisoner's dilemma games where individuals can choose to cooperate or defect. The source of the conflict, they suggest, is an ambiguity in the syntax of standard game theory, which is taken to pose the question individuals in games ask themselves as, “what should I do?,” but which might be taken to pose the question, particularly when individuals are working together with others as, “what should we do?” When taken in the latter way, each individual chooses according to what best promotes the team's objective and then performs the role appropriate as a member of that team or group. Bacharach understood this change in focus in terms of the different possible cognitive frames that individuals use to think about the world and developed a variable frame theory for rational play in games in which the frame adopted for a decision problem determines what counts as rational play ( Janssen, 2001 ; Casajus, 2001 ).In order to explain how someone acts, we have to take account of the representation or model of her situation that she is using as she thinks what to do. The model varies with the cognitive frame in which she does her thinking. Her frame stands to her thoughts as a set of axes does to a graph; it circumscribes the thoughts that are logically possible for her (not ever, but at that time). ( Bacharach, 2006, p. 69 )Sugden understands this framing idea in terms of the theory of focal points following Thomas Schelling's emphasis on the role of salience in coordination games ( Schelling, 1960 ), and his theory similarly ties decision-making to the way the game is understood ( Sugden, 1995 ). This all recalls what Tversky and Kahneman (1981, 1986) termed standard's theory's description invariance assumption, whose abandonment makes it possible to bring a variety of the insights from psychology to bear on rationality in economics.
