Final answer:
Game theory is the relevant discipline when an individual's best choice is dependent on the choices of others and vice versa, as it provides the tools for strategic analysis in interdependent decision-making environments.
Step-by-step explanation:
When an individual's best choice depends on what other people choose, and those others' best choices depend on the individual's choice, the science that becomes useful is game theory. Game theory looks at how people make decisions in situations where the outcome depends not just on their own actions, but also on the actions of others. It's a framework for understanding scenarios where the payoffs of one participant depend on the strategies employed by others.
While behavioral economics does consider how individuals make decisions and how psychological factors play a role, it does not specifically address decision-making in strategic environments where one's decisions are interdependent with the decisions of others. Similarly, microeconomics studies the behavior of individuals and firms in making decisions regarding the allocation of resources, but not specifically within interdependent strategic contexts. On the other hand, game theory provides the strategic analysis required for such interdependences.