Which approach assumes that all actors act rationally based on their interests and capabilities?

The correct approach that assumes all actors act rationally based on their interests and capabilities is rationalism. This theoretical framework emphasizes that individuals and states make decisions by logically weighing their options and the likely outcomes to maximize their benefits and minimize costs. Rationalism is grounded in the belief that actors will pursue their own interests in a systematic manner, considering their capabilities and the context of their interactions.

Rationalism is crucial for understanding international relations, as it provides a lens through which one can analyze state behavior during negotiations, conflicts, and alliances. It encapsulates the idea that the choices made by states or actors are calculated and strategic responses to their interests and the actions of others. This perspective often informs theories that rely on the precept of logic and strategic decision-making in global politics.

Constructivism, while also a significant theory in international relations, focuses more on the social constructs, identities, and the roles of norms in shaping behavior, which contrasts with the rationalist approach. Realism shares some similarities with rationalism, particularly in recognizing state interests and power, but it places a stronger emphasis on the anarchic nature of international relations. Behaviorism, on the other hand, analyzes observable behaviors of actors without necessarily ascribing rational decision-making processes to them.