Agency and rationality: Adopting the intentional stance toward evolved virtual agents

The interpretation of other agents as intentional actors equipped with mental states has been connected to the attribution of rationality to their behavior. But a workable definition of "rationality" is difficult to formulate in complex situations, where standard normative definitions are difficult to apply. In this study, we explore a notion of rationality based on the idea of evolutionary fitness. We ask whether agents that are more adapted to their environment are, consequently, perceived as more rational and intentional. We created a 2-D virtual environment populated with autonomous virtual agents, each of which behaves according to a built-in program equipped with simulated perception, memory, and decision making. We then introduced a process of simulated evolution that pressured the agents' programs toward behavior more adapted to the simulated environment. We showed these agents to human subjects in 2 experiments, in which we respectively asked them to judge their intelligence and to dynamically estimate their "mental states." The results confirm that subjects construed evolved agents as more intelligent, and judged evolved agents' mental states more accurately, relative to nonevolved agents. These results corroborate a view that the interpretation of agent behavior is connected to a concept of rationality based on the apparent fit between an agent's actions and its environment.