Interaction research has two goals: a theoretical one and a practical one. The theoretical goal is to discover which factors determine the effectiveness of interaction with technology. The applied goal is to provide designers of technology with recommendations on how they must design them. In order to reach both goals, academic and industrial practitioners traditionally have used methodologies that assume the interface and the user can be studied separately as the only means to discover the rules that relate them. However, empirical evidence shows that interaction is the result of the joint work of human cognitive functions (top–down processes) and system characteristics (bottom–up processes). This joint work implies that the human and the technology depend on each other and cannot be studied separately. Therefore, a methodology is needed that takes into account this mutual dependency of human cognitive functions and system characteristics. Finding such methodology is a task for current and future interaction research.