Human beings are agents: They may exert influence over their own fate. They initiate their actions, experience a considerable degree of freedom and control in their mundane activities, and respond adversely to external constraints to their agency; they are able to monitor and modify their moti­ vation, affective states, and behavior. Since the sixties, the notion of person-as-agent has become increas­ ingly accepted in scientific psychology. Nowadays, personal control is a standard topic in research on personality, motivation, and social behavior. The most popular approach identifies personal control with a feeling or judgment: To have control means to perceive the self as a source of causa­ tion. Within this perspective, such consciously accessible contents like perceived freedom and self-determination, feelings and expectations of control, or perceived self-efficacy and competence emerge as natural tar­ gets of research (see e.g., Alloy, Clements, & Koenig, 1993; Bandura, 1977; OeCharms, 1968; Oeci & Ryan, 1985; Harvey, 1976; Rotter, 1966; Thomp­ son, 1993; Wortman, 1975).