Book excerpt: In recent years, a booming research interest has been observed in linking basic cognitive processes with a variety of social and clinical phenomena. Evidence comes from the increasing popularity of psychological paradigms such as social cognition, cognitive psychopathology or cognitive aging. What links those paradigms is their special focus on explaining cognitive phenomena by use of the concept of mental resources. Immediate reasons for such a focus are found in the growing emphasis on understanding everyday dynamics of thinking and acting within a complex world, as well as within personal constraints. Obviously, our current goals and choice of activities constrain and influence our reasoning as well as the processes of input to and retrieval from memory. Situational demands will act to the same effect, and the interplay between both, internal and external constraints, makes apparent a first and straightforward relevance of the resource notion in action-oriented cognitive research. For example, person perception is a dynamic process depending on what my goals in perception are, what the perceiving situation is that I find myself in, and how complex the target characteristics are. In fact, the amount of resources spent in this process may be reflected in its speed, the quality of the perceptual or mnemonic trace which is being created, or the kind of social or non-social behavior that can be supported.