Examining selected statistical and modeling approaches in psychology, the book concentrates on the topics of mental test theory and theory of measurement. The main objective is not only to present a critical view of the approaches suggested up until now, but also their reinterpretation, extension and enrichment by new theories and concepts, for example, formal theories of semiotics and knowledge, and a unifying theory of actions.The book also shows a relation between test theory and the foundations of fuzzy set theory. It presents new models of measurement tools and new measurement theories of concepts such as objective and subjective time, risk or utility, and discusses the cognitive foundations of these theories, namely the theory of perception and observability.