The book contains the most significant works for psychological science and practice by one of the leading Russian specialists in the field of differential psychology. It presents works devoted to the problems of professional suitability depending on the basic properties of the human nervous system, outlines the author’s vision of the problems of studying the personal and mental development of schoolchildren through a new type of criterion-oriented tests, and also discusses the prospects for using the developed methods for organizing feedback in educational institutions. Publication intended primarily for specialists in the field of general and differential psychology, those who deal with the problems of individual differences and the creation of psychological tools, practicing psychologists who resolve issues of personnel selection and psychological assistance in solving problems of human effectiveness as a subject of a particular professional activity. The materials in the book may be useful to practical psychologists, teachers and students studying psychology.