a branch of psychology that studies the principles of disturbances of psychic activity and personality characteristics by comparing them with the principles of the normal formation and development of the personality.

The establishment of pathopsychology was closely associated with the development of psychiatry. At the end of the 19th century the first experimental psychology laboratories in psychoneurology institutions were founded by the German psychologist W. Wundt and by the Russian psychoneurologists V. M. Bekhterev and S. S. Korsakov. The first manuals on the application of the methods of experimental psychology to the study of the mentally ill were published at the beginning of the 20th century. The ideas of L. S. Vygotskii played a major role in the development of pathopsychology in the USSR.

Research in pathopsychology is of great significance for a number of general methodological problems in psychology, such as the question of the relationship between the biological and the social in the development of the psyche. Data from investigations in pathological psychology show that disruption of the personality does not indicate the liberation of biological instincts and needs but is characterized primarily by changes in human motives and needs. It has also been established that the principles of the disintegration of the psyche do not recapitulate in reverse the stages of the psyche’s development.

The results of research in pathopsychology are used in psychiatry as diagnostic criteria and as aids in establishing the degree of intellectual impairment, in making evaluations (forensic, occupational, and military), and in calculating the effectiveness of treatment, especially when prescribing psychopharmacological agents. They are also used in the analysis of disturbances of mental activity associated with hazardous occupations and in deciding how to restore the ability to work.

Pathopsychology applies experimental methods, the basic principle of which is qualitative analysis of psychic disturbances as mediated and motivated activities. A pathopsychological experiment makes it possible to actualize not only the mental operations but also the motives of the patient. In pediatric pathopsychology, a particularly well-developed field, special methods have been elaborated, such as the learning experiment, based on Vygotskii’s proposition of the “zone of proximal development.”