Pioneer of American psychological science and teacher. His interests were focused on child development (pedology) and evolutionary theory. Hall became famous for his studies of the mental development of children. First of all, he drew attention to the importance of studying the process of formation of the psyche of a particular child. Hall also developed the theory of recapitulation, according to which the child in his mental development (ontogenesis) repeats all the stages of the mental development of the human race (phylogeny).