Significance of sincerity insincerity problem for interpersonal relations is considered. Its insufficient research in psychological science and inefficiency of existing methods of detecting of objective truthfulness falsity as closely related psychological analogs to speaker's sincerity insincerity are marked. Essentially new approach to sincerity insincerity indentification on the basis of speaker's coefficients of correspondence of different elements of nonverbal behavior ratings' calculations is proposed. The results of the conducted by the authors' experimental researches are presented. Psychophysiological mechanism underlying identification of speaker's sincerity insincerity, conventionally named by the authors as "psychological detector of lie", is described.