This article states that in assessing of mental deficiency states appeared and developed formative orientation of develops knowledge and psychological evaluation activities Hereby this orientation aims quantitative aspect, that is any signs of delays in development , as well as qualitative aspect, imbalances and disharmonies. Also Formative Orientation aims perspective forecast investigated child and seeks to provide ways for individual therapeutic intervention developing programs. Formative Orientation in child knowledge is based on its training exercises and tests including manual activities, play and especially learning activities during which children receive comments and encouragements from the psychologist. The latter observes and analyzes changes that occur in the child's behavior investigated, looking for outlight the dynamics of psychic phenomena.