This is a longitudinal study of a hierarchical organization of the psychological development of an infant as measured by the seven ordinal scales of Uzgiris and Hunt. Six branches of development were studied: "the development of visual pursuit and the permanence of objects", "the development of means for obtaining desired environmental events", "the construction of object relations in space", "the development of operational causality", "the development of schemes for relating to objects", and "the development of vocal imitation and the development of gestural imitation"; the sequential ordinality of psychological development was proved, except in a few instances. Moreover, the findings suggested that besides more independence in development along the six branches a psychological development in the sensory-motor period, especially early, proceeded a given achievement in a branch, and thus affecting the achievement of a later organized landmark in other branches.