Dynamics of reflexive operations within thinking activity is theoretically considered. It has been assumed that actual-genesis of comprehension of one's own thinking activity can be divided into three stages differing in the degree of explication of a meaningful intention in products of testing behavior. At the first stage reflexive thinking takes form of the estimation and sanctioning. Further, as there form goals, reflexivity turns into a means of control over the goal-achieving processes. At the third stage opportunities for the reflexive control drastically widen due to appearance of the eventual products. The assumption has been experimentally proved.