The present study examined the effects of a new mode of reinforcement, the 'Alien' mode of Reinforcement(AR), as compared to a External one(ER)and a double reinforcement(EAR). In Exp.I, 60 children and 30 adolescents were asked to perform high discrimination tasks under either of the 3 conditions mentioned above. Subjects were 3rd and 6th graders in a primary school and 3rd graders in a junior high school. In Exp.II, under the same 3 conditions as in Exp.I, a task of choosing one among four given words was administered to 72 adolescents belonging to 2nd grade in junior(J2) and senior high(H2) schools. While fairly stable effects were found in ER and EAR conditions, no significant effects of AR condition on learning were found except in H2 group of Exp.II. Taking account of the findings of Haruki, et al.(1979), AR seems to become fully effective, in developmental phase, somewhere between senior high school and university.