This paper examines the possibility of accelerating the development of intelligence when applying stringent Piagetian standards to evaluate the effects of short- and long-term intervention or instruction programs. The paper reviews previous Genevan and American research that shows that development can be accelerated by means of only a few long-term instruction programs that satisfy Piaget's criteria. Successful long-term intervention programs can be based on entirely different theoretical approaches, such as that of the Soviet Obuchova, the American preschool curriculum, or a paradigmatic training method. The only similarity in the different intervention programs is the systematic administration of the training tasks and the repetition of the exercises. However, despite the positive results of several intervention programs, even those of long duration such as Head Start, the effects diminish some time after the program has been discontinued. Studies of identical twins suggest that more permanent changes in the environmental factors influence the development of intelligence to a certain extent. A durable change in the development of intelligence may be invoked only if the environment in which the newly acquired skills have to be exercised has also changed more or less permanently. (Contains 56 references.) (Author/KB)