Almost all psychological research relevant to revolutions focuses on the conditions in which collective action takes place to topple the ruling regime; almost no attention has been given to what happens after revolutions. Psychologists have homed in on relative deprivation, perceived injustice, identity processes, morality, and related factors as important in collection mobilization. But no serious attention has been given to the question of why after regime change almost all revolutionary governments fail to change mass behavior in line with their revolutionary ideals. The concept of political plasticity is applied in this chapter to explain this failure. Change at the macropolitical and macroeconomic levels can come overnight with the signing of a radical new constitution, but change of actual behavior in line with the ideals of the new constitution takes a much longer time, if it is possible at all. An example is the efforts of the Soviet communists to change behavior in line with their economic and political ideals of collective ownership and collective motivation.