Taken together, the evidence suggests that the Kuba state is associated with a deterioration of intrinsic motivations to follow the rules. This does not mean that the Kuba Kingdom was not a successful and well-functioning state. From the historical and anthropological literature, we know that it was. Although the state was prosperous and orderly, the evidence suggests that it eroded the intrinsic propensity of its subjects to follow rules even when enforcement is absent. (28)

Here (pdf)