A laboratory test of the constant risk hypothesis

It has been repeatedly suggested that subjects aim at maintaining a constant error probability in many variants of self-paced performance and that they adjust their behaviour so as to keep their risks relatively constant. This constant risk hypothesis is investigated in a simple computer-controlled addition task it which subjects manipulated exercise difficulty as a function of their own calculation proficiency and the allotted solution time. Error probability proved to be unrelated to level of skill and to amount of allotted computation time, but to depend onuncertainty with respect to exercise difficulty.