From its earliest beginnings, American conditioning research using human subjects had to deal with the possibility that subjects might voluntarily control the reaction that the experimenter attempts to condition, with the result that voluntary control contaminates the study of conditioning in humans. A preliminary solution to the problem was achieved around 1940, ending the time frame of this survey. This article provides an historical survey of the conceptual background of the opposition of volition and reflexes; describes manifestations of the problem (...) in conditioning research; and critically examines earlier efforts to solve the problem as well as the presumptive solution that disposed of the issue by 1940. Lessons from this story are adduced. (shrink)