Response cost and the control of verbal behavior under free-operant avoidance schedules.

Human subjects were tested in a free-operant avoidance procedure. Shock could be avoided by the emission of a verbal response of adequate intensity and duration. These schedules were found to control the emission of verbal operants in the same way they control motor operants. Some subjects showed conventional control by this schedule with or without response-produced feedback. Other subjects verbalized at a high rate under both these conditions until the addition of response cost brought this behavior under conventional schedule control.