An analysis of interactions in a multiple schedule.

Multiple schedules of reinforcement may bring several different rates of responding under the control of several different exteroceptive stimuli (Ferster & Skinner, 1957). Occasionally, the rate of responding during the presentation of one of the stimuli may be altered by changing only the schedule of reinforcement associated with one of the other stimuli (e.g., Herrnstein Q9 Brady, 1958). A change in the rate of responding during the presentation of one stimulus, brought about by changing the schedule of reinforcement associated with a different stimulus, is called an interaction. Interactions may be studied by reinforcing an organism on a sequence of two-component multiple schedules. For example, suppose a multiple schedule in which both components are variable-interval reinforcement (mult VI VI) is changed to a multiple schedule in which the first component is variable-interval reinforcement and the second component is extinction (mult VI EXT). In the first component of these two multiple schedules, responding is continually reinforced on the same schedule, whereas in the second component the schedule is changed from reinforcement to extinction. When the second component is changed from reinforcement to extinction, the rate of responding in the first component (maintained on the VI schedule) may be unaffected, or it may increase or decrease. If the rate of responding in the first component increases or decreases when the other component becomes extinction, the components of the multiple schedule are said to interact. The sequence of schedules, mult VI VI, mult VI EXT, may reveal another interaction: the extinction curve in the second component ma-y itself differ from extinction curves obtained under different conditions. The present experiment systematically studies the possible interactions in a two-component multiple schedule. In the first series of procedures, the component schedules in the multiple schedule were either reinforcement on a variable-interval schedule (mean interval of 3 minutes) or extinction (VI series). In the second series, the component schedules were either reinforcement on a variable-ratio schedule (150 to 1) or extinction (VR series).