CHANGEOVER RATIO EFFECTS ON CONCURRENT VARIABLE‐INTERVAL PERFORMANCE 1

Abstract

Rats' bar‐pressing was maintained by concurrent variable‐interval schedules of reinforcement. A fixed‐ratio of pulls on a chain (the changeover ratio) was required for switching between schedules. The first experiment employed equal variable‐interval schedules and symmetrical changeover ratios. Increasing these ratios resulted in a decrease in the rate of switching between schedules and an increase in local response rate. In the second experiment, a range of asymmetrical changeover ratios was used with equal variable‐interval schedules, and a preference was found for the schedule associated with the larger switching‐into ratio. Both the distributions of responses and time between the two schedules deviated from those expected on the basis of obtained reinforcers. In the third experiment, the switching‐out‐of ratio was dependent on the amount of time spent in a variable‐interval 2‐minute schedule; a constant ratio permitted switching out of the alternative variable‐interval 1‐minute schedule. A strong preference was shown for the variable‐interval 2‐minute schedule. The fourth experiment used equal variable‐interval schedules; one changeover ratio was varied while the second remained constant. The results failed to show systematic differences in local response rates immediately after a changeover.