Figure 4.8 Cumulative Records for Fixed-Interval and Variable-Interval Schedules of Partial Reinforcement As in Figure 4.7, the tick marks indicate when reinforcers were delivered for each of the two schedules. The flat sections following reinforcements for the fixed-interval schedule indicate periods when little or no responding occurred. Such pauses do not occur for a variable-interval schedule. A variable-interval schedule leads to steady responding.