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.