FIGURE 5.5 Schedules of Reinforcement and Response Patterns Different patterns of responding are produced by the four basic schedules of reinforcement. (Left:) The predictable nature of a fixed-ratio schedule (the red line) produces a high rate of responding, with a pause after the reinforcer is delivered. The unpredictable nature of variable-ratio schedules (purple) also produces high, steady rates of responding, but with hardly any pausing between reinforcers. (Right:) Fixed-interval schedules (red) produce a scallop-shaped pattern of responding. The unpredictable nature of variable-interval schedules (purple) produces a moderate but steady rate of responding.

Data from Skinner (1961).