Identifying Fixed Ratio Reinforcement in Operant Conditioning

In the framework of operant conditioning, behavior modification often involves the use of different types of reinforcement and punishment. In a recent experiment, a researcher conditioned a rat to press a lever in a Skinner box. At first, the rat receives a food pellet every time it successfully presses the lever (this is known as positive reinforcement). Over time, the schedule of reinforcement changes. The researcher then decides to only give the rat a food pellet after every fifth lever press, which is known as: