What characterizes a fixed-ratio schedule in operant conditioning?

A fixed-ratio schedule in operant conditioning is characterized by the fact that a response is reinforced only after a specified number of responses. This means that the organism must perform a set number of desired behaviors before receiving a reward. For example, a worker may receive a paycheck after every ten completed tasks. This schedule tends to produce a high rate of response because the subject knows exactly how many behaviors are required to earn the reinforcement, often resulting in a "pause-and-run" pattern, where the subject responds quickly to reach the required number and then takes a brief break after receiving the reward.

The other options describe different types of reinforcement schedules. A variable-ratio schedule involves reinforcement after an unpredictable number of responses, creating a more steady and high response rate. Variable-interval schedules provide reinforcement at variable time intervals, which encourages consistent responses over time but without the exact predictability of a fixed-ratio schedule. Fixed-interval schedules reinforce a response only after a specific time period, leading to a slower response rate as the subject learns to anticipate the reward at the end of the interval.