Which schedule uses a reinforcer after a variable number of responses?

• A. Fixed Ratio (FR) Reinforcement
• B. Variable Ratio (VR) Reinforcement
• C. Fixed Interval (FI) Reinforcement
• D. Variable Interval (VI) Reinforcement

Answer: (B)

The key idea here is how reinforcement is scheduled: it’s about when a reinforcement is delivered in relation to responses, not just time. A Variable Ratio schedule delivers reinforcement after an unpredictable number of responses, with the average set by the program. Because the required number of responses changes around that average, the learner can’t predict exactly when the next reinforcement will come, so they keep responding quickly and persistently.

That explains why this option is the best fit: reinforcement is tied to the count of responses, and that count is variable. You get a high, steady rate of responding and little or no noticeable pause after reinforcements.

In contrast, a Fixed Ratio schedule gives reinforcement after a set number of responses, which often creates a noticeable post-reinforcement pause and a pattern of bursts of responding. A Fixed Interval schedule reinforces the first response after a fixed amount of time, so you get low activity near the end of the interval and a reset after reinforcement. A Variable Interval schedule delivers reinforcement after an unpredictable amount of time, independent of the number of responses, leading to steady but typically lower responding than a Variable Ratio schedule.