Which schedule delivers a reinforcer after the first response following a variable amount of time since the last reinforcement?

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

Answer: (B)

This describes a time-based, unpredictable reinforcement pattern. In interval schedules, reinforcement is tied to the passage of time since the last reinforcement, and you get reinforced on the first response after that interval ends. When the interval is variable, the exact amount of time fluctuates, so the reinforcer is delivered after a changing amount of time, still gated by the first response after that interval. That matches the scenario: the reinforcer comes after the first response once a variable amount of time has passed since the previous reinforcement. This leads to steady, moderate responding because the exact timing is unpredictable. If the interval were fixed, the timing would be predictable and responses typically peak near the end of the interval. If it were a ratio schedule (fixed or variable), reinforcement would depend on the number of responses, not the passage of time.