In a classroom scenario, reinforcement from pop quizzes at unpredictable times illustrates which schedule?

• A. Fixed-Interval Schedule
• B. Variable-Interval Schedule
• C. Fixed-Ratio Schedule
• D. Variable-Ratio Schedule

Answer: (B)

This item is about reinforcement schedules based on timing. When rewards come after varying, unpredictable moments rather than after a set number of actions, behavior tends to stay steady because you never know when the next reward will appear. Pop quizzes fit this pattern because their timing is unpredictable, so students keep studying consistently rather than slowing down until a known quiz date. This describes a variable-interval schedule. In contrast, a fixed-interval schedule yields a clear pause after a reward and a ramp-up as the next reward approaches, and a fixed-ratio or variable-ratio schedule depends on the number of responses, not the passage of time.