Which term describes reinforcement delivered after a variable amount of time since the last reinforcement opportunity, regardless of responses?

• A. Fixed Interval Reinforcement
• B. Variable Interval Reinforcement
• C. Fixed Ratio Reinforcement
• D. Variable Ratio Reinforcement

Answer: (B)

Understanding reinforcement schedules means looking at what triggers the next reinforcement: time or responses, and whether that trigger is fixed or variable. When reinforcement is delivered after a variable amount of time has passed since the last reinforcement opportunity, and it happens regardless of whether the target behavior occurred, that's a variable interval schedule. The variability in time makes the next reward unpredictable, which tends to produce a steady, moderate rate of responding with little to no post-reinforcement pause, because there’s no predictable moment when reinforcement will come. In contrast, a fixed interval would deliver after a set time and typically show a post-reinforcement pause with responding increasing as the interval nears its end; a fixed ratio requires a set number of responses before reinforcement; a variable ratio delivers reinforcement after an unpredictable number of responses, often producing a high, steady rate of responding.