Which schedule is based on elapsed time rather than the number of responses?

• A. Continuous Reward Schedule
• B. Variable Interval Reward Schedule
• C. Fixed Interval Reward Schedule
• D. Fixed Ratio Reward Schedule

Answer: (C)

Timing controls when reinforcement occurs. In a fixed interval schedule, reinforcement is delivered for the first response after a fixed amount of time has elapsed since the last reinforcement, so the defining factor is elapsed time, not how many responses have occurred. The timer starts after each reward and must reach the set interval before the next response can be reinforced. This differs from continuous reinforcement (every response is rewarded) and from fixed ratio (reward after a set number of responses). A variable interval also uses time, but the interval length varies, making the timing unpredictable. So the scenario described points to a fixed interval schedule.