Which schedule reinforces the first response after a fixed amount of time has passed?

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

Answer: (C)

Fixed Interval schedules reinforce the first response after a fixed amount of time has passed. The key idea is a predictable clock: after the last reinforcement, a set amount of time must elapse, and the next correct response that occurs after that exact interval is rewarded. Because of this timing, the animal often shows a brief pause after reinforcement, then increases responding as the end of the interval approaches, creating a scalloped response pattern.

This differs from other schedules. A fixed ratio reinforcement follows a set number of responses, not a time interval. A variable interval delivers reinforcement at unpredictable times, so there isn’t a fixed waiting period. A variable duration requires the behavior to be maintained for a varying amount of time before reinforcement.