Which term refers to reinforcement after a fixed amount of time since the last reinforcement?

• A. Interference
• B. Assimilation
• C. Fixed interval ratio
• D. Attention Deficit Hyperactivity Disorder

Answer: (C)

Reinforcement schedules describe how often rewards follow behavior in operant conditioning. When reinforcement occurs after a fixed amount of time has passed since the last reinforcement, the schedule is fixed interval. The timer starts after each reinforcement, and the first correct response after that fixed interval is rewarded. This tends to produce a scalloped pattern: low responding right after reinforcement, then increasing as the interval nears its end, with a burst of responses once the interval resets and reinforcement occurs. This differs from a fixed-ratio schedule, where reinforcement depends on a set number of responses, not time, and from variable-interval schedules, where the interval length varies unpredictably.