What schedule reinforces the first response after a set amount of time has passed?

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

Answer: (C)

Fixed interval reinforcement delivers a reward for the first response after a set amount of time has passed. After you give the reinforcement, the timer resets, and only the first response once the interval ends gets reinforced. If the animal responds during the interval, those responses aren’t rewarded, so you often see a short pause after reinforcement followed by increasing responding as the end of the interval nears. This pattern contrasts with schedules that depend on the number of responses (a fixed ratio pays after a set number of responses; a variable ratio pays after an unpredictable number) or with schedules that reward after varying times (a variable interval).