A reinforcement schedule where the first response after a specific, unchanging period of time is rewarded. This creates a scalloped pattern of responding with low rates immediately after reinforcement and increasing rates as the interval ends.
Created by B.F. Skinner in the 1950s from Latin 'fixus' (unchanging) and 'intervallum' (space between). Skinner observed that organisms learn to time their responses, showing minimal effort early in the interval and increased activity near the end.
Fixed interval schedules perfectly explain student behavior - studying drops to nearly zero right after an exam and gradually increases as the next test approaches! Your brain becomes remarkably good at timing when effort will actually pay off.
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