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Interval reinforcement is a group of reinforcement schedules used in learning research. In these schedules the timing of reinforcement is systematically altered to explore is effects upon behavior.

• Fixed interval schedule(FI) - reinforcement of the first response after a fixed time interval has passed since the previous reinforcement (maintaining a fixed interval between reinforcers)
• Variable interval schedule(VI) - reinforcement of the first response after a variable time interval has passed since the previous reinforcement; the schedule is characterised by the mean interval occurring between reinforcements, e.g. VI 30 seconds.