Fixed Interval (FI) is a schedule of reinforcementReinforcement is a fundamental concept in Applied Behavior A... in AppliedApplied means that the behaviors targeted for change in... BehaviorBehavior refers to any activity or action that living o... Analysis (ABA) where reinforcement is delivered for the first responseA response is a single occurrence or instance of a... after a fixed amount of time has passed. Regardless of how many responses occur during the interval, only the first response after the interval ends will be reinforced. This type of schedule typically leads to a pattern of behavior where responses increase as the time for reinforcement approaches.
Example
A teacher uses a Fixed Interval 5-minute schedule (FI 5) to reinforce a student’s on-task behavior. The student receives a sticker for staying on task, but only after 5 minutes have passed, and only if the student shows on-task behavior at that time. During the 5-minute interval, the student may show on-task behavior, but no reinforcement is given until the timer reaches the 5-minute mark. At that point, the first instance of on-task behavior is reinforced with the sticker, and the timer resets for the next interval.