Fixed Interval (FI) is a schedule of reinforcementReinforcement is a fundamental concept in Applied Behavior Analysis (ABA) and behavioral psychology. It refers to any consequence that follows a behavior and increases the likelihood that the behavior... More in AppliedApplied means that the behaviors targeted for change in ABA are important and meaningful in everyday life, helping to improve the person’s quality of life or social functioning. Example A ... More BehaviorBehavior refers to any activity or action that living organisms engage in, which can be observed, measured, and analyzed. It encompasses all interactions an organism has with its environment, inc... More Analysis (ABA) where reinforcement is delivered for the first responseA response is a single occurrence or instance of a behavior. It refers to a specific action or behavior that happens at a particular moment in time. Example A teacher asks a s... More 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.