Fixed interval reinforcement (FI) is a reinforcement schedule in operant conditioning that delivers reinforcement for the first response after a fixed length of time since the last reinforcement, while premature responses are not reinforced.
- Example: FI1" = reinforcement provided for the first response after 1 second
- Lab example: FI15" = rat is reinforced for the first bar press after 15 seconds passes since the last reinforcement
- Real world example: FI24 hour = calling a radio station is reinforced with a chance to win a prize, but the person can only sign up once per day