What is fixed interval scallop?

A fixed interval scallop refers to a pattern of responding observed in operant conditioning, particularly in studies involving fixed interval schedules of reinforcement. In this pattern, subjects show little to no response immediately after reinforcement is provided, followed by a gradual increase in response rate as the interval progresses, culminating in a rapid response just before the next reinforcement is expected. This creates a scalloped shape when graphed, with the "scallops" representing the pauses and bursts of activity in response to the fixed interval schedule.